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linux/kernel/bpf/verifier.c
Paul Chaignon 927cb78177 bpf: remove incorrect 'verifier bug' warning 
The BPF verifier checks the maximum number of call stack frames twice,
first in the main CFG traversal (do_check) and then in a subsequent
traversal (check_max_stack_depth).  If the second check fails, it logs a
'verifier bug' warning and errors out, as the number of call stack frames
should have been verified already.

However, the second check may fail without indicating a verifier bug: if
the excessive function calls reside in dead code, the main CFG traversal
may not visit them; the subsequent traversal visits all instructions,
including dead code.

This case raises the question of how invalid dead code should be treated.
This patch implements the conservative option and rejects such code.

Signed-off-by: Paul Chaignon <paul.chaignon@orange.com>
Tested-by: Xiao Han <xiao.han@orange.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2019-03-26 13:02:16 -07:00

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/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
* Copyright (c) 2016 Facebook
* Copyright (c) 2018 Covalent IO, Inc. http://covalent.io
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of version 2 of the GNU General Public
* License as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*/
#include <uapi/linux/btf.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/bpf.h>
#include <linux/btf.h>
#include <linux/bpf_verifier.h>
#include <linux/filter.h>
#include <net/netlink.h>
#include <linux/file.h>
#include <linux/vmalloc.h>
#include <linux/stringify.h>
#include <linux/bsearch.h>
#include <linux/sort.h>
#include <linux/perf_event.h>
#include <linux/ctype.h>
#include "disasm.h"
static const struct bpf_verifier_ops * const bpf_verifier_ops[] = {
#define BPF_PROG_TYPE(_id, _name) \
[_id] = & _name ## _verifier_ops,
#define BPF_MAP_TYPE(_id, _ops)
#include <linux/bpf_types.h>
#undef BPF_PROG_TYPE
#undef BPF_MAP_TYPE
};
/* bpf_check() is a static code analyzer that walks eBPF program
* instruction by instruction and updates register/stack state.
* All paths of conditional branches are analyzed until 'bpf_exit' insn.
*
* The first pass is depth-first-search to check that the program is a DAG.
* It rejects the following programs:
* - larger than BPF_MAXINSNS insns
* - if loop is present (detected via back-edge)
* - unreachable insns exist (shouldn't be a forest. program = one function)
* - out of bounds or malformed jumps
* The second pass is all possible path descent from the 1st insn.
* Since it's analyzing all pathes through the program, the length of the
* analysis is limited to 64k insn, which may be hit even if total number of
* insn is less then 4K, but there are too many branches that change stack/regs.
* Number of 'branches to be analyzed' is limited to 1k
*
* On entry to each instruction, each register has a type, and the instruction
* changes the types of the registers depending on instruction semantics.
* If instruction is BPF_MOV64_REG(BPF_REG_1, BPF_REG_5), then type of R5 is
* copied to R1.
*
* All registers are 64-bit.
* R0 - return register
* R1-R5 argument passing registers
* R6-R9 callee saved registers
* R10 - frame pointer read-only
*
* At the start of BPF program the register R1 contains a pointer to bpf_context
* and has type PTR_TO_CTX.
*
* Verifier tracks arithmetic operations on pointers in case:
* BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),
* BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -20),
* 1st insn copies R10 (which has FRAME_PTR) type into R1
* and 2nd arithmetic instruction is pattern matched to recognize
* that it wants to construct a pointer to some element within stack.
* So after 2nd insn, the register R1 has type PTR_TO_STACK
* (and -20 constant is saved for further stack bounds checking).
* Meaning that this reg is a pointer to stack plus known immediate constant.
*
* Most of the time the registers have SCALAR_VALUE type, which
* means the register has some value, but it's not a valid pointer.
* (like pointer plus pointer becomes SCALAR_VALUE type)
*
* When verifier sees load or store instructions the type of base register
* can be: PTR_TO_MAP_VALUE, PTR_TO_CTX, PTR_TO_STACK, PTR_TO_SOCKET. These are
* four pointer types recognized by check_mem_access() function.
*
* PTR_TO_MAP_VALUE means that this register is pointing to 'map element value'
* and the range of [ptr, ptr + map's value_size) is accessible.
*
* registers used to pass values to function calls are checked against
* function argument constraints.
*
* ARG_PTR_TO_MAP_KEY is one of such argument constraints.
* It means that the register type passed to this function must be
* PTR_TO_STACK and it will be used inside the function as
* 'pointer to map element key'
*
* For example the argument constraints for bpf_map_lookup_elem():
* .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL,
* .arg1_type = ARG_CONST_MAP_PTR,
* .arg2_type = ARG_PTR_TO_MAP_KEY,
*
* ret_type says that this function returns 'pointer to map elem value or null'
* function expects 1st argument to be a const pointer to 'struct bpf_map' and
* 2nd argument should be a pointer to stack, which will be used inside
* the helper function as a pointer to map element key.
*
* On the kernel side the helper function looks like:
* u64 bpf_map_lookup_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
* {
* struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
* void *key = (void *) (unsigned long) r2;
* void *value;
*
* here kernel can access 'key' and 'map' pointers safely, knowing that
* [key, key + map->key_size) bytes are valid and were initialized on
* the stack of eBPF program.
* }
*
* Corresponding eBPF program may look like:
* BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), // after this insn R2 type is FRAME_PTR
* BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), // after this insn R2 type is PTR_TO_STACK
* BPF_LD_MAP_FD(BPF_REG_1, map_fd), // after this insn R1 type is CONST_PTR_TO_MAP
* BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
* here verifier looks at prototype of map_lookup_elem() and sees:
* .arg1_type == ARG_CONST_MAP_PTR and R1->type == CONST_PTR_TO_MAP, which is ok,
* Now verifier knows that this map has key of R1->map_ptr->key_size bytes
*
* Then .arg2_type == ARG_PTR_TO_MAP_KEY and R2->type == PTR_TO_STACK, ok so far,
* Now verifier checks that [R2, R2 + map's key_size) are within stack limits
* and were initialized prior to this call.
* If it's ok, then verifier allows this BPF_CALL insn and looks at
* .ret_type which is RET_PTR_TO_MAP_VALUE_OR_NULL, so it sets
* R0->type = PTR_TO_MAP_VALUE_OR_NULL which means bpf_map_lookup_elem() function
* returns ether pointer to map value or NULL.
*
* When type PTR_TO_MAP_VALUE_OR_NULL passes through 'if (reg != 0) goto +off'
* insn, the register holding that pointer in the true branch changes state to
* PTR_TO_MAP_VALUE and the same register changes state to CONST_IMM in the false
* branch. See check_cond_jmp_op().
*
* After the call R0 is set to return type of the function and registers R1-R5
* are set to NOT_INIT to indicate that they are no longer readable.
*
* The following reference types represent a potential reference to a kernel
* resource which, after first being allocated, must be checked and freed by
* the BPF program:
* - PTR_TO_SOCKET_OR_NULL, PTR_TO_SOCKET
*
* When the verifier sees a helper call return a reference type, it allocates a
* pointer id for the reference and stores it in the current function state.
* Similar to the way that PTR_TO_MAP_VALUE_OR_NULL is converted into
* PTR_TO_MAP_VALUE, PTR_TO_SOCKET_OR_NULL becomes PTR_TO_SOCKET when the type
* passes through a NULL-check conditional. For the branch wherein the state is
* changed to CONST_IMM, the verifier releases the reference.
*
* For each helper function that allocates a reference, such as
* bpf_sk_lookup_tcp(), there is a corresponding release function, such as
* bpf_sk_release(). When a reference type passes into the release function,
* the verifier also releases the reference. If any unchecked or unreleased
* reference remains at the end of the program, the verifier rejects it.
*/
/* verifier_state + insn_idx are pushed to stack when branch is encountered */
struct bpf_verifier_stack_elem {
/* verifer state is 'st'
* before processing instruction 'insn_idx'
* and after processing instruction 'prev_insn_idx'
*/
struct bpf_verifier_state st;
int insn_idx;
int prev_insn_idx;
struct bpf_verifier_stack_elem *next;
};
#define BPF_COMPLEXITY_LIMIT_INSNS 131072
#define BPF_COMPLEXITY_LIMIT_STACK 1024
#define BPF_COMPLEXITY_LIMIT_STATES 64
#define BPF_MAP_PTR_UNPRIV 1UL
#define BPF_MAP_PTR_POISON ((void *)((0xeB9FUL << 1) + \
POISON_POINTER_DELTA))
#define BPF_MAP_PTR(X) ((struct bpf_map *)((X) & ~BPF_MAP_PTR_UNPRIV))
static bool bpf_map_ptr_poisoned(const struct bpf_insn_aux_data *aux)
{
return BPF_MAP_PTR(aux->map_state) == BPF_MAP_PTR_POISON;
}
static bool bpf_map_ptr_unpriv(const struct bpf_insn_aux_data *aux)
{
return aux->map_state & BPF_MAP_PTR_UNPRIV;
}
static void bpf_map_ptr_store(struct bpf_insn_aux_data *aux,
const struct bpf_map *map, bool unpriv)
{
BUILD_BUG_ON((unsigned long)BPF_MAP_PTR_POISON & BPF_MAP_PTR_UNPRIV);
unpriv |= bpf_map_ptr_unpriv(aux);
aux->map_state = (unsigned long)map |
(unpriv ? BPF_MAP_PTR_UNPRIV : 0UL);
}
struct bpf_call_arg_meta {
struct bpf_map *map_ptr;
bool raw_mode;
bool pkt_access;
int regno;
int access_size;
s64 msize_smax_value;
u64 msize_umax_value;
int ref_obj_id;
int func_id;
};
static DEFINE_MUTEX(bpf_verifier_lock);
static const struct bpf_line_info *
find_linfo(const struct bpf_verifier_env *env, u32 insn_off)
{
const struct bpf_line_info *linfo;
const struct bpf_prog *prog;
u32 i, nr_linfo;
prog = env->prog;
nr_linfo = prog->aux->nr_linfo;
if (!nr_linfo || insn_off >= prog->len)
return NULL;
linfo = prog->aux->linfo;
for (i = 1; i < nr_linfo; i++)
if (insn_off < linfo[i].insn_off)
break;
return &linfo[i - 1];
}
void bpf_verifier_vlog(struct bpf_verifier_log *log, const char *fmt,
va_list args)
{
unsigned int n;
n = vscnprintf(log->kbuf, BPF_VERIFIER_TMP_LOG_SIZE, fmt, args);
WARN_ONCE(n >= BPF_VERIFIER_TMP_LOG_SIZE - 1,
"verifier log line truncated - local buffer too short\n");
n = min(log->len_total - log->len_used - 1, n);
log->kbuf[n] = '\0';
if (!copy_to_user(log->ubuf + log->len_used, log->kbuf, n + 1))
log->len_used += n;
else
log->ubuf = NULL;
}
/* log_level controls verbosity level of eBPF verifier.
* bpf_verifier_log_write() is used to dump the verification trace to the log,
* so the user can figure out what's wrong with the program
*/
__printf(2, 3) void bpf_verifier_log_write(struct bpf_verifier_env *env,
const char *fmt, ...)
{
va_list args;
if (!bpf_verifier_log_needed(&env->log))
return;
va_start(args, fmt);
bpf_verifier_vlog(&env->log, fmt, args);
va_end(args);
}
EXPORT_SYMBOL_GPL(bpf_verifier_log_write);
__printf(2, 3) static void verbose(void *private_data, const char *fmt, ...)
{
struct bpf_verifier_env *env = private_data;
va_list args;
if (!bpf_verifier_log_needed(&env->log))
return;
va_start(args, fmt);
bpf_verifier_vlog(&env->log, fmt, args);
va_end(args);
}
static const char *ltrim(const char *s)
{
while (isspace(*s))
s++;
return s;
}
__printf(3, 4) static void verbose_linfo(struct bpf_verifier_env *env,
u32 insn_off,
const char *prefix_fmt, ...)
{
const struct bpf_line_info *linfo;
if (!bpf_verifier_log_needed(&env->log))
return;
linfo = find_linfo(env, insn_off);
if (!linfo || linfo == env->prev_linfo)
return;
if (prefix_fmt) {
va_list args;
va_start(args, prefix_fmt);
bpf_verifier_vlog(&env->log, prefix_fmt, args);
va_end(args);
}
verbose(env, "%s\n",
ltrim(btf_name_by_offset(env->prog->aux->btf,
linfo->line_off)));
env->prev_linfo = linfo;
}
static bool type_is_pkt_pointer(enum bpf_reg_type type)
{
return type == PTR_TO_PACKET ||
type == PTR_TO_PACKET_META;
}
static bool type_is_sk_pointer(enum bpf_reg_type type)
{
return type == PTR_TO_SOCKET ||
type == PTR_TO_SOCK_COMMON ||
type == PTR_TO_TCP_SOCK;
}
static bool reg_type_may_be_null(enum bpf_reg_type type)
{
return type == PTR_TO_MAP_VALUE_OR_NULL ||
type == PTR_TO_SOCKET_OR_NULL ||
type == PTR_TO_SOCK_COMMON_OR_NULL ||
type == PTR_TO_TCP_SOCK_OR_NULL;
}
static bool reg_may_point_to_spin_lock(const struct bpf_reg_state *reg)
{
return reg->type == PTR_TO_MAP_VALUE &&
map_value_has_spin_lock(reg->map_ptr);
}
static bool reg_type_may_be_refcounted_or_null(enum bpf_reg_type type)
{
return type == PTR_TO_SOCKET ||
type == PTR_TO_SOCKET_OR_NULL ||
type == PTR_TO_TCP_SOCK ||
type == PTR_TO_TCP_SOCK_OR_NULL;
}
static bool arg_type_may_be_refcounted(enum bpf_arg_type type)
{
return type == ARG_PTR_TO_SOCK_COMMON;
}
/* Determine whether the function releases some resources allocated by another
* function call. The first reference type argument will be assumed to be
* released by release_reference().
*/
static bool is_release_function(enum bpf_func_id func_id)
{
return func_id == BPF_FUNC_sk_release;
}
static bool is_acquire_function(enum bpf_func_id func_id)
{
return func_id == BPF_FUNC_sk_lookup_tcp ||
func_id == BPF_FUNC_sk_lookup_udp;
}
static bool is_ptr_cast_function(enum bpf_func_id func_id)
{
return func_id == BPF_FUNC_tcp_sock ||
func_id == BPF_FUNC_sk_fullsock;
}
/* string representation of 'enum bpf_reg_type' */
static const char * const reg_type_str[] = {
[NOT_INIT] = "?",
[SCALAR_VALUE] = "inv",
[PTR_TO_CTX] = "ctx",
[CONST_PTR_TO_MAP] = "map_ptr",
[PTR_TO_MAP_VALUE] = "map_value",
[PTR_TO_MAP_VALUE_OR_NULL] = "map_value_or_null",
[PTR_TO_STACK] = "fp",
[PTR_TO_PACKET] = "pkt",
[PTR_TO_PACKET_META] = "pkt_meta",
[PTR_TO_PACKET_END] = "pkt_end",
[PTR_TO_FLOW_KEYS] = "flow_keys",
[PTR_TO_SOCKET] = "sock",
[PTR_TO_SOCKET_OR_NULL] = "sock_or_null",
[PTR_TO_SOCK_COMMON] = "sock_common",
[PTR_TO_SOCK_COMMON_OR_NULL] = "sock_common_or_null",
[PTR_TO_TCP_SOCK] = "tcp_sock",
[PTR_TO_TCP_SOCK_OR_NULL] = "tcp_sock_or_null",
};
static char slot_type_char[] = {
[STACK_INVALID] = '?',
[STACK_SPILL] = 'r',
[STACK_MISC] = 'm',
[STACK_ZERO] = '0',
};
static void print_liveness(struct bpf_verifier_env *env,
enum bpf_reg_liveness live)
{
if (live & (REG_LIVE_READ | REG_LIVE_WRITTEN | REG_LIVE_DONE))
verbose(env, "_");
if (live & REG_LIVE_READ)
verbose(env, "r");
if (live & REG_LIVE_WRITTEN)
verbose(env, "w");
if (live & REG_LIVE_DONE)
verbose(env, "D");
}
static struct bpf_func_state *func(struct bpf_verifier_env *env,
const struct bpf_reg_state *reg)
{
struct bpf_verifier_state *cur = env->cur_state;
return cur->frame[reg->frameno];
}
static void print_verifier_state(struct bpf_verifier_env *env,
const struct bpf_func_state *state)
{
const struct bpf_reg_state *reg;
enum bpf_reg_type t;
int i;
if (state->frameno)
verbose(env, " frame%d:", state->frameno);
for (i = 0; i < MAX_BPF_REG; i++) {
reg = &state->regs[i];
t = reg->type;
if (t == NOT_INIT)
continue;
verbose(env, " R%d", i);
print_liveness(env, reg->live);
verbose(env, "=%s", reg_type_str[t]);
if ((t == SCALAR_VALUE || t == PTR_TO_STACK) &&
tnum_is_const(reg->var_off)) {
/* reg->off should be 0 for SCALAR_VALUE */
verbose(env, "%lld", reg->var_off.value + reg->off);
if (t == PTR_TO_STACK)
verbose(env, ",call_%d", func(env, reg)->callsite);
} else {
verbose(env, "(id=%d", reg->id);
if (reg_type_may_be_refcounted_or_null(t))
verbose(env, ",ref_obj_id=%d", reg->ref_obj_id);
if (t != SCALAR_VALUE)
verbose(env, ",off=%d", reg->off);
if (type_is_pkt_pointer(t))
verbose(env, ",r=%d", reg->range);
else if (t == CONST_PTR_TO_MAP ||
t == PTR_TO_MAP_VALUE ||
t == PTR_TO_MAP_VALUE_OR_NULL)
verbose(env, ",ks=%d,vs=%d",
reg->map_ptr->key_size,
reg->map_ptr->value_size);
if (tnum_is_const(reg->var_off)) {
/* Typically an immediate SCALAR_VALUE, but
* could be a pointer whose offset is too big
* for reg->off
*/
verbose(env, ",imm=%llx", reg->var_off.value);
} else {
if (reg->smin_value != reg->umin_value &&
reg->smin_value != S64_MIN)
verbose(env, ",smin_value=%lld",
(long long)reg->smin_value);
if (reg->smax_value != reg->umax_value &&
reg->smax_value != S64_MAX)
verbose(env, ",smax_value=%lld",
(long long)reg->smax_value);
if (reg->umin_value != 0)
verbose(env, ",umin_value=%llu",
(unsigned long long)reg->umin_value);
if (reg->umax_value != U64_MAX)
verbose(env, ",umax_value=%llu",
(unsigned long long)reg->umax_value);
if (!tnum_is_unknown(reg->var_off)) {
char tn_buf[48];
tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
verbose(env, ",var_off=%s", tn_buf);
}
}
verbose(env, ")");
}
}
for (i = 0; i < state->allocated_stack / BPF_REG_SIZE; i++) {
char types_buf[BPF_REG_SIZE + 1];
bool valid = false;
int j;
for (j = 0; j < BPF_REG_SIZE; j++) {
if (state->stack[i].slot_type[j] != STACK_INVALID)
valid = true;
types_buf[j] = slot_type_char[
state->stack[i].slot_type[j]];
}
types_buf[BPF_REG_SIZE] = 0;
if (!valid)
continue;
verbose(env, " fp%d", (-i - 1) * BPF_REG_SIZE);
print_liveness(env, state->stack[i].spilled_ptr.live);
if (state->stack[i].slot_type[0] == STACK_SPILL)
verbose(env, "=%s",
reg_type_str[state->stack[i].spilled_ptr.type]);
else
verbose(env, "=%s", types_buf);
}
if (state->acquired_refs && state->refs[0].id) {
verbose(env, " refs=%d", state->refs[0].id);
for (i = 1; i < state->acquired_refs; i++)
if (state->refs[i].id)
verbose(env, ",%d", state->refs[i].id);
}
verbose(env, "\n");
}
#define COPY_STATE_FN(NAME, COUNT, FIELD, SIZE) \
static int copy_##NAME##_state(struct bpf_func_state *dst, \
const struct bpf_func_state *src) \
{ \
if (!src->FIELD) \
return 0; \
if (WARN_ON_ONCE(dst->COUNT < src->COUNT)) { \
/* internal bug, make state invalid to reject the program */ \
memset(dst, 0, sizeof(*dst)); \
return -EFAULT; \
} \
memcpy(dst->FIELD, src->FIELD, \
sizeof(*src->FIELD) * (src->COUNT / SIZE)); \
return 0; \
}
/* copy_reference_state() */
COPY_STATE_FN(reference, acquired_refs, refs, 1)
/* copy_stack_state() */
COPY_STATE_FN(stack, allocated_stack, stack, BPF_REG_SIZE)
#undef COPY_STATE_FN
#define REALLOC_STATE_FN(NAME, COUNT, FIELD, SIZE) \
static int realloc_##NAME##_state(struct bpf_func_state *state, int size, \
bool copy_old) \
{ \
u32 old_size = state->COUNT; \
struct bpf_##NAME##_state *new_##FIELD; \
int slot = size / SIZE; \
\
if (size <= old_size || !size) { \
if (copy_old) \
return 0; \
state->COUNT = slot * SIZE; \
if (!size && old_size) { \
kfree(state->FIELD); \
state->FIELD = NULL; \
} \
return 0; \
} \
new_##FIELD = kmalloc_array(slot, sizeof(struct bpf_##NAME##_state), \
GFP_KERNEL); \
if (!new_##FIELD) \
return -ENOMEM; \
if (copy_old) { \
if (state->FIELD) \
memcpy(new_##FIELD, state->FIELD, \
sizeof(*new_##FIELD) * (old_size / SIZE)); \
memset(new_##FIELD + old_size / SIZE, 0, \
sizeof(*new_##FIELD) * (size - old_size) / SIZE); \
} \
state->COUNT = slot * SIZE; \
kfree(state->FIELD); \
state->FIELD = new_##FIELD; \
return 0; \
}
/* realloc_reference_state() */
REALLOC_STATE_FN(reference, acquired_refs, refs, 1)
/* realloc_stack_state() */
REALLOC_STATE_FN(stack, allocated_stack, stack, BPF_REG_SIZE)
#undef REALLOC_STATE_FN
/* do_check() starts with zero-sized stack in struct bpf_verifier_state to
* make it consume minimal amount of memory. check_stack_write() access from
* the program calls into realloc_func_state() to grow the stack size.
* Note there is a non-zero 'parent' pointer inside bpf_verifier_state
* which realloc_stack_state() copies over. It points to previous
* bpf_verifier_state which is never reallocated.
*/
static int realloc_func_state(struct bpf_func_state *state, int stack_size,
int refs_size, bool copy_old)
{
int err = realloc_reference_state(state, refs_size, copy_old);
if (err)
return err;
return realloc_stack_state(state, stack_size, copy_old);
}
/* Acquire a pointer id from the env and update the state->refs to include
* this new pointer reference.
* On success, returns a valid pointer id to associate with the register
* On failure, returns a negative errno.
*/
static int acquire_reference_state(struct bpf_verifier_env *env, int insn_idx)
{
struct bpf_func_state *state = cur_func(env);
int new_ofs = state->acquired_refs;
int id, err;
err = realloc_reference_state(state, state->acquired_refs + 1, true);
if (err)
return err;
id = ++env->id_gen;
state->refs[new_ofs].id = id;
state->refs[new_ofs].insn_idx = insn_idx;
return id;
}
/* release function corresponding to acquire_reference_state(). Idempotent. */
static int release_reference_state(struct bpf_func_state *state, int ptr_id)
{
int i, last_idx;
last_idx = state->acquired_refs - 1;
for (i = 0; i < state->acquired_refs; i++) {
if (state->refs[i].id == ptr_id) {
if (last_idx && i != last_idx)
memcpy(&state->refs[i], &state->refs[last_idx],
sizeof(*state->refs));
memset(&state->refs[last_idx], 0, sizeof(*state->refs));
state->acquired_refs--;
return 0;
}
}
return -EINVAL;
}
static int transfer_reference_state(struct bpf_func_state *dst,
struct bpf_func_state *src)
{
int err = realloc_reference_state(dst, src->acquired_refs, false);
if (err)
return err;
err = copy_reference_state(dst, src);
if (err)
return err;
return 0;
}
static void free_func_state(struct bpf_func_state *state)
{
if (!state)
return;
kfree(state->refs);
kfree(state->stack);
kfree(state);
}
static void free_verifier_state(struct bpf_verifier_state *state,
bool free_self)
{
int i;
for (i = 0; i <= state->curframe; i++) {
free_func_state(state->frame[i]);
state->frame[i] = NULL;
}
if (free_self)
kfree(state);
}
/* copy verifier state from src to dst growing dst stack space
* when necessary to accommodate larger src stack
*/
static int copy_func_state(struct bpf_func_state *dst,
const struct bpf_func_state *src)
{
int err;
err = realloc_func_state(dst, src->allocated_stack, src->acquired_refs,
false);
if (err)
return err;
memcpy(dst, src, offsetof(struct bpf_func_state, acquired_refs));
err = copy_reference_state(dst, src);
if (err)
return err;
return copy_stack_state(dst, src);
}
static int copy_verifier_state(struct bpf_verifier_state *dst_state,
const struct bpf_verifier_state *src)
{
struct bpf_func_state *dst;
int i, err;
/* if dst has more stack frames then src frame, free them */
for (i = src->curframe + 1; i <= dst_state->curframe; i++) {
free_func_state(dst_state->frame[i]);
dst_state->frame[i] = NULL;
}
dst_state->speculative = src->speculative;
dst_state->curframe = src->curframe;
dst_state->active_spin_lock = src->active_spin_lock;
for (i = 0; i <= src->curframe; i++) {
dst = dst_state->frame[i];
if (!dst) {
dst = kzalloc(sizeof(*dst), GFP_KERNEL);
if (!dst)
return -ENOMEM;
dst_state->frame[i] = dst;
}
err = copy_func_state(dst, src->frame[i]);
if (err)
return err;
}
return 0;
}
static int pop_stack(struct bpf_verifier_env *env, int *prev_insn_idx,
int *insn_idx)
{
struct bpf_verifier_state *cur = env->cur_state;
struct bpf_verifier_stack_elem *elem, *head = env->head;
int err;
if (env->head == NULL)
return -ENOENT;
if (cur) {
err = copy_verifier_state(cur, &head->st);
if (err)
return err;
}
if (insn_idx)
*insn_idx = head->insn_idx;
if (prev_insn_idx)
*prev_insn_idx = head->prev_insn_idx;
elem = head->next;
free_verifier_state(&head->st, false);
kfree(head);
env->head = elem;
env->stack_size--;
return 0;
}
static struct bpf_verifier_state *push_stack(struct bpf_verifier_env *env,
int insn_idx, int prev_insn_idx,
bool speculative)
{
struct bpf_verifier_state *cur = env->cur_state;
struct bpf_verifier_stack_elem *elem;
int err;
elem = kzalloc(sizeof(struct bpf_verifier_stack_elem), GFP_KERNEL);
if (!elem)
goto err;
elem->insn_idx = insn_idx;
elem->prev_insn_idx = prev_insn_idx;
elem->next = env->head;
env->head = elem;
env->stack_size++;
err = copy_verifier_state(&elem->st, cur);
if (err)
goto err;
elem->st.speculative |= speculative;
if (env->stack_size > BPF_COMPLEXITY_LIMIT_STACK) {
verbose(env, "BPF program is too complex\n");
goto err;
}
return &elem->st;
err:
free_verifier_state(env->cur_state, true);
env->cur_state = NULL;
/* pop all elements and return */
while (!pop_stack(env, NULL, NULL));
return NULL;
}
#define CALLER_SAVED_REGS 6
static const int caller_saved[CALLER_SAVED_REGS] = {
BPF_REG_0, BPF_REG_1, BPF_REG_2, BPF_REG_3, BPF_REG_4, BPF_REG_5
};
static void __mark_reg_not_init(struct bpf_reg_state *reg);
/* Mark the unknown part of a register (variable offset or scalar value) as
* known to have the value @imm.
*/
static void __mark_reg_known(struct bpf_reg_state *reg, u64 imm)
{
/* Clear id, off, and union(map_ptr, range) */
memset(((u8 *)reg) + sizeof(reg->type), 0,
offsetof(struct bpf_reg_state, var_off) - sizeof(reg->type));
reg->var_off = tnum_const(imm);
reg->smin_value = (s64)imm;
reg->smax_value = (s64)imm;
reg->umin_value = imm;
reg->umax_value = imm;
}
/* Mark the 'variable offset' part of a register as zero. This should be
* used only on registers holding a pointer type.
*/
static void __mark_reg_known_zero(struct bpf_reg_state *reg)
{
__mark_reg_known(reg, 0);
}
static void __mark_reg_const_zero(struct bpf_reg_state *reg)
{
__mark_reg_known(reg, 0);
reg->type = SCALAR_VALUE;
}
static void mark_reg_known_zero(struct bpf_verifier_env *env,
struct bpf_reg_state *regs, u32 regno)
{
if (WARN_ON(regno >= MAX_BPF_REG)) {
verbose(env, "mark_reg_known_zero(regs, %u)\n", regno);
/* Something bad happened, let's kill all regs */
for (regno = 0; regno < MAX_BPF_REG; regno++)
__mark_reg_not_init(regs + regno);
return;
}
__mark_reg_known_zero(regs + regno);
}
static bool reg_is_pkt_pointer(const struct bpf_reg_state *reg)
{
return type_is_pkt_pointer(reg->type);
}
static bool reg_is_pkt_pointer_any(const struct bpf_reg_state *reg)
{
return reg_is_pkt_pointer(reg) ||
reg->type == PTR_TO_PACKET_END;
}
/* Unmodified PTR_TO_PACKET[_META,_END] register from ctx access. */
static bool reg_is_init_pkt_pointer(const struct bpf_reg_state *reg,
enum bpf_reg_type which)
{
/* The register can already have a range from prior markings.
* This is fine as long as it hasn't been advanced from its
* origin.
*/
return reg->type == which &&
reg->id == 0 &&
reg->off == 0 &&
tnum_equals_const(reg->var_off, 0);
}
/* Attempts to improve min/max values based on var_off information */
static void __update_reg_bounds(struct bpf_reg_state *reg)
{
/* min signed is max(sign bit) | min(other bits) */
reg->smin_value = max_t(s64, reg->smin_value,
reg->var_off.value | (reg->var_off.mask & S64_MIN));
/* max signed is min(sign bit) | max(other bits) */
reg->smax_value = min_t(s64, reg->smax_value,
reg->var_off.value | (reg->var_off.mask & S64_MAX));
reg->umin_value = max(reg->umin_value, reg->var_off.value);
reg->umax_value = min(reg->umax_value,
reg->var_off.value | reg->var_off.mask);
}
/* Uses signed min/max values to inform unsigned, and vice-versa */
static void __reg_deduce_bounds(struct bpf_reg_state *reg)
{
/* Learn sign from signed bounds.
* If we cannot cross the sign boundary, then signed and unsigned bounds
* are the same, so combine. This works even in the negative case, e.g.
* -3 s<= x s<= -1 implies 0xf...fd u<= x u<= 0xf...ff.
*/
if (reg->smin_value >= 0 || reg->smax_value < 0) {
reg->smin_value = reg->umin_value = max_t(u64, reg->smin_value,
reg->umin_value);
reg->smax_value = reg->umax_value = min_t(u64, reg->smax_value,
reg->umax_value);
return;
}
/* Learn sign from unsigned bounds. Signed bounds cross the sign
* boundary, so we must be careful.
*/
if ((s64)reg->umax_value >= 0) {
/* Positive. We can't learn anything from the smin, but smax
* is positive, hence safe.
*/
reg->smin_value = reg->umin_value;
reg->smax_value = reg->umax_value = min_t(u64, reg->smax_value,
reg->umax_value);
} else if ((s64)reg->umin_value < 0) {
/* Negative. We can't learn anything from the smax, but smin
* is negative, hence safe.
*/
reg->smin_value = reg->umin_value = max_t(u64, reg->smin_value,
reg->umin_value);
reg->smax_value = reg->umax_value;
}
}
/* Attempts to improve var_off based on unsigned min/max information */
static void __reg_bound_offset(struct bpf_reg_state *reg)
{
reg->var_off = tnum_intersect(reg->var_off,
tnum_range(reg->umin_value,
reg->umax_value));
}
/* Reset the min/max bounds of a register */
static void __mark_reg_unbounded(struct bpf_reg_state *reg)
{
reg->smin_value = S64_MIN;
reg->smax_value = S64_MAX;
reg->umin_value = 0;
reg->umax_value = U64_MAX;
}
/* Mark a register as having a completely unknown (scalar) value. */
static void __mark_reg_unknown(struct bpf_reg_state *reg)
{
/*
* Clear type, id, off, and union(map_ptr, range) and
* padding between 'type' and union
*/
memset(reg, 0, offsetof(struct bpf_reg_state, var_off));
reg->type = SCALAR_VALUE;
reg->var_off = tnum_unknown;
reg->frameno = 0;
__mark_reg_unbounded(reg);
}
static void mark_reg_unknown(struct bpf_verifier_env *env,
struct bpf_reg_state *regs, u32 regno)
{
if (WARN_ON(regno >= MAX_BPF_REG)) {
verbose(env, "mark_reg_unknown(regs, %u)\n", regno);
/* Something bad happened, let's kill all regs except FP */
for (regno = 0; regno < BPF_REG_FP; regno++)
__mark_reg_not_init(regs + regno);
return;
}
__mark_reg_unknown(regs + regno);
}
static void __mark_reg_not_init(struct bpf_reg_state *reg)
{
__mark_reg_unknown(reg);
reg->type = NOT_INIT;
}
static void mark_reg_not_init(struct bpf_verifier_env *env,
struct bpf_reg_state *regs, u32 regno)
{
if (WARN_ON(regno >= MAX_BPF_REG)) {
verbose(env, "mark_reg_not_init(regs, %u)\n", regno);
/* Something bad happened, let's kill all regs except FP */
for (regno = 0; regno < BPF_REG_FP; regno++)
__mark_reg_not_init(regs + regno);
return;
}
__mark_reg_not_init(regs + regno);
}
static void init_reg_state(struct bpf_verifier_env *env,
struct bpf_func_state *state)
{
struct bpf_reg_state *regs = state->regs;
int i;
for (i = 0; i < MAX_BPF_REG; i++) {
mark_reg_not_init(env, regs, i);
regs[i].live = REG_LIVE_NONE;
regs[i].parent = NULL;
}
/* frame pointer */
regs[BPF_REG_FP].type = PTR_TO_STACK;
mark_reg_known_zero(env, regs, BPF_REG_FP);
regs[BPF_REG_FP].frameno = state->frameno;
/* 1st arg to a function */
regs[BPF_REG_1].type = PTR_TO_CTX;
mark_reg_known_zero(env, regs, BPF_REG_1);
}
#define BPF_MAIN_FUNC (-1)
static void init_func_state(struct bpf_verifier_env *env,
struct bpf_func_state *state,
int callsite, int frameno, int subprogno)
{
state->callsite = callsite;
state->frameno = frameno;
state->subprogno = subprogno;
init_reg_state(env, state);
}
enum reg_arg_type {
SRC_OP, /* register is used as source operand */
DST_OP, /* register is used as destination operand */
DST_OP_NO_MARK /* same as above, check only, don't mark */
};
static int cmp_subprogs(const void *a, const void *b)
{
return ((struct bpf_subprog_info *)a)->start -
((struct bpf_subprog_info *)b)->start;
}
static int find_subprog(struct bpf_verifier_env *env, int off)
{
struct bpf_subprog_info *p;
p = bsearch(&off, env->subprog_info, env->subprog_cnt,
sizeof(env->subprog_info[0]), cmp_subprogs);
if (!p)
return -ENOENT;
return p - env->subprog_info;
}
static int add_subprog(struct bpf_verifier_env *env, int off)
{
int insn_cnt = env->prog->len;
int ret;
if (off >= insn_cnt || off < 0) {
verbose(env, "call to invalid destination\n");
return -EINVAL;
}
ret = find_subprog(env, off);
if (ret >= 0)
return 0;
if (env->subprog_cnt >= BPF_MAX_SUBPROGS) {
verbose(env, "too many subprograms\n");
return -E2BIG;
}
env->subprog_info[env->subprog_cnt++].start = off;
sort(env->subprog_info, env->subprog_cnt,
sizeof(env->subprog_info[0]), cmp_subprogs, NULL);
return 0;
}
static int check_subprogs(struct bpf_verifier_env *env)
{
int i, ret, subprog_start, subprog_end, off, cur_subprog = 0;
struct bpf_subprog_info *subprog = env->subprog_info;
struct bpf_insn *insn = env->prog->insnsi;
int insn_cnt = env->prog->len;
/* Add entry function. */
ret = add_subprog(env, 0);
if (ret < 0)
return ret;
/* determine subprog starts. The end is one before the next starts */
for (i = 0; i < insn_cnt; i++) {
if (insn[i].code != (BPF_JMP | BPF_CALL))
continue;
if (insn[i].src_reg != BPF_PSEUDO_CALL)
continue;
if (!env->allow_ptr_leaks) {
verbose(env, "function calls to other bpf functions are allowed for root only\n");
return -EPERM;
}
ret = add_subprog(env, i + insn[i].imm + 1);
if (ret < 0)
return ret;
}
/* Add a fake 'exit' subprog which could simplify subprog iteration
* logic. 'subprog_cnt' should not be increased.
*/
subprog[env->subprog_cnt].start = insn_cnt;
if (env->log.level > 1)
for (i = 0; i < env->subprog_cnt; i++)
verbose(env, "func#%d @%d\n", i, subprog[i].start);
/* now check that all jumps are within the same subprog */
subprog_start = subprog[cur_subprog].start;
subprog_end = subprog[cur_subprog + 1].start;
for (i = 0; i < insn_cnt; i++) {
u8 code = insn[i].code;
if (BPF_CLASS(code) != BPF_JMP && BPF_CLASS(code) != BPF_JMP32)
goto next;
if (BPF_OP(code) == BPF_EXIT || BPF_OP(code) == BPF_CALL)
goto next;
off = i + insn[i].off + 1;
if (off < subprog_start || off >= subprog_end) {
verbose(env, "jump out of range from insn %d to %d\n", i, off);
return -EINVAL;
}
next:
if (i == subprog_end - 1) {
/* to avoid fall-through from one subprog into another
* the last insn of the subprog should be either exit
* or unconditional jump back
*/
if (code != (BPF_JMP | BPF_EXIT) &&
code != (BPF_JMP | BPF_JA)) {
verbose(env, "last insn is not an exit or jmp\n");
return -EINVAL;
}
subprog_start = subprog_end;
cur_subprog++;
if (cur_subprog < env->subprog_cnt)
subprog_end = subprog[cur_subprog + 1].start;
}
}
return 0;
}
/* Parentage chain of this register (or stack slot) should take care of all
* issues like callee-saved registers, stack slot allocation time, etc.
*/
static int mark_reg_read(struct bpf_verifier_env *env,
const struct bpf_reg_state *state,
struct bpf_reg_state *parent)
{
bool writes = parent == state->parent; /* Observe write marks */
while (parent) {
/* if read wasn't screened by an earlier write ... */
if (writes && state->live & REG_LIVE_WRITTEN)
break;
if (parent->live & REG_LIVE_DONE) {
verbose(env, "verifier BUG type %s var_off %lld off %d\n",
reg_type_str[parent->type],
parent->var_off.value, parent->off);
return -EFAULT;
}
/* ... then we depend on parent's value */
parent->live |= REG_LIVE_READ;
state = parent;
parent = state->parent;
writes = true;
}
return 0;
}
static int check_reg_arg(struct bpf_verifier_env *env, u32 regno,
enum reg_arg_type t)
{
struct bpf_verifier_state *vstate = env->cur_state;
struct bpf_func_state *state = vstate->frame[vstate->curframe];
struct bpf_reg_state *regs = state->regs;
if (regno >= MAX_BPF_REG) {
verbose(env, "R%d is invalid\n", regno);
return -EINVAL;
}
if (t == SRC_OP) {
/* check whether register used as source operand can be read */
if (regs[regno].type == NOT_INIT) {
verbose(env, "R%d !read_ok\n", regno);
return -EACCES;
}
/* We don't need to worry about FP liveness because it's read-only */
if (regno != BPF_REG_FP)
return mark_reg_read(env, &regs[regno],
regs[regno].parent);
} else {
/* check whether register used as dest operand can be written to */
if (regno == BPF_REG_FP) {
verbose(env, "frame pointer is read only\n");
return -EACCES;
}
regs[regno].live |= REG_LIVE_WRITTEN;
if (t == DST_OP)
mark_reg_unknown(env, regs, regno);
}
return 0;
}
static bool is_spillable_regtype(enum bpf_reg_type type)
{
switch (type) {
case PTR_TO_MAP_VALUE:
case PTR_TO_MAP_VALUE_OR_NULL:
case PTR_TO_STACK:
case PTR_TO_CTX:
case PTR_TO_PACKET:
case PTR_TO_PACKET_META:
case PTR_TO_PACKET_END:
case PTR_TO_FLOW_KEYS:
case CONST_PTR_TO_MAP:
case PTR_TO_SOCKET:
case PTR_TO_SOCKET_OR_NULL:
case PTR_TO_SOCK_COMMON:
case PTR_TO_SOCK_COMMON_OR_NULL:
case PTR_TO_TCP_SOCK:
case PTR_TO_TCP_SOCK_OR_NULL:
return true;
default:
return false;
}
}
/* Does this register contain a constant zero? */
static bool register_is_null(struct bpf_reg_state *reg)
{
return reg->type == SCALAR_VALUE && tnum_equals_const(reg->var_off, 0);
}
/* check_stack_read/write functions track spill/fill of registers,
* stack boundary and alignment are checked in check_mem_access()
*/
static int check_stack_write(struct bpf_verifier_env *env,
struct bpf_func_state *state, /* func where register points to */
int off, int size, int value_regno, int insn_idx)
{
struct bpf_func_state *cur; /* state of the current function */
int i, slot = -off - 1, spi = slot / BPF_REG_SIZE, err;
enum bpf_reg_type type;
err = realloc_func_state(state, round_up(slot + 1, BPF_REG_SIZE),
state->acquired_refs, true);
if (err)
return err;
/* caller checked that off % size == 0 and -MAX_BPF_STACK <= off < 0,
* so it's aligned access and [off, off + size) are within stack limits
*/
if (!env->allow_ptr_leaks &&
state->stack[spi].slot_type[0] == STACK_SPILL &&
size != BPF_REG_SIZE) {
verbose(env, "attempt to corrupt spilled pointer on stack\n");
return -EACCES;
}
cur = env->cur_state->frame[env->cur_state->curframe];
if (value_regno >= 0 &&
is_spillable_regtype((type = cur->regs[value_regno].type))) {
/* register containing pointer is being spilled into stack */
if (size != BPF_REG_SIZE) {
verbose(env, "invalid size of register spill\n");
return -EACCES;
}
if (state != cur && type == PTR_TO_STACK) {
verbose(env, "cannot spill pointers to stack into stack frame of the caller\n");
return -EINVAL;
}
/* save register state */
state->stack[spi].spilled_ptr = cur->regs[value_regno];
state->stack[spi].spilled_ptr.live |= REG_LIVE_WRITTEN;
for (i = 0; i < BPF_REG_SIZE; i++) {
if (state->stack[spi].slot_type[i] == STACK_MISC &&
!env->allow_ptr_leaks) {
int *poff = &env->insn_aux_data[insn_idx].sanitize_stack_off;
int soff = (-spi - 1) * BPF_REG_SIZE;
/* detected reuse of integer stack slot with a pointer
* which means either llvm is reusing stack slot or
* an attacker is trying to exploit CVE-2018-3639
* (speculative store bypass)
* Have to sanitize that slot with preemptive
* store of zero.
*/
if (*poff && *poff != soff) {
/* disallow programs where single insn stores
* into two different stack slots, since verifier
* cannot sanitize them
*/
verbose(env,
"insn %d cannot access two stack slots fp%d and fp%d",
insn_idx, *poff, soff);
return -EINVAL;
}
*poff = soff;
}
state->stack[spi].slot_type[i] = STACK_SPILL;
}
} else {
u8 type = STACK_MISC;
/* regular write of data into stack destroys any spilled ptr */
state->stack[spi].spilled_ptr.type = NOT_INIT;
/* Mark slots as STACK_MISC if they belonged to spilled ptr. */
if (state->stack[spi].slot_type[0] == STACK_SPILL)
for (i = 0; i < BPF_REG_SIZE; i++)
state->stack[spi].slot_type[i] = STACK_MISC;
/* only mark the slot as written if all 8 bytes were written
* otherwise read propagation may incorrectly stop too soon
* when stack slots are partially written.
* This heuristic means that read propagation will be
* conservative, since it will add reg_live_read marks
* to stack slots all the way to first state when programs
* writes+reads less than 8 bytes
*/
if (size == BPF_REG_SIZE)
state->stack[spi].spilled_ptr.live |= REG_LIVE_WRITTEN;
/* when we zero initialize stack slots mark them as such */
if (value_regno >= 0 &&
register_is_null(&cur->regs[value_regno]))
type = STACK_ZERO;
/* Mark slots affected by this stack write. */
for (i = 0; i < size; i++)
state->stack[spi].slot_type[(slot - i) % BPF_REG_SIZE] =
type;
}
return 0;
}
static int check_stack_read(struct bpf_verifier_env *env,
struct bpf_func_state *reg_state /* func where register points to */,
int off, int size, int value_regno)
{
struct bpf_verifier_state *vstate = env->cur_state;
struct bpf_func_state *state = vstate->frame[vstate->curframe];
int i, slot = -off - 1, spi = slot / BPF_REG_SIZE;
u8 *stype;
if (reg_state->allocated_stack <= slot) {
verbose(env, "invalid read from stack off %d+0 size %d\n",
off, size);
return -EACCES;
}
stype = reg_state->stack[spi].slot_type;
if (stype[0] == STACK_SPILL) {
if (size != BPF_REG_SIZE) {
verbose(env, "invalid size of register spill\n");
return -EACCES;
}
for (i = 1; i < BPF_REG_SIZE; i++) {
if (stype[(slot - i) % BPF_REG_SIZE] != STACK_SPILL) {
verbose(env, "corrupted spill memory\n");
return -EACCES;
}
}
if (value_regno >= 0) {
/* restore register state from stack */
state->regs[value_regno] = reg_state->stack[spi].spilled_ptr;
/* mark reg as written since spilled pointer state likely
* has its liveness marks cleared by is_state_visited()
* which resets stack/reg liveness for state transitions
*/
state->regs[value_regno].live |= REG_LIVE_WRITTEN;
}
mark_reg_read(env, &reg_state->stack[spi].spilled_ptr,
reg_state->stack[spi].spilled_ptr.parent);
return 0;
} else {
int zeros = 0;
for (i = 0; i < size; i++) {
if (stype[(slot - i) % BPF_REG_SIZE] == STACK_MISC)
continue;
if (stype[(slot - i) % BPF_REG_SIZE] == STACK_ZERO) {
zeros++;
continue;
}
verbose(env, "invalid read from stack off %d+%d size %d\n",
off, i, size);
return -EACCES;
}
mark_reg_read(env, &reg_state->stack[spi].spilled_ptr,
reg_state->stack[spi].spilled_ptr.parent);
if (value_regno >= 0) {
if (zeros == size) {
/* any size read into register is zero extended,
* so the whole register == const_zero
*/
__mark_reg_const_zero(&state->regs[value_regno]);
} else {
/* have read misc data from the stack */
mark_reg_unknown(env, state->regs, value_regno);
}
state->regs[value_regno].live |= REG_LIVE_WRITTEN;
}
return 0;
}
}
static int check_stack_access(struct bpf_verifier_env *env,
const struct bpf_reg_state *reg,
int off, int size)
{
/* Stack accesses must be at a fixed offset, so that we
* can determine what type of data were returned. See
* check_stack_read().
*/
if (!tnum_is_const(reg->var_off)) {
char tn_buf[48];
tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
verbose(env, "variable stack access var_off=%s off=%d size=%d",
tn_buf, off, size);
return -EACCES;
}
if (off >= 0 || off < -MAX_BPF_STACK) {
verbose(env, "invalid stack off=%d size=%d\n", off, size);
return -EACCES;
}
return 0;
}
/* check read/write into map element returned by bpf_map_lookup_elem() */
static int __check_map_access(struct bpf_verifier_env *env, u32 regno, int off,
int size, bool zero_size_allowed)
{
struct bpf_reg_state *regs = cur_regs(env);
struct bpf_map *map = regs[regno].map_ptr;
if (off < 0 || size < 0 || (size == 0 && !zero_size_allowed) ||
off + size > map->value_size) {
verbose(env, "invalid access to map value, value_size=%d off=%d size=%d\n",
map->value_size, off, size);
return -EACCES;
}
return 0;
}
/* check read/write into a map element with possible variable offset */
static int check_map_access(struct bpf_verifier_env *env, u32 regno,
int off, int size, bool zero_size_allowed)
{
struct bpf_verifier_state *vstate = env->cur_state;
struct bpf_func_state *state = vstate->frame[vstate->curframe];
struct bpf_reg_state *reg = &state->regs[regno];
int err;
/* We may have adjusted the register to this map value, so we
* need to try adding each of min_value and max_value to off
* to make sure our theoretical access will be safe.
*/
if (env->log.level)
print_verifier_state(env, state);
/* The minimum value is only important with signed
* comparisons where we can't assume the floor of a
* value is 0. If we are using signed variables for our
* index'es we need to make sure that whatever we use
* will have a set floor within our range.
*/
if (reg->smin_value < 0 &&
(reg->smin_value == S64_MIN ||
(off + reg->smin_value != (s64)(s32)(off + reg->smin_value)) ||
reg->smin_value + off < 0)) {
verbose(env, "R%d min value is negative, either use unsigned index or do a if (index >=0) check.\n",
regno);
return -EACCES;
}
err = __check_map_access(env, regno, reg->smin_value + off, size,
zero_size_allowed);
if (err) {
verbose(env, "R%d min value is outside of the array range\n",
regno);
return err;
}
/* If we haven't set a max value then we need to bail since we can't be
* sure we won't do bad things.
* If reg->umax_value + off could overflow, treat that as unbounded too.
*/
if (reg->umax_value >= BPF_MAX_VAR_OFF) {
verbose(env, "R%d unbounded memory access, make sure to bounds check any array access into a map\n",
regno);
return -EACCES;
}
err = __check_map_access(env, regno, reg->umax_value + off, size,
zero_size_allowed);
if (err)
verbose(env, "R%d max value is outside of the array range\n",
regno);
if (map_value_has_spin_lock(reg->map_ptr)) {
u32 lock = reg->map_ptr->spin_lock_off;
/* if any part of struct bpf_spin_lock can be touched by
* load/store reject this program.
* To check that [x1, x2) overlaps with [y1, y2)
* it is sufficient to check x1 < y2 && y1 < x2.
*/
if (reg->smin_value + off < lock + sizeof(struct bpf_spin_lock) &&
lock < reg->umax_value + off + size) {
verbose(env, "bpf_spin_lock cannot be accessed directly by load/store\n");
return -EACCES;
}
}
return err;
}
#define MAX_PACKET_OFF 0xffff
static bool may_access_direct_pkt_data(struct bpf_verifier_env *env,
const struct bpf_call_arg_meta *meta,
enum bpf_access_type t)
{
switch (env->prog->type) {
/* Program types only with direct read access go here! */
case BPF_PROG_TYPE_LWT_IN:
case BPF_PROG_TYPE_LWT_OUT:
case BPF_PROG_TYPE_LWT_SEG6LOCAL:
case BPF_PROG_TYPE_SK_REUSEPORT:
case BPF_PROG_TYPE_FLOW_DISSECTOR:
case BPF_PROG_TYPE_CGROUP_SKB:
if (t == BPF_WRITE)
return false;
/* fallthrough */
/* Program types with direct read + write access go here! */
case BPF_PROG_TYPE_SCHED_CLS:
case BPF_PROG_TYPE_SCHED_ACT:
case BPF_PROG_TYPE_XDP:
case BPF_PROG_TYPE_LWT_XMIT:
case BPF_PROG_TYPE_SK_SKB:
case BPF_PROG_TYPE_SK_MSG:
if (meta)
return meta->pkt_access;
env->seen_direct_write = true;
return true;
default:
return false;
}
}
static int __check_packet_access(struct bpf_verifier_env *env, u32 regno,
int off, int size, bool zero_size_allowed)
{
struct bpf_reg_state *regs = cur_regs(env);
struct bpf_reg_state *reg = &regs[regno];
if (off < 0 || size < 0 || (size == 0 && !zero_size_allowed) ||
(u64)off + size > reg->range) {
verbose(env, "invalid access to packet, off=%d size=%d, R%d(id=%d,off=%d,r=%d)\n",
off, size, regno, reg->id, reg->off, reg->range);
return -EACCES;
}
return 0;
}
static int check_packet_access(struct bpf_verifier_env *env, u32 regno, int off,
int size, bool zero_size_allowed)
{
struct bpf_reg_state *regs = cur_regs(env);
struct bpf_reg_state *reg = &regs[regno];
int err;
/* We may have added a variable offset to the packet pointer; but any
* reg->range we have comes after that. We are only checking the fixed
* offset.
*/
/* We don't allow negative numbers, because we aren't tracking enough
* detail to prove they're safe.
*/
if (reg->smin_value < 0) {
verbose(env, "R%d min value is negative, either use unsigned index or do a if (index >=0) check.\n",
regno);
return -EACCES;
}
err = __check_packet_access(env, regno, off, size, zero_size_allowed);
if (err) {
verbose(env, "R%d offset is outside of the packet\n", regno);
return err;
}
/* __check_packet_access has made sure "off + size - 1" is within u16.
* reg->umax_value can't be bigger than MAX_PACKET_OFF which is 0xffff,
* otherwise find_good_pkt_pointers would have refused to set range info
* that __check_packet_access would have rejected this pkt access.
* Therefore, "off + reg->umax_value + size - 1" won't overflow u32.
*/
env->prog->aux->max_pkt_offset =
max_t(u32, env->prog->aux->max_pkt_offset,
off + reg->umax_value + size - 1);
return err;
}
/* check access to 'struct bpf_context' fields. Supports fixed offsets only */
static int check_ctx_access(struct bpf_verifier_env *env, int insn_idx, int off, int size,
enum bpf_access_type t, enum bpf_reg_type *reg_type)
{
struct bpf_insn_access_aux info = {
.reg_type = *reg_type,
};
if (env->ops->is_valid_access &&
env->ops->is_valid_access(off, size, t, env->prog, &info)) {
/* A non zero info.ctx_field_size indicates that this field is a
* candidate for later verifier transformation to load the whole
* field and then apply a mask when accessed with a narrower
* access than actual ctx access size. A zero info.ctx_field_size
* will only allow for whole field access and rejects any other
* type of narrower access.
*/
*reg_type = info.reg_type;
env->insn_aux_data[insn_idx].ctx_field_size = info.ctx_field_size;
/* remember the offset of last byte accessed in ctx */
if (env->prog->aux->max_ctx_offset < off + size)
env->prog->aux->max_ctx_offset = off + size;
return 0;
}
verbose(env, "invalid bpf_context access off=%d size=%d\n", off, size);
return -EACCES;
}
static int check_flow_keys_access(struct bpf_verifier_env *env, int off,
int size)
{
if (size < 0 || off < 0 ||
(u64)off + size > sizeof(struct bpf_flow_keys)) {
verbose(env, "invalid access to flow keys off=%d size=%d\n",
off, size);
return -EACCES;
}
return 0;
}
static int check_sock_access(struct bpf_verifier_env *env, int insn_idx,
u32 regno, int off, int size,
enum bpf_access_type t)
{
struct bpf_reg_state *regs = cur_regs(env);
struct bpf_reg_state *reg = &regs[regno];
struct bpf_insn_access_aux info = {};
bool valid;
if (reg->smin_value < 0) {
verbose(env, "R%d min value is negative, either use unsigned index or do a if (index >=0) check.\n",
regno);
return -EACCES;
}
switch (reg->type) {
case PTR_TO_SOCK_COMMON:
valid = bpf_sock_common_is_valid_access(off, size, t, &info);
break;
case PTR_TO_SOCKET:
valid = bpf_sock_is_valid_access(off, size, t, &info);
break;
case PTR_TO_TCP_SOCK:
valid = bpf_tcp_sock_is_valid_access(off, size, t, &info);
break;
default:
valid = false;
}
if (valid) {
env->insn_aux_data[insn_idx].ctx_field_size =
info.ctx_field_size;
return 0;
}
verbose(env, "R%d invalid %s access off=%d size=%d\n",
regno, reg_type_str[reg->type], off, size);
return -EACCES;
}
static bool __is_pointer_value(bool allow_ptr_leaks,
const struct bpf_reg_state *reg)
{
if (allow_ptr_leaks)
return false;
return reg->type != SCALAR_VALUE;
}
static struct bpf_reg_state *reg_state(struct bpf_verifier_env *env, int regno)
{
return cur_regs(env) + regno;
}
static bool is_pointer_value(struct bpf_verifier_env *env, int regno)
{
return __is_pointer_value(env->allow_ptr_leaks, reg_state(env, regno));
}
static bool is_ctx_reg(struct bpf_verifier_env *env, int regno)
{
const struct bpf_reg_state *reg = reg_state(env, regno);
return reg->type == PTR_TO_CTX;
}
static bool is_sk_reg(struct bpf_verifier_env *env, int regno)
{
const struct bpf_reg_state *reg = reg_state(env, regno);
return type_is_sk_pointer(reg->type);
}
static bool is_pkt_reg(struct bpf_verifier_env *env, int regno)
{
const struct bpf_reg_state *reg = reg_state(env, regno);
return type_is_pkt_pointer(reg->type);
}
static bool is_flow_key_reg(struct bpf_verifier_env *env, int regno)
{
const struct bpf_reg_state *reg = reg_state(env, regno);
/* Separate to is_ctx_reg() since we still want to allow BPF_ST here. */
return reg->type == PTR_TO_FLOW_KEYS;
}
static int check_pkt_ptr_alignment(struct bpf_verifier_env *env,
const struct bpf_reg_state *reg,
int off, int size, bool strict)
{
struct tnum reg_off;
int ip_align;
/* Byte size accesses are always allowed. */
if (!strict || size == 1)
return 0;
/* For platforms that do not have a Kconfig enabling
* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS the value of
* NET_IP_ALIGN is universally set to '2'. And on platforms
* that do set CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS, we get
* to this code only in strict mode where we want to emulate
* the NET_IP_ALIGN==2 checking. Therefore use an
* unconditional IP align value of '2'.
*/
ip_align = 2;
reg_off = tnum_add(reg->var_off, tnum_const(ip_align + reg->off + off));
if (!tnum_is_aligned(reg_off, size)) {
char tn_buf[48];
tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
verbose(env,
"misaligned packet access off %d+%s+%d+%d size %d\n",
ip_align, tn_buf, reg->off, off, size);
return -EACCES;
}
return 0;
}
static int check_generic_ptr_alignment(struct bpf_verifier_env *env,
const struct bpf_reg_state *reg,
const char *pointer_desc,
int off, int size, bool strict)
{
struct tnum reg_off;
/* Byte size accesses are always allowed. */
if (!strict || size == 1)
return 0;
reg_off = tnum_add(reg->var_off, tnum_const(reg->off + off));
if (!tnum_is_aligned(reg_off, size)) {
char tn_buf[48];
tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
verbose(env, "misaligned %saccess off %s+%d+%d size %d\n",
pointer_desc, tn_buf, reg->off, off, size);
return -EACCES;
}
return 0;
}
static int check_ptr_alignment(struct bpf_verifier_env *env,
const struct bpf_reg_state *reg, int off,
int size, bool strict_alignment_once)
{
bool strict = env->strict_alignment || strict_alignment_once;
const char *pointer_desc = "";
switch (reg->type) {
case PTR_TO_PACKET:
case PTR_TO_PACKET_META:
/* Special case, because of NET_IP_ALIGN. Given metadata sits
* right in front, treat it the very same way.
*/
return check_pkt_ptr_alignment(env, reg, off, size, strict);
case PTR_TO_FLOW_KEYS:
pointer_desc = "flow keys ";
break;
case PTR_TO_MAP_VALUE:
pointer_desc = "value ";
break;
case PTR_TO_CTX:
pointer_desc = "context ";
break;
case PTR_TO_STACK:
pointer_desc = "stack ";
/* The stack spill tracking logic in check_stack_write()
* and check_stack_read() relies on stack accesses being
* aligned.
*/
strict = true;
break;
case PTR_TO_SOCKET:
pointer_desc = "sock ";
break;
case PTR_TO_SOCK_COMMON:
pointer_desc = "sock_common ";
break;
case PTR_TO_TCP_SOCK:
pointer_desc = "tcp_sock ";
break;
default:
break;
}
return check_generic_ptr_alignment(env, reg, pointer_desc, off, size,
strict);
}
static int update_stack_depth(struct bpf_verifier_env *env,
const struct bpf_func_state *func,
int off)
{
u16 stack = env->subprog_info[func->subprogno].stack_depth;
if (stack >= -off)
return 0;
/* update known max for given subprogram */
env->subprog_info[func->subprogno].stack_depth = -off;
return 0;
}
/* starting from main bpf function walk all instructions of the function
* and recursively walk all callees that given function can call.
* Ignore jump and exit insns.
* Since recursion is prevented by check_cfg() this algorithm
* only needs a local stack of MAX_CALL_FRAMES to remember callsites
*/
static int check_max_stack_depth(struct bpf_verifier_env *env)
{
int depth = 0, frame = 0, idx = 0, i = 0, subprog_end;
struct bpf_subprog_info *subprog = env->subprog_info;
struct bpf_insn *insn = env->prog->insnsi;
int ret_insn[MAX_CALL_FRAMES];
int ret_prog[MAX_CALL_FRAMES];
process_func:
/* round up to 32-bytes, since this is granularity
* of interpreter stack size
*/
depth += round_up(max_t(u32, subprog[idx].stack_depth, 1), 32);
if (depth > MAX_BPF_STACK) {
verbose(env, "combined stack size of %d calls is %d. Too large\n",
frame + 1, depth);
return -EACCES;
}
continue_func:
subprog_end = subprog[idx + 1].start;
for (; i < subprog_end; i++) {
if (insn[i].code != (BPF_JMP | BPF_CALL))
continue;
if (insn[i].src_reg != BPF_PSEUDO_CALL)
continue;
/* remember insn and function to return to */
ret_insn[frame] = i + 1;
ret_prog[frame] = idx;
/* find the callee */
i = i + insn[i].imm + 1;
idx = find_subprog(env, i);
if (idx < 0) {
WARN_ONCE(1, "verifier bug. No program starts at insn %d\n",
i);
return -EFAULT;
}
frame++;
if (frame >= MAX_CALL_FRAMES) {
verbose(env, "the call stack of %d frames is too deep !\n",
frame);
return -E2BIG;
}
goto process_func;
}
/* end of for() loop means the last insn of the 'subprog'
* was reached. Doesn't matter whether it was JA or EXIT
*/
if (frame == 0)
return 0;
depth -= round_up(max_t(u32, subprog[idx].stack_depth, 1), 32);
frame--;
i = ret_insn[frame];
idx = ret_prog[frame];
goto continue_func;
}
#ifndef CONFIG_BPF_JIT_ALWAYS_ON
static int get_callee_stack_depth(struct bpf_verifier_env *env,
const struct bpf_insn *insn, int idx)
{
int start = idx + insn->imm + 1, subprog;
subprog = find_subprog(env, start);
if (subprog < 0) {
WARN_ONCE(1, "verifier bug. No program starts at insn %d\n",
start);
return -EFAULT;
}
return env->subprog_info[subprog].stack_depth;
}
#endif
static int check_ctx_reg(struct bpf_verifier_env *env,
const struct bpf_reg_state *reg, int regno)
{
/* Access to ctx or passing it to a helper is only allowed in
* its original, unmodified form.
*/
if (reg->off) {
verbose(env, "dereference of modified ctx ptr R%d off=%d disallowed\n",
regno, reg->off);
return -EACCES;
}
if (!tnum_is_const(reg->var_off) || reg->var_off.value) {
char tn_buf[48];
tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
verbose(env, "variable ctx access var_off=%s disallowed\n", tn_buf);
return -EACCES;
}
return 0;
}
/* truncate register to smaller size (in bytes)
* must be called with size < BPF_REG_SIZE
*/
static void coerce_reg_to_size(struct bpf_reg_state *reg, int size)
{
u64 mask;
/* clear high bits in bit representation */
reg->var_off = tnum_cast(reg->var_off, size);
/* fix arithmetic bounds */
mask = ((u64)1 << (size * 8)) - 1;
if ((reg->umin_value & ~mask) == (reg->umax_value & ~mask)) {
reg->umin_value &= mask;
reg->umax_value &= mask;
} else {
reg->umin_value = 0;
reg->umax_value = mask;
}
reg->smin_value = reg->umin_value;
reg->smax_value = reg->umax_value;
}
/* check whether memory at (regno + off) is accessible for t = (read | write)
* if t==write, value_regno is a register which value is stored into memory
* if t==read, value_regno is a register which will receive the value from memory
* if t==write && value_regno==-1, some unknown value is stored into memory
* if t==read && value_regno==-1, don't care what we read from memory
*/
static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regno,
int off, int bpf_size, enum bpf_access_type t,
int value_regno, bool strict_alignment_once)
{
struct bpf_reg_state *regs = cur_regs(env);
struct bpf_reg_state *reg = regs + regno;
struct bpf_func_state *state;
int size, err = 0;
size = bpf_size_to_bytes(bpf_size);
if (size < 0)
return size;
/* alignment checks will add in reg->off themselves */
err = check_ptr_alignment(env, reg, off, size, strict_alignment_once);
if (err)
return err;
/* for access checks, reg->off is just part of off */
off += reg->off;
if (reg->type == PTR_TO_MAP_VALUE) {
if (t == BPF_WRITE && value_regno >= 0 &&
is_pointer_value(env, value_regno)) {
verbose(env, "R%d leaks addr into map\n", value_regno);
return -EACCES;
}
err = check_map_access(env, regno, off, size, false);
if (!err && t == BPF_READ && value_regno >= 0)
mark_reg_unknown(env, regs, value_regno);
} else if (reg->type == PTR_TO_CTX) {
enum bpf_reg_type reg_type = SCALAR_VALUE;
if (t == BPF_WRITE && value_regno >= 0 &&
is_pointer_value(env, value_regno)) {
verbose(env, "R%d leaks addr into ctx\n", value_regno);
return -EACCES;
}
err = check_ctx_reg(env, reg, regno);
if (err < 0)
return err;
err = check_ctx_access(env, insn_idx, off, size, t, &reg_type);
if (!err && t == BPF_READ && value_regno >= 0) {
/* ctx access returns either a scalar, or a
* PTR_TO_PACKET[_META,_END]. In the latter
* case, we know the offset is zero.
*/
if (reg_type == SCALAR_VALUE) {
mark_reg_unknown(env, regs, value_regno);
} else {
mark_reg_known_zero(env, regs,
value_regno);
if (reg_type_may_be_null(reg_type))
regs[value_regno].id = ++env->id_gen;
}
regs[value_regno].type = reg_type;
}
} else if (reg->type == PTR_TO_STACK) {
off += reg->var_off.value;
err = check_stack_access(env, reg, off, size);
if (err)
return err;
state = func(env, reg);
err = update_stack_depth(env, state, off);
if (err)
return err;
if (t == BPF_WRITE)
err = check_stack_write(env, state, off, size,
value_regno, insn_idx);
else
err = check_stack_read(env, state, off, size,
value_regno);
} else if (reg_is_pkt_pointer(reg)) {
if (t == BPF_WRITE && !may_access_direct_pkt_data(env, NULL, t)) {
verbose(env, "cannot write into packet\n");
return -EACCES;
}
if (t == BPF_WRITE && value_regno >= 0 &&
is_pointer_value(env, value_regno)) {
verbose(env, "R%d leaks addr into packet\n",
value_regno);
return -EACCES;
}
err = check_packet_access(env, regno, off, size, false);
if (!err && t == BPF_READ && value_regno >= 0)
mark_reg_unknown(env, regs, value_regno);
} else if (reg->type == PTR_TO_FLOW_KEYS) {
if (t == BPF_WRITE && value_regno >= 0 &&
is_pointer_value(env, value_regno)) {
verbose(env, "R%d leaks addr into flow keys\n",
value_regno);
return -EACCES;
}
err = check_flow_keys_access(env, off, size);
if (!err && t == BPF_READ && value_regno >= 0)
mark_reg_unknown(env, regs, value_regno);
} else if (type_is_sk_pointer(reg->type)) {
if (t == BPF_WRITE) {
verbose(env, "R%d cannot write into %s\n",
regno, reg_type_str[reg->type]);
return -EACCES;
}
err = check_sock_access(env, insn_idx, regno, off, size, t);
if (!err && value_regno >= 0)
mark_reg_unknown(env, regs, value_regno);
} else {
verbose(env, "R%d invalid mem access '%s'\n", regno,
reg_type_str[reg->type]);
return -EACCES;
}
if (!err && size < BPF_REG_SIZE && value_regno >= 0 && t == BPF_READ &&
regs[value_regno].type == SCALAR_VALUE) {
/* b/h/w load zero-extends, mark upper bits as known 0 */
coerce_reg_to_size(&regs[value_regno], size);
}
return err;
}
static int check_xadd(struct bpf_verifier_env *env, int insn_idx, struct bpf_insn *insn)
{
int err;
if ((BPF_SIZE(insn->code) != BPF_W && BPF_SIZE(insn->code) != BPF_DW) ||
insn->imm != 0) {
verbose(env, "BPF_XADD uses reserved fields\n");
return -EINVAL;
}
/* check src1 operand */
err = check_reg_arg(env, insn->src_reg, SRC_OP);
if (err)
return err;
/* check src2 operand */
err = check_reg_arg(env, insn->dst_reg, SRC_OP);
if (err)
return err;
if (is_pointer_value(env, insn->src_reg)) {
verbose(env, "R%d leaks addr into mem\n", insn->src_reg);
return -EACCES;
}
if (is_ctx_reg(env, insn->dst_reg) ||
is_pkt_reg(env, insn->dst_reg) ||
is_flow_key_reg(env, insn->dst_reg) ||
is_sk_reg(env, insn->dst_reg)) {
verbose(env, "BPF_XADD stores into R%d %s is not allowed\n",
insn->dst_reg,
reg_type_str[reg_state(env, insn->dst_reg)->type]);
return -EACCES;
}
/* check whether atomic_add can read the memory */
err = check_mem_access(env, insn_idx, insn->dst_reg, insn->off,
BPF_SIZE(insn->code), BPF_READ, -1, true);
if (err)
return err;
/* check whether atomic_add can write into the same memory */
return check_mem_access(env, insn_idx, insn->dst_reg, insn->off,
BPF_SIZE(insn->code), BPF_WRITE, -1, true);
}
/* when register 'regno' is passed into function that will read 'access_size'
* bytes from that pointer, make sure that it's within stack boundary
* and all elements of stack are initialized.
* Unlike most pointer bounds-checking functions, this one doesn't take an
* 'off' argument, so it has to add in reg->off itself.
*/
static int check_stack_boundary(struct bpf_verifier_env *env, int regno,
int access_size, bool zero_size_allowed,
struct bpf_call_arg_meta *meta)
{
struct bpf_reg_state *reg = reg_state(env, regno);
struct bpf_func_state *state = func(env, reg);
int off, i, slot, spi;
if (reg->type != PTR_TO_STACK) {
/* Allow zero-byte read from NULL, regardless of pointer type */
if (zero_size_allowed && access_size == 0 &&
register_is_null(reg))
return 0;
verbose(env, "R%d type=%s expected=%s\n", regno,
reg_type_str[reg->type],
reg_type_str[PTR_TO_STACK]);
return -EACCES;
}
/* Only allow fixed-offset stack reads */
if (!tnum_is_const(reg->var_off)) {
char tn_buf[48];
tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
verbose(env, "invalid variable stack read R%d var_off=%s\n",
regno, tn_buf);
return -EACCES;
}
off = reg->off + reg->var_off.value;
if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 ||
access_size < 0 || (access_size == 0 && !zero_size_allowed)) {
verbose(env, "invalid stack type R%d off=%d access_size=%d\n",
regno, off, access_size);
return -EACCES;
}
if (meta && meta->raw_mode) {
meta->access_size = access_size;
meta->regno = regno;
return 0;
}
for (i = 0; i < access_size; i++) {
u8 *stype;
slot = -(off + i) - 1;
spi = slot / BPF_REG_SIZE;
if (state->allocated_stack <= slot)
goto err;
stype = &state->stack[spi].slot_type[slot % BPF_REG_SIZE];
if (*stype == STACK_MISC)
goto mark;
if (*stype == STACK_ZERO) {
/* helper can write anything into the stack */
*stype = STACK_MISC;
goto mark;
}
err:
verbose(env, "invalid indirect read from stack off %d+%d size %d\n",
off, i, access_size);
return -EACCES;
mark:
/* reading any byte out of 8-byte 'spill_slot' will cause
* the whole slot to be marked as 'read'
*/
mark_reg_read(env, &state->stack[spi].spilled_ptr,
state->stack[spi].spilled_ptr.parent);
}
return update_stack_depth(env, state, off);
}
static int check_helper_mem_access(struct bpf_verifier_env *env, int regno,
int access_size, bool zero_size_allowed,
struct bpf_call_arg_meta *meta)
{
struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];
switch (reg->type) {
case PTR_TO_PACKET:
case PTR_TO_PACKET_META:
return check_packet_access(env, regno, reg->off, access_size,
zero_size_allowed);
case PTR_TO_MAP_VALUE:
return check_map_access(env, regno, reg->off, access_size,
zero_size_allowed);
default: /* scalar_value|ptr_to_stack or invalid ptr */
return check_stack_boundary(env, regno, access_size,
zero_size_allowed, meta);
}
}
/* Implementation details:
* bpf_map_lookup returns PTR_TO_MAP_VALUE_OR_NULL
* Two bpf_map_lookups (even with the same key) will have different reg->id.
* For traditional PTR_TO_MAP_VALUE the verifier clears reg->id after
* value_or_null->value transition, since the verifier only cares about
* the range of access to valid map value pointer and doesn't care about actual
* address of the map element.
* For maps with 'struct bpf_spin_lock' inside map value the verifier keeps
* reg->id > 0 after value_or_null->value transition. By doing so
* two bpf_map_lookups will be considered two different pointers that
* point to different bpf_spin_locks.
* The verifier allows taking only one bpf_spin_lock at a time to avoid
* dead-locks.
* Since only one bpf_spin_lock is allowed the checks are simpler than
* reg_is_refcounted() logic. The verifier needs to remember only
* one spin_lock instead of array of acquired_refs.
* cur_state->active_spin_lock remembers which map value element got locked
* and clears it after bpf_spin_unlock.
*/
static int process_spin_lock(struct bpf_verifier_env *env, int regno,
bool is_lock)
{
struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];
struct bpf_verifier_state *cur = env->cur_state;
bool is_const = tnum_is_const(reg->var_off);
struct bpf_map *map = reg->map_ptr;
u64 val = reg->var_off.value;
if (reg->type != PTR_TO_MAP_VALUE) {
verbose(env, "R%d is not a pointer to map_value\n", regno);
return -EINVAL;
}
if (!is_const) {
verbose(env,
"R%d doesn't have constant offset. bpf_spin_lock has to be at the constant offset\n",
regno);
return -EINVAL;
}
if (!map->btf) {
verbose(env,
"map '%s' has to have BTF in order to use bpf_spin_lock\n",
map->name);
return -EINVAL;
}
if (!map_value_has_spin_lock(map)) {
if (map->spin_lock_off == -E2BIG)
verbose(env,
"map '%s' has more than one 'struct bpf_spin_lock'\n",
map->name);
else if (map->spin_lock_off == -ENOENT)
verbose(env,
"map '%s' doesn't have 'struct bpf_spin_lock'\n",
map->name);
else
verbose(env,
"map '%s' is not a struct type or bpf_spin_lock is mangled\n",
map->name);
return -EINVAL;
}
if (map->spin_lock_off != val + reg->off) {
verbose(env, "off %lld doesn't point to 'struct bpf_spin_lock'\n",
val + reg->off);
return -EINVAL;
}
if (is_lock) {
if (cur->active_spin_lock) {
verbose(env,
"Locking two bpf_spin_locks are not allowed\n");
return -EINVAL;
}
cur->active_spin_lock = reg->id;
} else {
if (!cur->active_spin_lock) {
verbose(env, "bpf_spin_unlock without taking a lock\n");
return -EINVAL;
}
if (cur->active_spin_lock != reg->id) {
verbose(env, "bpf_spin_unlock of different lock\n");
return -EINVAL;
}
cur->active_spin_lock = 0;
}
return 0;
}
static bool arg_type_is_mem_ptr(enum bpf_arg_type type)
{
return type == ARG_PTR_TO_MEM ||
type == ARG_PTR_TO_MEM_OR_NULL ||
type == ARG_PTR_TO_UNINIT_MEM;
}
static bool arg_type_is_mem_size(enum bpf_arg_type type)
{
return type == ARG_CONST_SIZE ||
type == ARG_CONST_SIZE_OR_ZERO;
}
static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
enum bpf_arg_type arg_type,
struct bpf_call_arg_meta *meta)
{
struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];
enum bpf_reg_type expected_type, type = reg->type;
int err = 0;
if (arg_type == ARG_DONTCARE)
return 0;
err = check_reg_arg(env, regno, SRC_OP);
if (err)
return err;
if (arg_type == ARG_ANYTHING) {
if (is_pointer_value(env, regno)) {
verbose(env, "R%d leaks addr into helper function\n",
regno);
return -EACCES;
}
return 0;
}
if (type_is_pkt_pointer(type) &&
!may_access_direct_pkt_data(env, meta, BPF_READ)) {
verbose(env, "helper access to the packet is not allowed\n");
return -EACCES;
}
if (arg_type == ARG_PTR_TO_MAP_KEY ||
arg_type == ARG_PTR_TO_MAP_VALUE ||
arg_type == ARG_PTR_TO_UNINIT_MAP_VALUE) {
expected_type = PTR_TO_STACK;
if (!type_is_pkt_pointer(type) && type != PTR_TO_MAP_VALUE &&
type != expected_type)
goto err_type;
} else if (arg_type == ARG_CONST_SIZE ||
arg_type == ARG_CONST_SIZE_OR_ZERO) {
expected_type = SCALAR_VALUE;
if (type != expected_type)
goto err_type;
} else if (arg_type == ARG_CONST_MAP_PTR) {
expected_type = CONST_PTR_TO_MAP;
if (type != expected_type)
goto err_type;
} else if (arg_type == ARG_PTR_TO_CTX) {
expected_type = PTR_TO_CTX;
if (type != expected_type)
goto err_type;
err = check_ctx_reg(env, reg, regno);
if (err < 0)
return err;
} else if (arg_type == ARG_PTR_TO_SOCK_COMMON) {
expected_type = PTR_TO_SOCK_COMMON;
/* Any sk pointer can be ARG_PTR_TO_SOCK_COMMON */
if (!type_is_sk_pointer(type))
goto err_type;
if (reg->ref_obj_id) {
if (meta->ref_obj_id) {
verbose(env, "verifier internal error: more than one arg with ref_obj_id R%d %u %u\n",
regno, reg->ref_obj_id,
meta->ref_obj_id);
return -EFAULT;
}
meta->ref_obj_id = reg->ref_obj_id;
}
} else if (arg_type == ARG_PTR_TO_SPIN_LOCK) {
if (meta->func_id == BPF_FUNC_spin_lock) {
if (process_spin_lock(env, regno, true))
return -EACCES;
} else if (meta->func_id == BPF_FUNC_spin_unlock) {
if (process_spin_lock(env, regno, false))
return -EACCES;
} else {
verbose(env, "verifier internal error\n");
return -EFAULT;
}
} else if (arg_type_is_mem_ptr(arg_type)) {
expected_type = PTR_TO_STACK;
/* One exception here. In case function allows for NULL to be
* passed in as argument, it's a SCALAR_VALUE type. Final test
* happens during stack boundary checking.
*/
if (register_is_null(reg) &&
arg_type == ARG_PTR_TO_MEM_OR_NULL)
/* final test in check_stack_boundary() */;
else if (!type_is_pkt_pointer(type) &&
type != PTR_TO_MAP_VALUE &&
type != expected_type)
goto err_type;
meta->raw_mode = arg_type == ARG_PTR_TO_UNINIT_MEM;
} else {
verbose(env, "unsupported arg_type %d\n", arg_type);
return -EFAULT;
}
if (arg_type == ARG_CONST_MAP_PTR) {
/* bpf_map_xxx(map_ptr) call: remember that map_ptr */
meta->map_ptr = reg->map_ptr;
} else if (arg_type == ARG_PTR_TO_MAP_KEY) {
/* bpf_map_xxx(..., map_ptr, ..., key) call:
* check that [key, key + map->key_size) are within
* stack limits and initialized
*/
if (!meta->map_ptr) {
/* in function declaration map_ptr must come before
* map_key, so that it's verified and known before
* we have to check map_key here. Otherwise it means
* that kernel subsystem misconfigured verifier
*/
verbose(env, "invalid map_ptr to access map->key\n");
return -EACCES;
}
err = check_helper_mem_access(env, regno,
meta->map_ptr->key_size, false,
NULL);
} else if (arg_type == ARG_PTR_TO_MAP_VALUE ||
arg_type == ARG_PTR_TO_UNINIT_MAP_VALUE) {
/* bpf_map_xxx(..., map_ptr, ..., value) call:
* check [value, value + map->value_size) validity
*/
if (!meta->map_ptr) {
/* kernel subsystem misconfigured verifier */
verbose(env, "invalid map_ptr to access map->value\n");
return -EACCES;
}
meta->raw_mode = (arg_type == ARG_PTR_TO_UNINIT_MAP_VALUE);
err = check_helper_mem_access(env, regno,
meta->map_ptr->value_size, false,
meta);
} else if (arg_type_is_mem_size(arg_type)) {
bool zero_size_allowed = (arg_type == ARG_CONST_SIZE_OR_ZERO);
/* remember the mem_size which may be used later
* to refine return values.
*/
meta->msize_smax_value = reg->smax_value;
meta->msize_umax_value = reg->umax_value;
/* The register is SCALAR_VALUE; the access check
* happens using its boundaries.
*/
if (!tnum_is_const(reg->var_off))
/* For unprivileged variable accesses, disable raw
* mode so that the program is required to
* initialize all the memory that the helper could
* just partially fill up.
*/
meta = NULL;
if (reg->smin_value < 0) {
verbose(env, "R%d min value is negative, either use unsigned or 'var &= const'\n",
regno);
return -EACCES;
}
if (reg->umin_value == 0) {
err = check_helper_mem_access(env, regno - 1, 0,
zero_size_allowed,
meta);
if (err)
return err;
}
if (reg->umax_value >= BPF_MAX_VAR_SIZ) {
verbose(env, "R%d unbounded memory access, use 'var &= const' or 'if (var < const)'\n",
regno);
return -EACCES;
}
err = check_helper_mem_access(env, regno - 1,
reg->umax_value,
zero_size_allowed, meta);
}
return err;
err_type:
verbose(env, "R%d type=%s expected=%s\n", regno,
reg_type_str[type], reg_type_str[expected_type]);
return -EACCES;
}
static int check_map_func_compatibility(struct bpf_verifier_env *env,
struct bpf_map *map, int func_id)
{
if (!map)
return 0;
/* We need a two way check, first is from map perspective ... */
switch (map->map_type) {
case BPF_MAP_TYPE_PROG_ARRAY:
if (func_id != BPF_FUNC_tail_call)
goto error;
break;
case BPF_MAP_TYPE_PERF_EVENT_ARRAY:
if (func_id != BPF_FUNC_perf_event_read &&
func_id != BPF_FUNC_perf_event_output &&
func_id != BPF_FUNC_perf_event_read_value)
goto error;
break;
case BPF_MAP_TYPE_STACK_TRACE:
if (func_id != BPF_FUNC_get_stackid)
goto error;
break;
case BPF_MAP_TYPE_CGROUP_ARRAY:
if (func_id != BPF_FUNC_skb_under_cgroup &&
func_id != BPF_FUNC_current_task_under_cgroup)
goto error;
break;
case BPF_MAP_TYPE_CGROUP_STORAGE:
case BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE:
if (func_id != BPF_FUNC_get_local_storage)
goto error;
break;
/* devmap returns a pointer to a live net_device ifindex that we cannot
* allow to be modified from bpf side. So do not allow lookup elements
* for now.
*/
case BPF_MAP_TYPE_DEVMAP:
if (func_id != BPF_FUNC_redirect_map)
goto error;
break;
/* Restrict bpf side of cpumap and xskmap, open when use-cases
* appear.
*/
case BPF_MAP_TYPE_CPUMAP:
case BPF_MAP_TYPE_XSKMAP:
if (func_id != BPF_FUNC_redirect_map)
goto error;
break;
case BPF_MAP_TYPE_ARRAY_OF_MAPS:
case BPF_MAP_TYPE_HASH_OF_MAPS:
if (func_id != BPF_FUNC_map_lookup_elem)
goto error;
break;
case BPF_MAP_TYPE_SOCKMAP:
if (func_id != BPF_FUNC_sk_redirect_map &&
func_id != BPF_FUNC_sock_map_update &&
func_id != BPF_FUNC_map_delete_elem &&
func_id != BPF_FUNC_msg_redirect_map)
goto error;
break;
case BPF_MAP_TYPE_SOCKHASH:
if (func_id != BPF_FUNC_sk_redirect_hash &&
func_id != BPF_FUNC_sock_hash_update &&
func_id != BPF_FUNC_map_delete_elem &&
func_id != BPF_FUNC_msg_redirect_hash)
goto error;
break;
case BPF_MAP_TYPE_REUSEPORT_SOCKARRAY:
if (func_id != BPF_FUNC_sk_select_reuseport)
goto error;
break;
case BPF_MAP_TYPE_QUEUE:
case BPF_MAP_TYPE_STACK:
if (func_id != BPF_FUNC_map_peek_elem &&
func_id != BPF_FUNC_map_pop_elem &&
func_id != BPF_FUNC_map_push_elem)
goto error;
break;
default:
break;
}
/* ... and second from the function itself. */
switch (func_id) {
case BPF_FUNC_tail_call:
if (map->map_type != BPF_MAP_TYPE_PROG_ARRAY)
goto error;
if (env->subprog_cnt > 1) {
verbose(env, "tail_calls are not allowed in programs with bpf-to-bpf calls\n");
return -EINVAL;
}
break;
case BPF_FUNC_perf_event_read:
case BPF_FUNC_perf_event_output:
case BPF_FUNC_perf_event_read_value:
if (map->map_type != BPF_MAP_TYPE_PERF_EVENT_ARRAY)
goto error;
break;
case BPF_FUNC_get_stackid:
if (map->map_type != BPF_MAP_TYPE_STACK_TRACE)
goto error;
break;
case BPF_FUNC_current_task_under_cgroup:
case BPF_FUNC_skb_under_cgroup:
if (map->map_type != BPF_MAP_TYPE_CGROUP_ARRAY)
goto error;
break;
case BPF_FUNC_redirect_map:
if (map->map_type != BPF_MAP_TYPE_DEVMAP &&
map->map_type != BPF_MAP_TYPE_CPUMAP &&
map->map_type != BPF_MAP_TYPE_XSKMAP)
goto error;
break;
case BPF_FUNC_sk_redirect_map:
case BPF_FUNC_msg_redirect_map:
case BPF_FUNC_sock_map_update:
if (map->map_type != BPF_MAP_TYPE_SOCKMAP)
goto error;
break;
case BPF_FUNC_sk_redirect_hash:
case BPF_FUNC_msg_redirect_hash:
case BPF_FUNC_sock_hash_update:
if (map->map_type != BPF_MAP_TYPE_SOCKHASH)
goto error;
break;
case BPF_FUNC_get_local_storage:
if (map->map_type != BPF_MAP_TYPE_CGROUP_STORAGE &&
map->map_type != BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE)
goto error;
break;
case BPF_FUNC_sk_select_reuseport:
if (map->map_type != BPF_MAP_TYPE_REUSEPORT_SOCKARRAY)
goto error;
break;
case BPF_FUNC_map_peek_elem:
case BPF_FUNC_map_pop_elem:
case BPF_FUNC_map_push_elem:
if (map->map_type != BPF_MAP_TYPE_QUEUE &&
map->map_type != BPF_MAP_TYPE_STACK)
goto error;
break;
default:
break;
}
return 0;
error:
verbose(env, "cannot pass map_type %d into func %s#%d\n",
map->map_type, func_id_name(func_id), func_id);
return -EINVAL;
}
static bool check_raw_mode_ok(const struct bpf_func_proto *fn)
{
int count = 0;
if (fn->arg1_type == ARG_PTR_TO_UNINIT_MEM)
count++;
if (fn->arg2_type == ARG_PTR_TO_UNINIT_MEM)
count++;
if (fn->arg3_type == ARG_PTR_TO_UNINIT_MEM)
count++;
if (fn->arg4_type == ARG_PTR_TO_UNINIT_MEM)
count++;
if (fn->arg5_type == ARG_PTR_TO_UNINIT_MEM)
count++;
/* We only support one arg being in raw mode at the moment,
* which is sufficient for the helper functions we have
* right now.
*/
return count <= 1;
}
static bool check_args_pair_invalid(enum bpf_arg_type arg_curr,
enum bpf_arg_type arg_next)
{
return (arg_type_is_mem_ptr(arg_curr) &&
!arg_type_is_mem_size(arg_next)) ||
(!arg_type_is_mem_ptr(arg_curr) &&
arg_type_is_mem_size(arg_next));
}
static bool check_arg_pair_ok(const struct bpf_func_proto *fn)
{
/* bpf_xxx(..., buf, len) call will access 'len'
* bytes from memory 'buf'. Both arg types need
* to be paired, so make sure there's no buggy
* helper function specification.
*/
if (arg_type_is_mem_size(fn->arg1_type) ||
arg_type_is_mem_ptr(fn->arg5_type) ||
check_args_pair_invalid(fn->arg1_type, fn->arg2_type) ||
check_args_pair_invalid(fn->arg2_type, fn->arg3_type) ||
check_args_pair_invalid(fn->arg3_type, fn->arg4_type) ||
check_args_pair_invalid(fn->arg4_type, fn->arg5_type))
return false;
return true;
}
static bool check_refcount_ok(const struct bpf_func_proto *fn, int func_id)
{
int count = 0;
if (arg_type_may_be_refcounted(fn->arg1_type))
count++;
if (arg_type_may_be_refcounted(fn->arg2_type))
count++;
if (arg_type_may_be_refcounted(fn->arg3_type))
count++;
if (arg_type_may_be_refcounted(fn->arg4_type))
count++;
if (arg_type_may_be_refcounted(fn->arg5_type))
count++;
/* A reference acquiring function cannot acquire
* another refcounted ptr.
*/
if (is_acquire_function(func_id) && count)
return false;
/* We only support one arg being unreferenced at the moment,
* which is sufficient for the helper functions we have right now.
*/
return count <= 1;
}
static int check_func_proto(const struct bpf_func_proto *fn, int func_id)
{
return check_raw_mode_ok(fn) &&
check_arg_pair_ok(fn) &&
check_refcount_ok(fn, func_id) ? 0 : -EINVAL;
}
/* Packet data might have moved, any old PTR_TO_PACKET[_META,_END]
* are now invalid, so turn them into unknown SCALAR_VALUE.
*/
static void __clear_all_pkt_pointers(struct bpf_verifier_env *env,
struct bpf_func_state *state)
{
struct bpf_reg_state *regs = state->regs, *reg;
int i;
for (i = 0; i < MAX_BPF_REG; i++)
if (reg_is_pkt_pointer_any(&regs[i]))
mark_reg_unknown(env, regs, i);
bpf_for_each_spilled_reg(i, state, reg) {
if (!reg)
continue;
if (reg_is_pkt_pointer_any(reg))
__mark_reg_unknown(reg);
}
}
static void clear_all_pkt_pointers(struct bpf_verifier_env *env)
{
struct bpf_verifier_state *vstate = env->cur_state;
int i;
for (i = 0; i <= vstate->curframe; i++)
__clear_all_pkt_pointers(env, vstate->frame[i]);
}
static void release_reg_references(struct bpf_verifier_env *env,
struct bpf_func_state *state,
int ref_obj_id)
{
struct bpf_reg_state *regs = state->regs, *reg;
int i;
for (i = 0; i < MAX_BPF_REG; i++)
if (regs[i].ref_obj_id == ref_obj_id)
mark_reg_unknown(env, regs, i);
bpf_for_each_spilled_reg(i, state, reg) {
if (!reg)
continue;
if (reg->ref_obj_id == ref_obj_id)
__mark_reg_unknown(reg);
}
}
/* The pointer with the specified id has released its reference to kernel
* resources. Identify all copies of the same pointer and clear the reference.
*/
static int release_reference(struct bpf_verifier_env *env,
int ref_obj_id)
{
struct bpf_verifier_state *vstate = env->cur_state;
int err;
int i;
err = release_reference_state(cur_func(env), ref_obj_id);
if (err)
return err;
for (i = 0; i <= vstate->curframe; i++)
release_reg_references(env, vstate->frame[i], ref_obj_id);
return 0;
}
static int check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
int *insn_idx)
{
struct bpf_verifier_state *state = env->cur_state;
struct bpf_func_state *caller, *callee;
int i, err, subprog, target_insn;
if (state->curframe + 1 >= MAX_CALL_FRAMES) {
verbose(env, "the call stack of %d frames is too deep\n",
state->curframe + 2);
return -E2BIG;
}
target_insn = *insn_idx + insn->imm;
subprog = find_subprog(env, target_insn + 1);
if (subprog < 0) {
verbose(env, "verifier bug. No program starts at insn %d\n",
target_insn + 1);
return -EFAULT;
}
caller = state->frame[state->curframe];
if (state->frame[state->curframe + 1]) {
verbose(env, "verifier bug. Frame %d already allocated\n",
state->curframe + 1);
return -EFAULT;
}
callee = kzalloc(sizeof(*callee), GFP_KERNEL);
if (!callee)
return -ENOMEM;
state->frame[state->curframe + 1] = callee;
/* callee cannot access r0, r6 - r9 for reading and has to write
* into its own stack before reading from it.
* callee can read/write into caller's stack
*/
init_func_state(env, callee,
/* remember the callsite, it will be used by bpf_exit */
*insn_idx /* callsite */,
state->curframe + 1 /* frameno within this callchain */,
subprog /* subprog number within this prog */);
/* Transfer references to the callee */
err = transfer_reference_state(callee, caller);
if (err)
return err;
/* copy r1 - r5 args that callee can access. The copy includes parent
* pointers, which connects us up to the liveness chain
*/
for (i = BPF_REG_1; i <= BPF_REG_5; i++)
callee->regs[i] = caller->regs[i];
/* after the call registers r0 - r5 were scratched */
for (i = 0; i < CALLER_SAVED_REGS; i++) {
mark_reg_not_init(env, caller->regs, caller_saved[i]);
check_reg_arg(env, caller_saved[i], DST_OP_NO_MARK);
}
/* only increment it after check_reg_arg() finished */
state->curframe++;
/* and go analyze first insn of the callee */
*insn_idx = target_insn;
if (env->log.level) {
verbose(env, "caller:\n");
print_verifier_state(env, caller);
verbose(env, "callee:\n");
print_verifier_state(env, callee);
}
return 0;
}
static int prepare_func_exit(struct bpf_verifier_env *env, int *insn_idx)
{
struct bpf_verifier_state *state = env->cur_state;
struct bpf_func_state *caller, *callee;
struct bpf_reg_state *r0;
int err;
callee = state->frame[state->curframe];
r0 = &callee->regs[BPF_REG_0];
if (r0->type == PTR_TO_STACK) {
/* technically it's ok to return caller's stack pointer
* (or caller's caller's pointer) back to the caller,
* since these pointers are valid. Only current stack
* pointer will be invalid as soon as function exits,
* but let's be conservative
*/
verbose(env, "cannot return stack pointer to the caller\n");
return -EINVAL;
}
state->curframe--;
caller = state->frame[state->curframe];
/* return to the caller whatever r0 had in the callee */
caller->regs[BPF_REG_0] = *r0;
/* Transfer references to the caller */
err = transfer_reference_state(caller, callee);
if (err)
return err;
*insn_idx = callee->callsite + 1;
if (env->log.level) {
verbose(env, "returning from callee:\n");
print_verifier_state(env, callee);
verbose(env, "to caller at %d:\n", *insn_idx);
print_verifier_state(env, caller);
}
/* clear everything in the callee */
free_func_state(callee);
state->frame[state->curframe + 1] = NULL;
return 0;
}
static void do_refine_retval_range(struct bpf_reg_state *regs, int ret_type,
int func_id,
struct bpf_call_arg_meta *meta)
{
struct bpf_reg_state *ret_reg = &regs[BPF_REG_0];
if (ret_type != RET_INTEGER ||
(func_id != BPF_FUNC_get_stack &&
func_id != BPF_FUNC_probe_read_str))
return;
ret_reg->smax_value = meta->msize_smax_value;
ret_reg->umax_value = meta->msize_umax_value;
__reg_deduce_bounds(ret_reg);
__reg_bound_offset(ret_reg);
}
static int
record_func_map(struct bpf_verifier_env *env, struct bpf_call_arg_meta *meta,
int func_id, int insn_idx)
{
struct bpf_insn_aux_data *aux = &env->insn_aux_data[insn_idx];
if (func_id != BPF_FUNC_tail_call &&
func_id != BPF_FUNC_map_lookup_elem &&
func_id != BPF_FUNC_map_update_elem &&
func_id != BPF_FUNC_map_delete_elem &&
func_id != BPF_FUNC_map_push_elem &&
func_id != BPF_FUNC_map_pop_elem &&
func_id != BPF_FUNC_map_peek_elem)
return 0;
if (meta->map_ptr == NULL) {
verbose(env, "kernel subsystem misconfigured verifier\n");
return -EINVAL;
}
if (!BPF_MAP_PTR(aux->map_state))
bpf_map_ptr_store(aux, meta->map_ptr,
meta->map_ptr->unpriv_array);
else if (BPF_MAP_PTR(aux->map_state) != meta->map_ptr)
bpf_map_ptr_store(aux, BPF_MAP_PTR_POISON,
meta->map_ptr->unpriv_array);
return 0;
}
static int check_reference_leak(struct bpf_verifier_env *env)
{
struct bpf_func_state *state = cur_func(env);
int i;
for (i = 0; i < state->acquired_refs; i++) {
verbose(env, "Unreleased reference id=%d alloc_insn=%d\n",
state->refs[i].id, state->refs[i].insn_idx);
}
return state->acquired_refs ? -EINVAL : 0;
}
static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn_idx)
{
const struct bpf_func_proto *fn = NULL;
struct bpf_reg_state *regs;
struct bpf_call_arg_meta meta;
bool changes_data;
int i, err;
/* find function prototype */
if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) {
verbose(env, "invalid func %s#%d\n", func_id_name(func_id),
func_id);
return -EINVAL;
}
if (env->ops->get_func_proto)
fn = env->ops->get_func_proto(func_id, env->prog);
if (!fn) {
verbose(env, "unknown func %s#%d\n", func_id_name(func_id),
func_id);
return -EINVAL;
}
/* eBPF programs must be GPL compatible to use GPL-ed functions */
if (!env->prog->gpl_compatible && fn->gpl_only) {
verbose(env, "cannot call GPL-restricted function from non-GPL compatible program\n");
return -EINVAL;
}
/* With LD_ABS/IND some JITs save/restore skb from r1. */
changes_data = bpf_helper_changes_pkt_data(fn->func);
if (changes_data && fn->arg1_type != ARG_PTR_TO_CTX) {
verbose(env, "kernel subsystem misconfigured func %s#%d: r1 != ctx\n",
func_id_name(func_id), func_id);
return -EINVAL;
}
memset(&meta, 0, sizeof(meta));
meta.pkt_access = fn->pkt_access;
err = check_func_proto(fn, func_id);
if (err) {
verbose(env, "kernel subsystem misconfigured func %s#%d\n",
func_id_name(func_id), func_id);
return err;
}
meta.func_id = func_id;
/* check args */
err = check_func_arg(env, BPF_REG_1, fn->arg1_type, &meta);
if (err)
return err;
err = check_func_arg(env, BPF_REG_2, fn->arg2_type, &meta);
if (err)
return err;
err = check_func_arg(env, BPF_REG_3, fn->arg3_type, &meta);
if (err)
return err;
err = check_func_arg(env, BPF_REG_4, fn->arg4_type, &meta);
if (err)
return err;
err = check_func_arg(env, BPF_REG_5, fn->arg5_type, &meta);
if (err)
return err;
err = record_func_map(env, &meta, func_id, insn_idx);
if (err)
return err;
/* Mark slots with STACK_MISC in case of raw mode, stack offset
* is inferred from register state.
*/
for (i = 0; i < meta.access_size; i++) {
err = check_mem_access(env, insn_idx, meta.regno, i, BPF_B,
BPF_WRITE, -1, false);
if (err)
return err;
}
if (func_id == BPF_FUNC_tail_call) {
err = check_reference_leak(env);
if (err) {
verbose(env, "tail_call would lead to reference leak\n");
return err;
}
} else if (is_release_function(func_id)) {
err = release_reference(env, meta.ref_obj_id);
if (err) {
verbose(env, "func %s#%d reference has not been acquired before\n",
func_id_name(func_id), func_id);
return err;
}
}
regs = cur_regs(env);
/* check that flags argument in get_local_storage(map, flags) is 0,
* this is required because get_local_storage() can't return an error.
*/
if (func_id == BPF_FUNC_get_local_storage &&
!register_is_null(&regs[BPF_REG_2])) {
verbose(env, "get_local_storage() doesn't support non-zero flags\n");
return -EINVAL;
}
/* reset caller saved regs */
for (i = 0; i < CALLER_SAVED_REGS; i++) {
mark_reg_not_init(env, regs, caller_saved[i]);
check_reg_arg(env, caller_saved[i], DST_OP_NO_MARK);
}
/* update return register (already marked as written above) */
if (fn->ret_type == RET_INTEGER) {
/* sets type to SCALAR_VALUE */
mark_reg_unknown(env, regs, BPF_REG_0);
} else if (fn->ret_type == RET_VOID) {
regs[BPF_REG_0].type = NOT_INIT;
} else if (fn->ret_type == RET_PTR_TO_MAP_VALUE_OR_NULL ||
fn->ret_type == RET_PTR_TO_MAP_VALUE) {
/* There is no offset yet applied, variable or fixed */
mark_reg_known_zero(env, regs, BPF_REG_0);
/* remember map_ptr, so that check_map_access()
* can check 'value_size' boundary of memory access
* to map element returned from bpf_map_lookup_elem()
*/
if (meta.map_ptr == NULL) {
verbose(env,
"kernel subsystem misconfigured verifier\n");
return -EINVAL;
}
regs[BPF_REG_0].map_ptr = meta.map_ptr;
if (fn->ret_type == RET_PTR_TO_MAP_VALUE) {
regs[BPF_REG_0].type = PTR_TO_MAP_VALUE;
if (map_value_has_spin_lock(meta.map_ptr))
regs[BPF_REG_0].id = ++env->id_gen;
} else {
regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL;
regs[BPF_REG_0].id = ++env->id_gen;
}
} else if (fn->ret_type == RET_PTR_TO_SOCKET_OR_NULL) {
mark_reg_known_zero(env, regs, BPF_REG_0);
regs[BPF_REG_0].type = PTR_TO_SOCKET_OR_NULL;
if (is_acquire_function(func_id)) {
int id = acquire_reference_state(env, insn_idx);
if (id < 0)
return id;
/* For mark_ptr_or_null_reg() */
regs[BPF_REG_0].id = id;
/* For release_reference() */
regs[BPF_REG_0].ref_obj_id = id;
} else {
/* For mark_ptr_or_null_reg() */
regs[BPF_REG_0].id = ++env->id_gen;
}
} else if (fn->ret_type == RET_PTR_TO_TCP_SOCK_OR_NULL) {
mark_reg_known_zero(env, regs, BPF_REG_0);
regs[BPF_REG_0].type = PTR_TO_TCP_SOCK_OR_NULL;
regs[BPF_REG_0].id = ++env->id_gen;
} else {
verbose(env, "unknown return type %d of func %s#%d\n",
fn->ret_type, func_id_name(func_id), func_id);
return -EINVAL;
}
if (is_ptr_cast_function(func_id))
/* For release_reference() */
regs[BPF_REG_0].ref_obj_id = meta.ref_obj_id;
do_refine_retval_range(regs, fn->ret_type, func_id, &meta);
err = check_map_func_compatibility(env, meta.map_ptr, func_id);
if (err)
return err;
if (func_id == BPF_FUNC_get_stack && !env->prog->has_callchain_buf) {
const char *err_str;
#ifdef CONFIG_PERF_EVENTS
err = get_callchain_buffers(sysctl_perf_event_max_stack);
err_str = "cannot get callchain buffer for func %s#%d\n";
#else
err = -ENOTSUPP;
err_str = "func %s#%d not supported without CONFIG_PERF_EVENTS\n";
#endif
if (err) {
verbose(env, err_str, func_id_name(func_id), func_id);
return err;
}
env->prog->has_callchain_buf = true;
}
if (changes_data)
clear_all_pkt_pointers(env);
return 0;
}
static bool signed_add_overflows(s64 a, s64 b)
{
/* Do the add in u64, where overflow is well-defined */
s64 res = (s64)((u64)a + (u64)b);
if (b < 0)
return res > a;
return res < a;
}
static bool signed_sub_overflows(s64 a, s64 b)
{
/* Do the sub in u64, where overflow is well-defined */
s64 res = (s64)((u64)a - (u64)b);
if (b < 0)
return res < a;
return res > a;
}
static bool check_reg_sane_offset(struct bpf_verifier_env *env,
const struct bpf_reg_state *reg,
enum bpf_reg_type type)
{
bool known = tnum_is_const(reg->var_off);
s64 val = reg->var_off.value;
s64 smin = reg->smin_value;
if (known && (val >= BPF_MAX_VAR_OFF || val <= -BPF_MAX_VAR_OFF)) {
verbose(env, "math between %s pointer and %lld is not allowed\n",
reg_type_str[type], val);
return false;
}
if (reg->off >= BPF_MAX_VAR_OFF || reg->off <= -BPF_MAX_VAR_OFF) {
verbose(env, "%s pointer offset %d is not allowed\n",
reg_type_str[type], reg->off);
return false;
}
if (smin == S64_MIN) {
verbose(env, "math between %s pointer and register with unbounded min value is not allowed\n",
reg_type_str[type]);
return false;
}
if (smin >= BPF_MAX_VAR_OFF || smin <= -BPF_MAX_VAR_OFF) {
verbose(env, "value %lld makes %s pointer be out of bounds\n",
smin, reg_type_str[type]);
return false;
}
return true;
}
static struct bpf_insn_aux_data *cur_aux(struct bpf_verifier_env *env)
{
return &env->insn_aux_data[env->insn_idx];
}
static int retrieve_ptr_limit(const struct bpf_reg_state *ptr_reg,
u32 *ptr_limit, u8 opcode, bool off_is_neg)
{
bool mask_to_left = (opcode == BPF_ADD && off_is_neg) ||
(opcode == BPF_SUB && !off_is_neg);
u32 off;
switch (ptr_reg->type) {
case PTR_TO_STACK:
off = ptr_reg->off + ptr_reg->var_off.value;
if (mask_to_left)
*ptr_limit = MAX_BPF_STACK + off;
else
*ptr_limit = -off;
return 0;
case PTR_TO_MAP_VALUE:
if (mask_to_left) {
*ptr_limit = ptr_reg->umax_value + ptr_reg->off;
} else {
off = ptr_reg->smin_value + ptr_reg->off;
*ptr_limit = ptr_reg->map_ptr->value_size - off;
}
return 0;
default:
return -EINVAL;
}
}
static bool can_skip_alu_sanitation(const struct bpf_verifier_env *env,
const struct bpf_insn *insn)
{
return env->allow_ptr_leaks || BPF_SRC(insn->code) == BPF_K;
}
static int update_alu_sanitation_state(struct bpf_insn_aux_data *aux,
u32 alu_state, u32 alu_limit)
{
/* If we arrived here from different branches with different
* state or limits to sanitize, then this won't work.
*/
if (aux->alu_state &&
(aux->alu_state != alu_state ||
aux->alu_limit != alu_limit))
return -EACCES;
/* Corresponding fixup done in fixup_bpf_calls(). */
aux->alu_state = alu_state;
aux->alu_limit = alu_limit;
return 0;
}
static int sanitize_val_alu(struct bpf_verifier_env *env,
struct bpf_insn *insn)
{
struct bpf_insn_aux_data *aux = cur_aux(env);
if (can_skip_alu_sanitation(env, insn))
return 0;
return update_alu_sanitation_state(aux, BPF_ALU_NON_POINTER, 0);
}
static int sanitize_ptr_alu(struct bpf_verifier_env *env,
struct bpf_insn *insn,
const struct bpf_reg_state *ptr_reg,
struct bpf_reg_state *dst_reg,
bool off_is_neg)
{
struct bpf_verifier_state *vstate = env->cur_state;
struct bpf_insn_aux_data *aux = cur_aux(env);
bool ptr_is_dst_reg = ptr_reg == dst_reg;
u8 opcode = BPF_OP(insn->code);
u32 alu_state, alu_limit;
struct bpf_reg_state tmp;
bool ret;
if (can_skip_alu_sanitation(env, insn))
return 0;
/* We already marked aux for masking from non-speculative
* paths, thus we got here in the first place. We only care
* to explore bad access from here.
*/
if (vstate->speculative)
goto do_sim;
alu_state = off_is_neg ? BPF_ALU_NEG_VALUE : 0;
alu_state |= ptr_is_dst_reg ?
BPF_ALU_SANITIZE_SRC : BPF_ALU_SANITIZE_DST;
if (retrieve_ptr_limit(ptr_reg, &alu_limit, opcode, off_is_neg))
return 0;
if (update_alu_sanitation_state(aux, alu_state, alu_limit))
return -EACCES;
do_sim:
/* Simulate and find potential out-of-bounds access under
* speculative execution from truncation as a result of
* masking when off was not within expected range. If off
* sits in dst, then we temporarily need to move ptr there
* to simulate dst (== 0) +/-= ptr. Needed, for example,
* for cases where we use K-based arithmetic in one direction
* and truncated reg-based in the other in order to explore
* bad access.
*/
if (!ptr_is_dst_reg) {
tmp = *dst_reg;
*dst_reg = *ptr_reg;
}
ret = push_stack(env, env->insn_idx + 1, env->insn_idx, true);
if (!ptr_is_dst_reg && ret)
*dst_reg = tmp;
return !ret ? -EFAULT : 0;
}
/* Handles arithmetic on a pointer and a scalar: computes new min/max and var_off.
* Caller should also handle BPF_MOV case separately.
* If we return -EACCES, caller may want to try again treating pointer as a
* scalar. So we only emit a diagnostic if !env->allow_ptr_leaks.
*/
static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
struct bpf_insn *insn,
const struct bpf_reg_state *ptr_reg,
const struct bpf_reg_state *off_reg)
{
struct bpf_verifier_state *vstate = env->cur_state;
struct bpf_func_state *state = vstate->frame[vstate->curframe];
struct bpf_reg_state *regs = state->regs, *dst_reg;
bool known = tnum_is_const(off_reg->var_off);
s64 smin_val = off_reg->smin_value, smax_val = off_reg->smax_value,
smin_ptr = ptr_reg->smin_value, smax_ptr = ptr_reg->smax_value;
u64 umin_val = off_reg->umin_value, umax_val = off_reg->umax_value,
umin_ptr = ptr_reg->umin_value, umax_ptr = ptr_reg->umax_value;
u32 dst = insn->dst_reg, src = insn->src_reg;
u8 opcode = BPF_OP(insn->code);
int ret;
dst_reg = &regs[dst];
if ((known && (smin_val != smax_val || umin_val != umax_val)) ||
smin_val > smax_val || umin_val > umax_val) {
/* Taint dst register if offset had invalid bounds derived from
* e.g. dead branches.
*/
__mark_reg_unknown(dst_reg);
return 0;
}
if (BPF_CLASS(insn->code) != BPF_ALU64) {
/* 32-bit ALU ops on pointers produce (meaningless) scalars */
verbose(env,
"R%d 32-bit pointer arithmetic prohibited\n",
dst);
return -EACCES;
}
switch (ptr_reg->type) {
case PTR_TO_MAP_VALUE_OR_NULL:
verbose(env, "R%d pointer arithmetic on %s prohibited, null-check it first\n",
dst, reg_type_str[ptr_reg->type]);
return -EACCES;
case CONST_PTR_TO_MAP:
case PTR_TO_PACKET_END:
case PTR_TO_SOCKET:
case PTR_TO_SOCKET_OR_NULL:
case PTR_TO_SOCK_COMMON:
case PTR_TO_SOCK_COMMON_OR_NULL:
case PTR_TO_TCP_SOCK:
case PTR_TO_TCP_SOCK_OR_NULL:
verbose(env, "R%d pointer arithmetic on %s prohibited\n",
dst, reg_type_str[ptr_reg->type]);
return -EACCES;
case PTR_TO_MAP_VALUE:
if (!env->allow_ptr_leaks && !known && (smin_val < 0) != (smax_val < 0)) {
verbose(env, "R%d has unknown scalar with mixed signed bounds, pointer arithmetic with it prohibited for !root\n",
off_reg == dst_reg ? dst : src);
return -EACCES;
}
/* fall-through */
default:
break;
}
/* In case of 'scalar += pointer', dst_reg inherits pointer type and id.
* The id may be overwritten later if we create a new variable offset.
*/
dst_reg->type = ptr_reg->type;
dst_reg->id = ptr_reg->id;
if (!check_reg_sane_offset(env, off_reg, ptr_reg->type) ||
!check_reg_sane_offset(env, ptr_reg, ptr_reg->type))
return -EINVAL;
switch (opcode) {
case BPF_ADD:
ret = sanitize_ptr_alu(env, insn, ptr_reg, dst_reg, smin_val < 0);
if (ret < 0) {
verbose(env, "R%d tried to add from different maps or paths\n", dst);
return ret;
}
/* We can take a fixed offset as long as it doesn't overflow
* the s32 'off' field
*/
if (known && (ptr_reg->off + smin_val ==
(s64)(s32)(ptr_reg->off + smin_val))) {
/* pointer += K. Accumulate it into fixed offset */
dst_reg->smin_value = smin_ptr;
dst_reg->smax_value = smax_ptr;
dst_reg->umin_value = umin_ptr;
dst_reg->umax_value = umax_ptr;
dst_reg->var_off = ptr_reg->var_off;
dst_reg->off = ptr_reg->off + smin_val;
dst_reg->raw = ptr_reg->raw;
break;
}
/* A new variable offset is created. Note that off_reg->off
* == 0, since it's a scalar.
* dst_reg gets the pointer type and since some positive
* integer value was added to the pointer, give it a new 'id'
* if it's a PTR_TO_PACKET.
* this creates a new 'base' pointer, off_reg (variable) gets
* added into the variable offset, and we copy the fixed offset
* from ptr_reg.
*/
if (signed_add_overflows(smin_ptr, smin_val) ||
signed_add_overflows(smax_ptr, smax_val)) {
dst_reg->smin_value = S64_MIN;
dst_reg->smax_value = S64_MAX;
} else {
dst_reg->smin_value = smin_ptr + smin_val;
dst_reg->smax_value = smax_ptr + smax_val;
}
if (umin_ptr + umin_val < umin_ptr ||
umax_ptr + umax_val < umax_ptr) {
dst_reg->umin_value = 0;
dst_reg->umax_value = U64_MAX;
} else {
dst_reg->umin_value = umin_ptr + umin_val;
dst_reg->umax_value = umax_ptr + umax_val;
}
dst_reg->var_off = tnum_add(ptr_reg->var_off, off_reg->var_off);
dst_reg->off = ptr_reg->off;
dst_reg->raw = ptr_reg->raw;
if (reg_is_pkt_pointer(ptr_reg)) {
dst_reg->id = ++env->id_gen;
/* something was added to pkt_ptr, set range to zero */
dst_reg->raw = 0;
}
break;
case BPF_SUB:
ret = sanitize_ptr_alu(env, insn, ptr_reg, dst_reg, smin_val < 0);
if (ret < 0) {
verbose(env, "R%d tried to sub from different maps or paths\n", dst);
return ret;
}
if (dst_reg == off_reg) {
/* scalar -= pointer. Creates an unknown scalar */
verbose(env, "R%d tried to subtract pointer from scalar\n",
dst);
return -EACCES;
}
/* We don't allow subtraction from FP, because (according to
* test_verifier.c test "invalid fp arithmetic", JITs might not
* be able to deal with it.
*/
if (ptr_reg->type == PTR_TO_STACK) {
verbose(env, "R%d subtraction from stack pointer prohibited\n",
dst);
return -EACCES;
}
if (known && (ptr_reg->off - smin_val ==
(s64)(s32)(ptr_reg->off - smin_val))) {
/* pointer -= K. Subtract it from fixed offset */
dst_reg->smin_value = smin_ptr;
dst_reg->smax_value = smax_ptr;
dst_reg->umin_value = umin_ptr;
dst_reg->umax_value = umax_ptr;
dst_reg->var_off = ptr_reg->var_off;
dst_reg->id = ptr_reg->id;
dst_reg->off = ptr_reg->off - smin_val;
dst_reg->raw = ptr_reg->raw;
break;
}
/* A new variable offset is created. If the subtrahend is known
* nonnegative, then any reg->range we had before is still good.
*/
if (signed_sub_overflows(smin_ptr, smax_val) ||
signed_sub_overflows(smax_ptr, smin_val)) {
/* Overflow possible, we know nothing */
dst_reg->smin_value = S64_MIN;
dst_reg->smax_value = S64_MAX;
} else {
dst_reg->smin_value = smin_ptr - smax_val;
dst_reg->smax_value = smax_ptr - smin_val;
}
if (umin_ptr < umax_val) {
/* Overflow possible, we know nothing */
dst_reg->umin_value = 0;
dst_reg->umax_value = U64_MAX;
} else {
/* Cannot overflow (as long as bounds are consistent) */
dst_reg->umin_value = umin_ptr - umax_val;
dst_reg->umax_value = umax_ptr - umin_val;
}
dst_reg->var_off = tnum_sub(ptr_reg->var_off, off_reg->var_off);
dst_reg->off = ptr_reg->off;
dst_reg->raw = ptr_reg->raw;
if (reg_is_pkt_pointer(ptr_reg)) {
dst_reg->id = ++env->id_gen;
/* something was added to pkt_ptr, set range to zero */
if (smin_val < 0)
dst_reg->raw = 0;
}
break;
case BPF_AND:
case BPF_OR:
case BPF_XOR:
/* bitwise ops on pointers are troublesome, prohibit. */
verbose(env, "R%d bitwise operator %s on pointer prohibited\n",
dst, bpf_alu_string[opcode >> 4]);
return -EACCES;
default:
/* other operators (e.g. MUL,LSH) produce non-pointer results */
verbose(env, "R%d pointer arithmetic with %s operator prohibited\n",
dst, bpf_alu_string[opcode >> 4]);
return -EACCES;
}
if (!check_reg_sane_offset(env, dst_reg, ptr_reg->type))
return -EINVAL;
__update_reg_bounds(dst_reg);
__reg_deduce_bounds(dst_reg);
__reg_bound_offset(dst_reg);
/* For unprivileged we require that resulting offset must be in bounds
* in order to be able to sanitize access later on.
*/
if (!env->allow_ptr_leaks) {
if (dst_reg->type == PTR_TO_MAP_VALUE &&
check_map_access(env, dst, dst_reg->off, 1, false)) {
verbose(env, "R%d pointer arithmetic of map value goes out of range, "
"prohibited for !root\n", dst);
return -EACCES;
} else if (dst_reg->type == PTR_TO_STACK &&
check_stack_access(env, dst_reg, dst_reg->off +
dst_reg->var_off.value, 1)) {
verbose(env, "R%d stack pointer arithmetic goes out of range, "
"prohibited for !root\n", dst);
return -EACCES;
}
}
return 0;
}
/* WARNING: This function does calculations on 64-bit values, but the actual
* execution may occur on 32-bit values. Therefore, things like bitshifts
* need extra checks in the 32-bit case.
*/
static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env,
struct bpf_insn *insn,
struct bpf_reg_state *dst_reg,
struct bpf_reg_state src_reg)
{
struct bpf_reg_state *regs = cur_regs(env);
u8 opcode = BPF_OP(insn->code);
bool src_known, dst_known;
s64 smin_val, smax_val;
u64 umin_val, umax_val;
u64 insn_bitness = (BPF_CLASS(insn->code) == BPF_ALU64) ? 64 : 32;
u32 dst = insn->dst_reg;
int ret;
if (insn_bitness == 32) {
/* Relevant for 32-bit RSH: Information can propagate towards
* LSB, so it isn't sufficient to only truncate the output to
* 32 bits.
*/
coerce_reg_to_size(dst_reg, 4);
coerce_reg_to_size(&src_reg, 4);
}
smin_val = src_reg.smin_value;
smax_val = src_reg.smax_value;
umin_val = src_reg.umin_value;
umax_val = src_reg.umax_value;
src_known = tnum_is_const(src_reg.var_off);
dst_known = tnum_is_const(dst_reg->var_off);
if ((src_known && (smin_val != smax_val || umin_val != umax_val)) ||
smin_val > smax_val || umin_val > umax_val) {
/* Taint dst register if offset had invalid bounds derived from
* e.g. dead branches.
*/
__mark_reg_unknown(dst_reg);
return 0;
}
if (!src_known &&
opcode != BPF_ADD && opcode != BPF_SUB && opcode != BPF_AND) {
__mark_reg_unknown(dst_reg);
return 0;
}
switch (opcode) {
case BPF_ADD:
ret = sanitize_val_alu(env, insn);
if (ret < 0) {
verbose(env, "R%d tried to add from different pointers or scalars\n", dst);
return ret;
}
if (signed_add_overflows(dst_reg->smin_value, smin_val) ||
signed_add_overflows(dst_reg->smax_value, smax_val)) {
dst_reg->smin_value = S64_MIN;
dst_reg->smax_value = S64_MAX;
} else {
dst_reg->smin_value += smin_val;
dst_reg->smax_value += smax_val;
}
if (dst_reg->umin_value + umin_val < umin_val ||
dst_reg->umax_value + umax_val < umax_val) {
dst_reg->umin_value = 0;
dst_reg->umax_value = U64_MAX;
} else {
dst_reg->umin_value += umin_val;
dst_reg->umax_value += umax_val;
}
dst_reg->var_off = tnum_add(dst_reg->var_off, src_reg.var_off);
break;
case BPF_SUB:
ret = sanitize_val_alu(env, insn);
if (ret < 0) {
verbose(env, "R%d tried to sub from different pointers or scalars\n", dst);
return ret;
}
if (signed_sub_overflows(dst_reg->smin_value, smax_val) ||
signed_sub_overflows(dst_reg->smax_value, smin_val)) {
/* Overflow possible, we know nothing */
dst_reg->smin_value = S64_MIN;
dst_reg->smax_value = S64_MAX;
} else {
dst_reg->smin_value -= smax_val;
dst_reg->smax_value -= smin_val;
}
if (dst_reg->umin_value < umax_val) {
/* Overflow possible, we know nothing */
dst_reg->umin_value = 0;
dst_reg->umax_value = U64_MAX;
} else {
/* Cannot overflow (as long as bounds are consistent) */
dst_reg->umin_value -= umax_val;
dst_reg->umax_value -= umin_val;
}
dst_reg->var_off = tnum_sub(dst_reg->var_off, src_reg.var_off);
break;
case BPF_MUL:
dst_reg->var_off = tnum_mul(dst_reg->var_off, src_reg.var_off);
if (smin_val < 0 || dst_reg->smin_value < 0) {
/* Ain't nobody got time to multiply that sign */
__mark_reg_unbounded(dst_reg);
__update_reg_bounds(dst_reg);
break;
}
/* Both values are positive, so we can work with unsigned and
* copy the result to signed (unless it exceeds S64_MAX).
*/
if (umax_val > U32_MAX || dst_reg->umax_value > U32_MAX) {
/* Potential overflow, we know nothing */
__mark_reg_unbounded(dst_reg);
/* (except what we can learn from the var_off) */
__update_reg_bounds(dst_reg);
break;
}
dst_reg->umin_value *= umin_val;
dst_reg->umax_value *= umax_val;
if (dst_reg->umax_value > S64_MAX) {
/* Overflow possible, we know nothing */
dst_reg->smin_value = S64_MIN;
dst_reg->smax_value = S64_MAX;
} else {
dst_reg->smin_value = dst_reg->umin_value;
dst_reg->smax_value = dst_reg->umax_value;
}
break;
case BPF_AND:
if (src_known && dst_known) {
__mark_reg_known(dst_reg, dst_reg->var_off.value &
src_reg.var_off.value);
break;
}
/* We get our minimum from the var_off, since that's inherently
* bitwise. Our maximum is the minimum of the operands' maxima.
*/
dst_reg->var_off = tnum_and(dst_reg->var_off, src_reg.var_off);
dst_reg->umin_value = dst_reg->var_off.value;
dst_reg->umax_value = min(dst_reg->umax_value, umax_val);
if (dst_reg->smin_value < 0 || smin_val < 0) {
/* Lose signed bounds when ANDing negative numbers,
* ain't nobody got time for that.
*/
dst_reg->smin_value = S64_MIN;
dst_reg->smax_value = S64_MAX;
} else {
/* ANDing two positives gives a positive, so safe to
* cast result into s64.
*/
dst_reg->smin_value = dst_reg->umin_value;
dst_reg->smax_value = dst_reg->umax_value;
}
/* We may learn something more from the var_off */
__update_reg_bounds(dst_reg);
break;
case BPF_OR:
if (src_known && dst_known) {
__mark_reg_known(dst_reg, dst_reg->var_off.value |
src_reg.var_off.value);
break;
}
/* We get our maximum from the var_off, and our minimum is the
* maximum of the operands' minima
*/
dst_reg->var_off = tnum_or(dst_reg->var_off, src_reg.var_off);
dst_reg->umin_value = max(dst_reg->umin_value, umin_val);
dst_reg->umax_value = dst_reg->var_off.value |
dst_reg->var_off.mask;
if (dst_reg->smin_value < 0 || smin_val < 0) {
/* Lose signed bounds when ORing negative numbers,
* ain't nobody got time for that.
*/
dst_reg->smin_value = S64_MIN;
dst_reg->smax_value = S64_MAX;
} else {
/* ORing two positives gives a positive, so safe to
* cast result into s64.
*/
dst_reg->smin_value = dst_reg->umin_value;
dst_reg->smax_value = dst_reg->umax_value;
}
/* We may learn something more from the var_off */
__update_reg_bounds(dst_reg);
break;
case BPF_LSH:
if (umax_val >= insn_bitness) {
/* Shifts greater than 31 or 63 are undefined.
* This includes shifts by a negative number.
*/
mark_reg_unknown(env, regs, insn->dst_reg);
break;
}
/* We lose all sign bit information (except what we can pick
* up from var_off)
*/
dst_reg->smin_value = S64_MIN;
dst_reg->smax_value = S64_MAX;
/* If we might shift our top bit out, then we know nothing */
if (dst_reg->umax_value > 1ULL << (63 - umax_val)) {
dst_reg->umin_value = 0;
dst_reg->umax_value = U64_MAX;
} else {
dst_reg->umin_value <<= umin_val;
dst_reg->umax_value <<= umax_val;
}
dst_reg->var_off = tnum_lshift(dst_reg->var_off, umin_val);
/* We may learn something more from the var_off */
__update_reg_bounds(dst_reg);
break;
case BPF_RSH:
if (umax_val >= insn_bitness) {
/* Shifts greater than 31 or 63 are undefined.
* This includes shifts by a negative number.
*/
mark_reg_unknown(env, regs, insn->dst_reg);
break;
}
/* BPF_RSH is an unsigned shift. If the value in dst_reg might
* be negative, then either:
* 1) src_reg might be zero, so the sign bit of the result is
* unknown, so we lose our signed bounds
* 2) it's known negative, thus the unsigned bounds capture the
* signed bounds
* 3) the signed bounds cross zero, so they tell us nothing
* about the result
* If the value in dst_reg is known nonnegative, then again the
* unsigned bounts capture the signed bounds.
* Thus, in all cases it suffices to blow away our signed bounds
* and rely on inferring new ones from the unsigned bounds and
* var_off of the result.
*/
dst_reg->smin_value = S64_MIN;
dst_reg->smax_value = S64_MAX;
dst_reg->var_off = tnum_rshift(dst_reg->var_off, umin_val);
dst_reg->umin_value >>= umax_val;
dst_reg->umax_value >>= umin_val;
/* We may learn something more from the var_off */
__update_reg_bounds(dst_reg);
break;
case BPF_ARSH:
if (umax_val >= insn_bitness) {
/* Shifts greater than 31 or 63 are undefined.
* This includes shifts by a negative number.
*/
mark_reg_unknown(env, regs, insn->dst_reg);
break;
}
/* Upon reaching here, src_known is true and
* umax_val is equal to umin_val.
*/
dst_reg->smin_value >>= umin_val;
dst_reg->smax_value >>= umin_val;
dst_reg->var_off = tnum_arshift(dst_reg->var_off, umin_val);
/* blow away the dst_reg umin_value/umax_value and rely on
* dst_reg var_off to refine the result.
*/
dst_reg->umin_value = 0;
dst_reg->umax_value = U64_MAX;
__update_reg_bounds(dst_reg);
break;
default:
mark_reg_unknown(env, regs, insn->dst_reg);
break;
}
if (BPF_CLASS(insn->code) != BPF_ALU64) {
/* 32-bit ALU ops are (32,32)->32 */
coerce_reg_to_size(dst_reg, 4);
}
__reg_deduce_bounds(dst_reg);
__reg_bound_offset(dst_reg);
return 0;
}
/* Handles ALU ops other than BPF_END, BPF_NEG and BPF_MOV: computes new min/max
* and var_off.
*/
static int adjust_reg_min_max_vals(struct bpf_verifier_env *env,
struct bpf_insn *insn)
{
struct bpf_verifier_state *vstate = env->cur_state;
struct bpf_func_state *state = vstate->frame[vstate->curframe];
struct bpf_reg_state *regs = state->regs, *dst_reg, *src_reg;
struct bpf_reg_state *ptr_reg = NULL, off_reg = {0};
u8 opcode = BPF_OP(insn->code);
dst_reg = &regs[insn->dst_reg];
src_reg = NULL;
if (dst_reg->type != SCALAR_VALUE)
ptr_reg = dst_reg;
if (BPF_SRC(insn->code) == BPF_X) {
src_reg = &regs[insn->src_reg];
if (src_reg->type != SCALAR_VALUE) {
if (dst_reg->type != SCALAR_VALUE) {
/* Combining two pointers by any ALU op yields
* an arbitrary scalar. Disallow all math except
* pointer subtraction
*/
if (opcode == BPF_SUB && env->allow_ptr_leaks) {
mark_reg_unknown(env, regs, insn->dst_reg);
return 0;
}
verbose(env, "R%d pointer %s pointer prohibited\n",
insn->dst_reg,
bpf_alu_string[opcode >> 4]);
return -EACCES;
} else {
/* scalar += pointer
* This is legal, but we have to reverse our
* src/dest handling in computing the range
*/
return adjust_ptr_min_max_vals(env, insn,
src_reg, dst_reg);
}
} else if (ptr_reg) {
/* pointer += scalar */
return adjust_ptr_min_max_vals(env, insn,
dst_reg, src_reg);
}
} else {
/* Pretend the src is a reg with a known value, since we only
* need to be able to read from this state.
*/
off_reg.type = SCALAR_VALUE;
__mark_reg_known(&off_reg, insn->imm);
src_reg = &off_reg;
if (ptr_reg) /* pointer += K */
return adjust_ptr_min_max_vals(env, insn,
ptr_reg, src_reg);
}
/* Got here implies adding two SCALAR_VALUEs */
if (WARN_ON_ONCE(ptr_reg)) {
print_verifier_state(env, state);
verbose(env, "verifier internal error: unexpected ptr_reg\n");
return -EINVAL;
}
if (WARN_ON(!src_reg)) {
print_verifier_state(env, state);
verbose(env, "verifier internal error: no src_reg\n");
return -EINVAL;
}
return adjust_scalar_min_max_vals(env, insn, dst_reg, *src_reg);
}
/* check validity of 32-bit and 64-bit arithmetic operations */
static int check_alu_op(struct bpf_verifier_env *env, struct bpf_insn *insn)
{
struct bpf_reg_state *regs = cur_regs(env);
u8 opcode = BPF_OP(insn->code);
int err;
if (opcode == BPF_END || opcode == BPF_NEG) {
if (opcode == BPF_NEG) {
if (BPF_SRC(insn->code) != 0 ||
insn->src_reg != BPF_REG_0 ||
insn->off != 0 || insn->imm != 0) {
verbose(env, "BPF_NEG uses reserved fields\n");
return -EINVAL;
}
} else {
if (insn->src_reg != BPF_REG_0 || insn->off != 0 ||
(insn->imm != 16 && insn->imm != 32 && insn->imm != 64) ||
BPF_CLASS(insn->code) == BPF_ALU64) {
verbose(env, "BPF_END uses reserved fields\n");
return -EINVAL;
}
}
/* check src operand */
err = check_reg_arg(env, insn->dst_reg, SRC_OP);
if (err)
return err;
if (is_pointer_value(env, insn->dst_reg)) {
verbose(env, "R%d pointer arithmetic prohibited\n",
insn->dst_reg);
return -EACCES;
}
/* check dest operand */
err = check_reg_arg(env, insn->dst_reg, DST_OP);
if (err)
return err;
} else if (opcode == BPF_MOV) {
if (BPF_SRC(insn->code) == BPF_X) {
if (insn->imm != 0 || insn->off != 0) {
verbose(env, "BPF_MOV uses reserved fields\n");
return -EINVAL;
}
/* check src operand */
err = check_reg_arg(env, insn->src_reg, SRC_OP);
if (err)
return err;
} else {
if (insn->src_reg != BPF_REG_0 || insn->off != 0) {
verbose(env, "BPF_MOV uses reserved fields\n");
return -EINVAL;
}
}
/* check dest operand, mark as required later */
err = check_reg_arg(env, insn->dst_reg, DST_OP_NO_MARK);
if (err)
return err;
if (BPF_SRC(insn->code) == BPF_X) {
struct bpf_reg_state *src_reg = regs + insn->src_reg;
struct bpf_reg_state *dst_reg = regs + insn->dst_reg;
if (BPF_CLASS(insn->code) == BPF_ALU64) {
/* case: R1 = R2
* copy register state to dest reg
*/
*dst_reg = *src_reg;
dst_reg->live |= REG_LIVE_WRITTEN;
} else {
/* R1 = (u32) R2 */
if (is_pointer_value(env, insn->src_reg)) {
verbose(env,
"R%d partial copy of pointer\n",
insn->src_reg);
return -EACCES;
} else if (src_reg->type == SCALAR_VALUE) {
*dst_reg = *src_reg;
dst_reg->live |= REG_LIVE_WRITTEN;
} else {
mark_reg_unknown(env, regs,
insn->dst_reg);
}
coerce_reg_to_size(dst_reg, 4);
}
} else {
/* case: R = imm
* remember the value we stored into this reg
*/
/* clear any state __mark_reg_known doesn't set */
mark_reg_unknown(env, regs, insn->dst_reg);
regs[insn->dst_reg].type = SCALAR_VALUE;
if (BPF_CLASS(insn->code) == BPF_ALU64) {
__mark_reg_known(regs + insn->dst_reg,
insn->imm);
} else {
__mark_reg_known(regs + insn->dst_reg,
(u32)insn->imm);
}
}
} else if (opcode > BPF_END) {
verbose(env, "invalid BPF_ALU opcode %x\n", opcode);
return -EINVAL;
} else { /* all other ALU ops: and, sub, xor, add, ... */
if (BPF_SRC(insn->code) == BPF_X) {
if (insn->imm != 0 || insn->off != 0) {
verbose(env, "BPF_ALU uses reserved fields\n");
return -EINVAL;
}
/* check src1 operand */
err = check_reg_arg(env, insn->src_reg, SRC_OP);
if (err)
return err;
} else {
if (insn->src_reg != BPF_REG_0 || insn->off != 0) {
verbose(env, "BPF_ALU uses reserved fields\n");
return -EINVAL;
}
}
/* check src2 operand */
err = check_reg_arg(env, insn->dst_reg, SRC_OP);
if (err)
return err;
if ((opcode == BPF_MOD || opcode == BPF_DIV) &&
BPF_SRC(insn->code) == BPF_K && insn->imm == 0) {
verbose(env, "div by zero\n");
return -EINVAL;
}
if ((opcode == BPF_LSH || opcode == BPF_RSH ||
opcode == BPF_ARSH) && BPF_SRC(insn->code) == BPF_K) {
int size = BPF_CLASS(insn->code) == BPF_ALU64 ? 64 : 32;
if (insn->imm < 0 || insn->imm >= size) {
verbose(env, "invalid shift %d\n", insn->imm);
return -EINVAL;
}
}
/* check dest operand */
err = check_reg_arg(env, insn->dst_reg, DST_OP_NO_MARK);
if (err)
return err;
return adjust_reg_min_max_vals(env, insn);
}
return 0;
}
static void find_good_pkt_pointers(struct bpf_verifier_state *vstate,
struct bpf_reg_state *dst_reg,
enum bpf_reg_type type,
bool range_right_open)
{
struct bpf_func_state *state = vstate->frame[vstate->curframe];
struct bpf_reg_state *regs = state->regs, *reg;
u16 new_range;
int i, j;
if (dst_reg->off < 0 ||
(dst_reg->off == 0 && range_right_open))
/* This doesn't give us any range */
return;
if (dst_reg->umax_value > MAX_PACKET_OFF ||
dst_reg->umax_value + dst_reg->off > MAX_PACKET_OFF)
/* Risk of overflow. For instance, ptr + (1<<63) may be less
* than pkt_end, but that's because it's also less than pkt.
*/
return;
new_range = dst_reg->off;
if (range_right_open)
new_range--;
/* Examples for register markings:
*
* pkt_data in dst register:
*
* r2 = r3;
* r2 += 8;
* if (r2 > pkt_end) goto <handle exception>
* <access okay>
*
* r2 = r3;
* r2 += 8;
* if (r2 < pkt_end) goto <access okay>
* <handle exception>
*
* Where:
* r2 == dst_reg, pkt_end == src_reg
* r2=pkt(id=n,off=8,r=0)
* r3=pkt(id=n,off=0,r=0)
*
* pkt_data in src register:
*
* r2 = r3;
* r2 += 8;
* if (pkt_end >= r2) goto <access okay>
* <handle exception>
*
* r2 = r3;
* r2 += 8;
* if (pkt_end <= r2) goto <handle exception>
* <access okay>
*
* Where:
* pkt_end == dst_reg, r2 == src_reg
* r2=pkt(id=n,off=8,r=0)
* r3=pkt(id=n,off=0,r=0)
*
* Find register r3 and mark its range as r3=pkt(id=n,off=0,r=8)
* or r3=pkt(id=n,off=0,r=8-1), so that range of bytes [r3, r3 + 8)
* and [r3, r3 + 8-1) respectively is safe to access depending on
* the check.
*/
/* If our ids match, then we must have the same max_value. And we
* don't care about the other reg's fixed offset, since if it's too big
* the range won't allow anything.
* dst_reg->off is known < MAX_PACKET_OFF, therefore it fits in a u16.
*/
for (i = 0; i < MAX_BPF_REG; i++)
if (regs[i].type == type && regs[i].id == dst_reg->id)
/* keep the maximum range already checked */
regs[i].range = max(regs[i].range, new_range);
for (j = 0; j <= vstate->curframe; j++) {
state = vstate->frame[j];
bpf_for_each_spilled_reg(i, state, reg) {
if (!reg)
continue;
if (reg->type == type && reg->id == dst_reg->id)
reg->range = max(reg->range, new_range);
}
}
}
/* compute branch direction of the expression "if (reg opcode val) goto target;"
* and return:
* 1 - branch will be taken and "goto target" will be executed
* 0 - branch will not be taken and fall-through to next insn
* -1 - unknown. Example: "if (reg < 5)" is unknown when register value range [0,10]
*/
static int is_branch_taken(struct bpf_reg_state *reg, u64 val, u8 opcode,
bool is_jmp32)
{
struct bpf_reg_state reg_lo;
s64 sval;
if (__is_pointer_value(false, reg))
return -1;
if (is_jmp32) {
reg_lo = *reg;
reg = &reg_lo;
/* For JMP32, only low 32 bits are compared, coerce_reg_to_size
* could truncate high bits and update umin/umax according to
* information of low bits.
*/
coerce_reg_to_size(reg, 4);
/* smin/smax need special handling. For example, after coerce,
* if smin_value is 0x00000000ffffffffLL, the value is -1 when
* used as operand to JMP32. It is a negative number from s32's
* point of view, while it is a positive number when seen as
* s64. The smin/smax are kept as s64, therefore, when used with
* JMP32, they need to be transformed into s32, then sign
* extended back to s64.
*
* Also, smin/smax were copied from umin/umax. If umin/umax has
* different sign bit, then min/max relationship doesn't
* maintain after casting into s32, for this case, set smin/smax
* to safest range.
*/
if ((reg->umax_value ^ reg->umin_value) &
(1ULL << 31)) {
reg->smin_value = S32_MIN;
reg->smax_value = S32_MAX;
}
reg->smin_value = (s64)(s32)reg->smin_value;
reg->smax_value = (s64)(s32)reg->smax_value;
val = (u32)val;
sval = (s64)(s32)val;
} else {
sval = (s64)val;
}
switch (opcode) {
case BPF_JEQ:
if (tnum_is_const(reg->var_off))
return !!tnum_equals_const(reg->var_off, val);
break;
case BPF_JNE:
if (tnum_is_const(reg->var_off))
return !tnum_equals_const(reg->var_off, val);
break;
case BPF_JSET:
if ((~reg->var_off.mask & reg->var_off.value) & val)
return 1;
if (!((reg->var_off.mask | reg->var_off.value) & val))
return 0;
break;
case BPF_JGT:
if (reg->umin_value > val)
return 1;
else if (reg->umax_value <= val)
return 0;
break;
case BPF_JSGT:
if (reg->smin_value > sval)
return 1;
else if (reg->smax_value < sval)
return 0;
break;
case BPF_JLT:
if (reg->umax_value < val)
return 1;
else if (reg->umin_value >= val)
return 0;
break;
case BPF_JSLT:
if (reg->smax_value < sval)
return 1;
else if (reg->smin_value >= sval)
return 0;
break;
case BPF_JGE:
if (reg->umin_value >= val)
return 1;
else if (reg->umax_value < val)
return 0;
break;
case BPF_JSGE:
if (reg->smin_value >= sval)
return 1;
else if (reg->smax_value < sval)
return 0;
break;
case BPF_JLE:
if (reg->umax_value <= val)
return 1;
else if (reg->umin_value > val)
return 0;
break;
case BPF_JSLE:
if (reg->smax_value <= sval)
return 1;
else if (reg->smin_value > sval)
return 0;
break;
}
return -1;
}
/* Generate min value of the high 32-bit from TNUM info. */
static u64 gen_hi_min(struct tnum var)
{
return var.value & ~0xffffffffULL;
}
/* Generate max value of the high 32-bit from TNUM info. */
static u64 gen_hi_max(struct tnum var)
{
return (var.value | var.mask) & ~0xffffffffULL;
}
/* Return true if VAL is compared with a s64 sign extended from s32, and they
* are with the same signedness.
*/
static bool cmp_val_with_extended_s64(s64 sval, struct bpf_reg_state *reg)
{
return ((s32)sval >= 0 &&
reg->smin_value >= 0 && reg->smax_value <= S32_MAX) ||
((s32)sval < 0 &&
reg->smax_value <= 0 && reg->smin_value >= S32_MIN);
}
/* Adjusts the register min/max values in the case that the dst_reg is the
* variable register that we are working on, and src_reg is a constant or we're
* simply doing a BPF_K check.
* In JEQ/JNE cases we also adjust the var_off values.
*/
static void reg_set_min_max(struct bpf_reg_state *true_reg,
struct bpf_reg_state *false_reg, u64 val,
u8 opcode, bool is_jmp32)
{
s64 sval;
/* If the dst_reg is a pointer, we can't learn anything about its
* variable offset from the compare (unless src_reg were a pointer into
* the same object, but we don't bother with that.
* Since false_reg and true_reg have the same type by construction, we
* only need to check one of them for pointerness.
*/
if (__is_pointer_value(false, false_reg))
return;
val = is_jmp32 ? (u32)val : val;
sval = is_jmp32 ? (s64)(s32)val : (s64)val;
switch (opcode) {
case BPF_JEQ:
case BPF_JNE:
{
struct bpf_reg_state *reg =
opcode == BPF_JEQ ? true_reg : false_reg;
/* For BPF_JEQ, if this is false we know nothing Jon Snow, but
* if it is true we know the value for sure. Likewise for
* BPF_JNE.
*/
if (is_jmp32) {
u64 old_v = reg->var_off.value;
u64 hi_mask = ~0xffffffffULL;
reg->var_off.value = (old_v & hi_mask) | val;
reg->var_off.mask &= hi_mask;
} else {
__mark_reg_known(reg, val);
}
break;
}
case BPF_JSET:
false_reg->var_off = tnum_and(false_reg->var_off,
tnum_const(~val));
if (is_power_of_2(val))
true_reg->var_off = tnum_or(true_reg->var_off,
tnum_const(val));
break;
case BPF_JGE:
case BPF_JGT:
{
u64 false_umax = opcode == BPF_JGT ? val : val - 1;
u64 true_umin = opcode == BPF_JGT ? val + 1 : val;
if (is_jmp32) {
false_umax += gen_hi_max(false_reg->var_off);
true_umin += gen_hi_min(true_reg->var_off);
}
false_reg->umax_value = min(false_reg->umax_value, false_umax);
true_reg->umin_value = max(true_reg->umin_value, true_umin);
break;
}
case BPF_JSGE:
case BPF_JSGT:
{
s64 false_smax = opcode == BPF_JSGT ? sval : sval - 1;
s64 true_smin = opcode == BPF_JSGT ? sval + 1 : sval;
/* If the full s64 was not sign-extended from s32 then don't
* deduct further info.
*/
if (is_jmp32 && !cmp_val_with_extended_s64(sval, false_reg))
break;
false_reg->smax_value = min(false_reg->smax_value, false_smax);
true_reg->smin_value = max(true_reg->smin_value, true_smin);
break;
}
case BPF_JLE:
case BPF_JLT:
{
u64 false_umin = opcode == BPF_JLT ? val : val + 1;
u64 true_umax = opcode == BPF_JLT ? val - 1 : val;
if (is_jmp32) {
false_umin += gen_hi_min(false_reg->var_off);
true_umax += gen_hi_max(true_reg->var_off);
}
false_reg->umin_value = max(false_reg->umin_value, false_umin);
true_reg->umax_value = min(true_reg->umax_value, true_umax);
break;
}
case BPF_JSLE:
case BPF_JSLT:
{
s64 false_smin = opcode == BPF_JSLT ? sval : sval + 1;
s64 true_smax = opcode == BPF_JSLT ? sval - 1 : sval;
if (is_jmp32 && !cmp_val_with_extended_s64(sval, false_reg))
break;
false_reg->smin_value = max(false_reg->smin_value, false_smin);
true_reg->smax_value = min(true_reg->smax_value, true_smax);
break;
}
default:
break;
}
__reg_deduce_bounds(false_reg);
__reg_deduce_bounds(true_reg);
/* We might have learned some bits from the bounds. */
__reg_bound_offset(false_reg);
__reg_bound_offset(true_reg);
/* Intersecting with the old var_off might have improved our bounds
* slightly. e.g. if umax was 0x7f...f and var_off was (0; 0xf...fc),
* then new var_off is (0; 0x7f...fc) which improves our umax.
*/
__update_reg_bounds(false_reg);
__update_reg_bounds(true_reg);
}
/* Same as above, but for the case that dst_reg holds a constant and src_reg is
* the variable reg.
*/
static void reg_set_min_max_inv(struct bpf_reg_state *true_reg,
struct bpf_reg_state *false_reg, u64 val,
u8 opcode, bool is_jmp32)
{
s64 sval;
if (__is_pointer_value(false, false_reg))
return;
val = is_jmp32 ? (u32)val : val;
sval = is_jmp32 ? (s64)(s32)val : (s64)val;
switch (opcode) {
case BPF_JEQ:
case BPF_JNE:
{
struct bpf_reg_state *reg =
opcode == BPF_JEQ ? true_reg : false_reg;
if (is_jmp32) {
u64 old_v = reg->var_off.value;
u64 hi_mask = ~0xffffffffULL;
reg->var_off.value = (old_v & hi_mask) | val;
reg->var_off.mask &= hi_mask;
} else {
__mark_reg_known(reg, val);
}
break;
}
case BPF_JSET:
false_reg->var_off = tnum_and(false_reg->var_off,
tnum_const(~val));
if (is_power_of_2(val))
true_reg->var_off = tnum_or(true_reg->var_off,
tnum_const(val));
break;
case BPF_JGE:
case BPF_JGT:
{
u64 false_umin = opcode == BPF_JGT ? val : val + 1;
u64 true_umax = opcode == BPF_JGT ? val - 1 : val;
if (is_jmp32) {
false_umin += gen_hi_min(false_reg->var_off);
true_umax += gen_hi_max(true_reg->var_off);
}
false_reg->umin_value = max(false_reg->umin_value, false_umin);
true_reg->umax_value = min(true_reg->umax_value, true_umax);
break;
}
case BPF_JSGE:
case BPF_JSGT:
{
s64 false_smin = opcode == BPF_JSGT ? sval : sval + 1;
s64 true_smax = opcode == BPF_JSGT ? sval - 1 : sval;
if (is_jmp32 && !cmp_val_with_extended_s64(sval, false_reg))
break;
false_reg->smin_value = max(false_reg->smin_value, false_smin);
true_reg->smax_value = min(true_reg->smax_value, true_smax);
break;
}
case BPF_JLE:
case BPF_JLT:
{
u64 false_umax = opcode == BPF_JLT ? val : val - 1;
u64 true_umin = opcode == BPF_JLT ? val + 1 : val;
if (is_jmp32) {
false_umax += gen_hi_max(false_reg->var_off);
true_umin += gen_hi_min(true_reg->var_off);
}
false_reg->umax_value = min(false_reg->umax_value, false_umax);
true_reg->umin_value = max(true_reg->umin_value, true_umin);
break;
}
case BPF_JSLE:
case BPF_JSLT:
{
s64 false_smax = opcode == BPF_JSLT ? sval : sval - 1;
s64 true_smin = opcode == BPF_JSLT ? sval + 1 : sval;
if (is_jmp32 && !cmp_val_with_extended_s64(sval, false_reg))
break;
false_reg->smax_value = min(false_reg->smax_value, false_smax);
true_reg->smin_value = max(true_reg->smin_value, true_smin);
break;
}
default:
break;
}
__reg_deduce_bounds(false_reg);
__reg_deduce_bounds(true_reg);
/* We might have learned some bits from the bounds. */
__reg_bound_offset(false_reg);
__reg_bound_offset(true_reg);
/* Intersecting with the old var_off might have improved our bounds
* slightly. e.g. if umax was 0x7f...f and var_off was (0; 0xf...fc),
* then new var_off is (0; 0x7f...fc) which improves our umax.
*/
__update_reg_bounds(false_reg);
__update_reg_bounds(true_reg);
}
/* Regs are known to be equal, so intersect their min/max/var_off */
static void __reg_combine_min_max(struct bpf_reg_state *src_reg,
struct bpf_reg_state *dst_reg)
{
src_reg->umin_value = dst_reg->umin_value = max(src_reg->umin_value,
dst_reg->umin_value);
src_reg->umax_value = dst_reg->umax_value = min(src_reg->umax_value,
dst_reg->umax_value);
src_reg->smin_value = dst_reg->smin_value = max(src_reg->smin_value,
dst_reg->smin_value);
src_reg->smax_value = dst_reg->smax_value = min(src_reg->smax_value,
dst_reg->smax_value);
src_reg->var_off = dst_reg->var_off = tnum_intersect(src_reg->var_off,
dst_reg->var_off);
/* We might have learned new bounds from the var_off. */
__update_reg_bounds(src_reg);
__update_reg_bounds(dst_reg);
/* We might have learned something about the sign bit. */
__reg_deduce_bounds(src_reg);
__reg_deduce_bounds(dst_reg);
/* We might have learned some bits from the bounds. */
__reg_bound_offset(src_reg);
__reg_bound_offset(dst_reg);
/* Intersecting with the old var_off might have improved our bounds
* slightly. e.g. if umax was 0x7f...f and var_off was (0; 0xf...fc),
* then new var_off is (0; 0x7f...fc) which improves our umax.
*/
__update_reg_bounds(src_reg);
__update_reg_bounds(dst_reg);
}
static void reg_combine_min_max(struct bpf_reg_state *true_src,
struct bpf_reg_state *true_dst,
struct bpf_reg_state *false_src,
struct bpf_reg_state *false_dst,
u8 opcode)
{
switch (opcode) {
case BPF_JEQ:
__reg_combine_min_max(true_src, true_dst);
break;
case BPF_JNE:
__reg_combine_min_max(false_src, false_dst);
break;
}
}
static void mark_ptr_or_null_reg(struct bpf_func_state *state,
struct bpf_reg_state *reg, u32 id,
bool is_null)
{
if (reg_type_may_be_null(reg->type) && reg->id == id) {
/* Old offset (both fixed and variable parts) should
* have been known-zero, because we don't allow pointer
* arithmetic on pointers that might be NULL.
*/
if (WARN_ON_ONCE(reg->smin_value || reg->smax_value ||
!tnum_equals_const(reg->var_off, 0) ||
reg->off)) {
__mark_reg_known_zero(reg);
reg->off = 0;
}
if (is_null) {
reg->type = SCALAR_VALUE;
} else if (reg->type == PTR_TO_MAP_VALUE_OR_NULL) {
if (reg->map_ptr->inner_map_meta) {
reg->type = CONST_PTR_TO_MAP;
reg->map_ptr = reg->map_ptr->inner_map_meta;
} else {
reg->type = PTR_TO_MAP_VALUE;
}
} else if (reg->type == PTR_TO_SOCKET_OR_NULL) {
reg->type = PTR_TO_SOCKET;
} else if (reg->type == PTR_TO_SOCK_COMMON_OR_NULL) {
reg->type = PTR_TO_SOCK_COMMON;
} else if (reg->type == PTR_TO_TCP_SOCK_OR_NULL) {
reg->type = PTR_TO_TCP_SOCK;
}
if (is_null) {
/* We don't need id and ref_obj_id from this point
* onwards anymore, thus we should better reset it,
* so that state pruning has chances to take effect.
*/
reg->id = 0;
reg->ref_obj_id = 0;
} else if (!reg_may_point_to_spin_lock(reg)) {
/* For not-NULL ptr, reg->ref_obj_id will be reset
* in release_reg_references().
*
* reg->id is still used by spin_lock ptr. Other
* than spin_lock ptr type, reg->id can be reset.
*/
reg->id = 0;
}
}
}
/* The logic is similar to find_good_pkt_pointers(), both could eventually
* be folded together at some point.
*/
static void mark_ptr_or_null_regs(struct bpf_verifier_state *vstate, u32 regno,
bool is_null)
{
struct bpf_func_state *state = vstate->frame[vstate->curframe];
struct bpf_reg_state *reg, *regs = state->regs;
u32 ref_obj_id = regs[regno].ref_obj_id;
u32 id = regs[regno].id;
int i, j;
if (ref_obj_id && ref_obj_id == id && is_null)
/* regs[regno] is in the " == NULL" branch.
* No one could have freed the reference state before
* doing the NULL check.
*/
WARN_ON_ONCE(release_reference_state(state, id));
for (i = 0; i < MAX_BPF_REG; i++)
mark_ptr_or_null_reg(state, &regs[i], id, is_null);
for (j = 0; j <= vstate->curframe; j++) {
state = vstate->frame[j];
bpf_for_each_spilled_reg(i, state, reg) {
if (!reg)
continue;
mark_ptr_or_null_reg(state, reg, id, is_null);
}
}
}
static bool try_match_pkt_pointers(const struct bpf_insn *insn,
struct bpf_reg_state *dst_reg,
struct bpf_reg_state *src_reg,
struct bpf_verifier_state *this_branch,
struct bpf_verifier_state *other_branch)
{
if (BPF_SRC(insn->code) != BPF_X)
return false;
/* Pointers are always 64-bit. */
if (BPF_CLASS(insn->code) == BPF_JMP32)
return false;
switch (BPF_OP(insn->code)) {
case BPF_JGT:
if ((dst_reg->type == PTR_TO_PACKET &&
src_reg->type == PTR_TO_PACKET_END) ||
(dst_reg->type == PTR_TO_PACKET_META &&
reg_is_init_pkt_pointer(src_reg, PTR_TO_PACKET))) {
/* pkt_data' > pkt_end, pkt_meta' > pkt_data */
find_good_pkt_pointers(this_branch, dst_reg,
dst_reg->type, false);
} else if ((dst_reg->type == PTR_TO_PACKET_END &&
src_reg->type == PTR_TO_PACKET) ||
(reg_is_init_pkt_pointer(dst_reg, PTR_TO_PACKET) &&
src_reg->type == PTR_TO_PACKET_META)) {
/* pkt_end > pkt_data', pkt_data > pkt_meta' */
find_good_pkt_pointers(other_branch, src_reg,
src_reg->type, true);
} else {
return false;
}
break;
case BPF_JLT:
if ((dst_reg->type == PTR_TO_PACKET &&
src_reg->type == PTR_TO_PACKET_END) ||
(dst_reg->type == PTR_TO_PACKET_META &&
reg_is_init_pkt_pointer(src_reg, PTR_TO_PACKET))) {
/* pkt_data' < pkt_end, pkt_meta' < pkt_data */
find_good_pkt_pointers(other_branch, dst_reg,
dst_reg->type, true);
} else if ((dst_reg->type == PTR_TO_PACKET_END &&
src_reg->type == PTR_TO_PACKET) ||
(reg_is_init_pkt_pointer(dst_reg, PTR_TO_PACKET) &&
src_reg->type == PTR_TO_PACKET_META)) {
/* pkt_end < pkt_data', pkt_data > pkt_meta' */
find_good_pkt_pointers(this_branch, src_reg,
src_reg->type, false);
} else {
return false;
}
break;
case BPF_JGE:
if ((dst_reg->type == PTR_TO_PACKET &&
src_reg->type == PTR_TO_PACKET_END) ||
(dst_reg->type == PTR_TO_PACKET_META &&
reg_is_init_pkt_pointer(src_reg, PTR_TO_PACKET))) {
/* pkt_data' >= pkt_end, pkt_meta' >= pkt_data */
find_good_pkt_pointers(this_branch, dst_reg,
dst_reg->type, true);
} else if ((dst_reg->type == PTR_TO_PACKET_END &&
src_reg->type == PTR_TO_PACKET) ||
(reg_is_init_pkt_pointer(dst_reg, PTR_TO_PACKET) &&
src_reg->type == PTR_TO_PACKET_META)) {
/* pkt_end >= pkt_data', pkt_data >= pkt_meta' */
find_good_pkt_pointers(other_branch, src_reg,
src_reg->type, false);
} else {
return false;
}
break;
case BPF_JLE:
if ((dst_reg->type == PTR_TO_PACKET &&
src_reg->type == PTR_TO_PACKET_END) ||
(dst_reg->type == PTR_TO_PACKET_META &&
reg_is_init_pkt_pointer(src_reg, PTR_TO_PACKET))) {
/* pkt_data' <= pkt_end, pkt_meta' <= pkt_data */
find_good_pkt_pointers(other_branch, dst_reg,
dst_reg->type, false);
} else if ((dst_reg->type == PTR_TO_PACKET_END &&
src_reg->type == PTR_TO_PACKET) ||
(reg_is_init_pkt_pointer(dst_reg, PTR_TO_PACKET) &&
src_reg->type == PTR_TO_PACKET_META)) {
/* pkt_end <= pkt_data', pkt_data <= pkt_meta' */
find_good_pkt_pointers(this_branch, src_reg,
src_reg->type, true);
} else {
return false;
}
break;
default:
return false;
}
return true;
}
static int check_cond_jmp_op(struct bpf_verifier_env *env,
struct bpf_insn *insn, int *insn_idx)
{
struct bpf_verifier_state *this_branch = env->cur_state;
struct bpf_verifier_state *other_branch;
struct bpf_reg_state *regs = this_branch->frame[this_branch->curframe]->regs;
struct bpf_reg_state *dst_reg, *other_branch_regs;
u8 opcode = BPF_OP(insn->code);
bool is_jmp32;
int err;
/* Only conditional jumps are expected to reach here. */
if (opcode == BPF_JA || opcode > BPF_JSLE) {
verbose(env, "invalid BPF_JMP/JMP32 opcode %x\n", opcode);
return -EINVAL;
}
if (BPF_SRC(insn->code) == BPF_X) {
if (insn->imm != 0) {
verbose(env, "BPF_JMP/JMP32 uses reserved fields\n");
return -EINVAL;
}
/* check src1 operand */
err = check_reg_arg(env, insn->src_reg, SRC_OP);
if (err)
return err;
if (is_pointer_value(env, insn->src_reg)) {
verbose(env, "R%d pointer comparison prohibited\n",
insn->src_reg);
return -EACCES;
}
} else {
if (insn->src_reg != BPF_REG_0) {
verbose(env, "BPF_JMP/JMP32 uses reserved fields\n");
return -EINVAL;
}
}
/* check src2 operand */
err = check_reg_arg(env, insn->dst_reg, SRC_OP);
if (err)
return err;
dst_reg = &regs[insn->dst_reg];
is_jmp32 = BPF_CLASS(insn->code) == BPF_JMP32;
if (BPF_SRC(insn->code) == BPF_K) {
int pred = is_branch_taken(dst_reg, insn->imm, opcode,
is_jmp32);
if (pred == 1) {
/* only follow the goto, ignore fall-through */
*insn_idx += insn->off;
return 0;
} else if (pred == 0) {
/* only follow fall-through branch, since
* that's where the program will go
*/
return 0;
}
}
other_branch = push_stack(env, *insn_idx + insn->off + 1, *insn_idx,
false);
if (!other_branch)
return -EFAULT;
other_branch_regs = other_branch->frame[other_branch->curframe]->regs;
/* detect if we are comparing against a constant value so we can adjust
* our min/max values for our dst register.
* this is only legit if both are scalars (or pointers to the same
* object, I suppose, but we don't support that right now), because
* otherwise the different base pointers mean the offsets aren't
* comparable.
*/
if (BPF_SRC(insn->code) == BPF_X) {
struct bpf_reg_state *src_reg = &regs[insn->src_reg];
struct bpf_reg_state lo_reg0 = *dst_reg;
struct bpf_reg_state lo_reg1 = *src_reg;
struct bpf_reg_state *src_lo, *dst_lo;
dst_lo = &lo_reg0;
src_lo = &lo_reg1;
coerce_reg_to_size(dst_lo, 4);
coerce_reg_to_size(src_lo, 4);
if (dst_reg->type == SCALAR_VALUE &&
src_reg->type == SCALAR_VALUE) {
if (tnum_is_const(src_reg->var_off) ||
(is_jmp32 && tnum_is_const(src_lo->var_off)))
reg_set_min_max(&other_branch_regs[insn->dst_reg],
dst_reg,
is_jmp32
? src_lo->var_off.value
: src_reg->var_off.value,
opcode, is_jmp32);
else if (tnum_is_const(dst_reg->var_off) ||
(is_jmp32 && tnum_is_const(dst_lo->var_off)))
reg_set_min_max_inv(&other_branch_regs[insn->src_reg],
src_reg,
is_jmp32
? dst_lo->var_off.value
: dst_reg->var_off.value,
opcode, is_jmp32);
else if (!is_jmp32 &&
(opcode == BPF_JEQ || opcode == BPF_JNE))
/* Comparing for equality, we can combine knowledge */
reg_combine_min_max(&other_branch_regs[insn->src_reg],
&other_branch_regs[insn->dst_reg],
src_reg, dst_reg, opcode);
}
} else if (dst_reg->type == SCALAR_VALUE) {
reg_set_min_max(&other_branch_regs[insn->dst_reg],
dst_reg, insn->imm, opcode, is_jmp32);
}
/* detect if R == 0 where R is returned from bpf_map_lookup_elem().
* NOTE: these optimizations below are related with pointer comparison
* which will never be JMP32.
*/
if (!is_jmp32 && BPF_SRC(insn->code) == BPF_K &&
insn->imm == 0 && (opcode == BPF_JEQ || opcode == BPF_JNE) &&
reg_type_may_be_null(dst_reg->type)) {
/* Mark all identical registers in each branch as either
* safe or unknown depending R == 0 or R != 0 conditional.
*/
mark_ptr_or_null_regs(this_branch, insn->dst_reg,
opcode == BPF_JNE);
mark_ptr_or_null_regs(other_branch, insn->dst_reg,
opcode == BPF_JEQ);
} else if (!try_match_pkt_pointers(insn, dst_reg, &regs[insn->src_reg],
this_branch, other_branch) &&
is_pointer_value(env, insn->dst_reg)) {
verbose(env, "R%d pointer comparison prohibited\n",
insn->dst_reg);
return -EACCES;
}
if (env->log.level)
print_verifier_state(env, this_branch->frame[this_branch->curframe]);
return 0;
}
/* return the map pointer stored inside BPF_LD_IMM64 instruction */
static struct bpf_map *ld_imm64_to_map_ptr(struct bpf_insn *insn)
{
u64 imm64 = ((u64) (u32) insn[0].imm) | ((u64) (u32) insn[1].imm) << 32;
return (struct bpf_map *) (unsigned long) imm64;
}
/* verify BPF_LD_IMM64 instruction */
static int check_ld_imm(struct bpf_verifier_env *env, struct bpf_insn *insn)
{
struct bpf_reg_state *regs = cur_regs(env);
int err;
if (BPF_SIZE(insn->code) != BPF_DW) {
verbose(env, "invalid BPF_LD_IMM insn\n");
return -EINVAL;
}
if (insn->off != 0) {
verbose(env, "BPF_LD_IMM64 uses reserved fields\n");
return -EINVAL;
}
err = check_reg_arg(env, insn->dst_reg, DST_OP);
if (err)
return err;
if (insn->src_reg == 0) {
u64 imm = ((u64)(insn + 1)->imm << 32) | (u32)insn->imm;
regs[insn->dst_reg].type = SCALAR_VALUE;
__mark_reg_known(&regs[insn->dst_reg], imm);
return 0;
}
/* replace_map_fd_with_map_ptr() should have caught bad ld_imm64 */
BUG_ON(insn->src_reg != BPF_PSEUDO_MAP_FD);
regs[insn->dst_reg].type = CONST_PTR_TO_MAP;
regs[insn->dst_reg].map_ptr = ld_imm64_to_map_ptr(insn);
return 0;
}
static bool may_access_skb(enum bpf_prog_type type)
{
switch (type) {
case BPF_PROG_TYPE_SOCKET_FILTER:
case BPF_PROG_TYPE_SCHED_CLS:
case BPF_PROG_TYPE_SCHED_ACT:
return true;
default:
return false;
}
}
/* verify safety of LD_ABS|LD_IND instructions:
* - they can only appear in the programs where ctx == skb
* - since they are wrappers of function calls, they scratch R1-R5 registers,
* preserve R6-R9, and store return value into R0
*
* Implicit input:
* ctx == skb == R6 == CTX
*
* Explicit input:
* SRC == any register
* IMM == 32-bit immediate
*
* Output:
* R0 - 8/16/32-bit skb data converted to cpu endianness
*/
static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn)
{
struct bpf_reg_state *regs = cur_regs(env);
u8 mode = BPF_MODE(insn->code);
int i, err;
if (!may_access_skb(env->prog->type)) {
verbose(env, "BPF_LD_[ABS|IND] instructions not allowed for this program type\n");
return -EINVAL;
}
if (!env->ops->gen_ld_abs) {
verbose(env, "bpf verifier is misconfigured\n");
return -EINVAL;
}
if (env->subprog_cnt > 1) {
/* when program has LD_ABS insn JITs and interpreter assume
* that r1 == ctx == skb which is not the case for callees
* that can have arbitrary arguments. It's problematic
* for main prog as well since JITs would need to analyze
* all functions in order to make proper register save/restore
* decisions in the main prog. Hence disallow LD_ABS with calls
*/
verbose(env, "BPF_LD_[ABS|IND] instructions cannot be mixed with bpf-to-bpf calls\n");
return -EINVAL;
}
if (insn->dst_reg != BPF_REG_0 || insn->off != 0 ||
BPF_SIZE(insn->code) == BPF_DW ||
(mode == BPF_ABS && insn->src_reg != BPF_REG_0)) {
verbose(env, "BPF_LD_[ABS|IND] uses reserved fields\n");
return -EINVAL;
}
/* check whether implicit source operand (register R6) is readable */
err = check_reg_arg(env, BPF_REG_6, SRC_OP);
if (err)
return err;
/* Disallow usage of BPF_LD_[ABS|IND] with reference tracking, as
* gen_ld_abs() may terminate the program at runtime, leading to
* reference leak.
*/
err = check_reference_leak(env);
if (err) {
verbose(env, "BPF_LD_[ABS|IND] cannot be mixed with socket references\n");
return err;
}
if (env->cur_state->active_spin_lock) {
verbose(env, "BPF_LD_[ABS|IND] cannot be used inside bpf_spin_lock-ed region\n");
return -EINVAL;
}
if (regs[BPF_REG_6].type != PTR_TO_CTX) {
verbose(env,
"at the time of BPF_LD_ABS|IND R6 != pointer to skb\n");
return -EINVAL;
}
if (mode == BPF_IND) {
/* check explicit source operand */
err = check_reg_arg(env, insn->src_reg, SRC_OP);
if (err)
return err;
}
/* reset caller saved regs to unreadable */
for (i = 0; i < CALLER_SAVED_REGS; i++) {
mark_reg_not_init(env, regs, caller_saved[i]);
check_reg_arg(env, caller_saved[i], DST_OP_NO_MARK);
}
/* mark destination R0 register as readable, since it contains
* the value fetched from the packet.
* Already marked as written above.
*/
mark_reg_unknown(env, regs, BPF_REG_0);
return 0;
}
static int check_return_code(struct bpf_verifier_env *env)
{
struct bpf_reg_state *reg;
struct tnum range = tnum_range(0, 1);
switch (env->prog->type) {
case BPF_PROG_TYPE_CGROUP_SKB:
case BPF_PROG_TYPE_CGROUP_SOCK:
case BPF_PROG_TYPE_CGROUP_SOCK_ADDR:
case BPF_PROG_TYPE_SOCK_OPS:
case BPF_PROG_TYPE_CGROUP_DEVICE:
break;
default:
return 0;
}
reg = cur_regs(env) + BPF_REG_0;
if (reg->type != SCALAR_VALUE) {
verbose(env, "At program exit the register R0 is not a known value (%s)\n",
reg_type_str[reg->type]);
return -EINVAL;
}
if (!tnum_in(range, reg->var_off)) {
verbose(env, "At program exit the register R0 ");
if (!tnum_is_unknown(reg->var_off)) {
char tn_buf[48];
tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
verbose(env, "has value %s", tn_buf);
} else {
verbose(env, "has unknown scalar value");
}
verbose(env, " should have been 0 or 1\n");
return -EINVAL;
}
return 0;
}
/* non-recursive DFS pseudo code
* 1 procedure DFS-iterative(G,v):
* 2 label v as discovered
* 3 let S be a stack
* 4 S.push(v)
* 5 while S is not empty
* 6 t <- S.pop()
* 7 if t is what we're looking for:
* 8 return t
* 9 for all edges e in G.adjacentEdges(t) do
* 10 if edge e is already labelled
* 11 continue with the next edge
* 12 w <- G.adjacentVertex(t,e)
* 13 if vertex w is not discovered and not explored
* 14 label e as tree-edge
* 15 label w as discovered
* 16 S.push(w)
* 17 continue at 5
* 18 else if vertex w is discovered
* 19 label e as back-edge
* 20 else
* 21 // vertex w is explored
* 22 label e as forward- or cross-edge
* 23 label t as explored
* 24 S.pop()
*
* convention:
* 0x10 - discovered
* 0x11 - discovered and fall-through edge labelled
* 0x12 - discovered and fall-through and branch edges labelled
* 0x20 - explored
*/
enum {
DISCOVERED = 0x10,
EXPLORED = 0x20,
FALLTHROUGH = 1,
BRANCH = 2,
};
#define STATE_LIST_MARK ((struct bpf_verifier_state_list *) -1L)
static int *insn_stack; /* stack of insns to process */
static int cur_stack; /* current stack index */
static int *insn_state;
/* t, w, e - match pseudo-code above:
* t - index of current instruction
* w - next instruction
* e - edge
*/
static int push_insn(int t, int w, int e, struct bpf_verifier_env *env)
{
if (e == FALLTHROUGH && insn_state[t] >= (DISCOVERED | FALLTHROUGH))
return 0;
if (e == BRANCH && insn_state[t] >= (DISCOVERED | BRANCH))
return 0;
if (w < 0 || w >= env->prog->len) {
verbose_linfo(env, t, "%d: ", t);
verbose(env, "jump out of range from insn %d to %d\n", t, w);
return -EINVAL;
}
if (e == BRANCH)
/* mark branch target for state pruning */
env->explored_states[w] = STATE_LIST_MARK;
if (insn_state[w] == 0) {
/* tree-edge */
insn_state[t] = DISCOVERED | e;
insn_state[w] = DISCOVERED;
if (cur_stack >= env->prog->len)
return -E2BIG;
insn_stack[cur_stack++] = w;
return 1;
} else if ((insn_state[w] & 0xF0) == DISCOVERED) {
verbose_linfo(env, t, "%d: ", t);
verbose_linfo(env, w, "%d: ", w);
verbose(env, "back-edge from insn %d to %d\n", t, w);
return -EINVAL;
} else if (insn_state[w] == EXPLORED) {
/* forward- or cross-edge */
insn_state[t] = DISCOVERED | e;
} else {
verbose(env, "insn state internal bug\n");
return -EFAULT;
}
return 0;
}
/* non-recursive depth-first-search to detect loops in BPF program
* loop == back-edge in directed graph
*/
static int check_cfg(struct bpf_verifier_env *env)
{
struct bpf_insn *insns = env->prog->insnsi;
int insn_cnt = env->prog->len;
int ret = 0;
int i, t;
insn_state = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
if (!insn_state)
return -ENOMEM;
insn_stack = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
if (!insn_stack) {
kfree(insn_state);
return -ENOMEM;
}
insn_state[0] = DISCOVERED; /* mark 1st insn as discovered */
insn_stack[0] = 0; /* 0 is the first instruction */
cur_stack = 1;
peek_stack:
if (cur_stack == 0)
goto check_state;
t = insn_stack[cur_stack - 1];
if (BPF_CLASS(insns[t].code) == BPF_JMP ||
BPF_CLASS(insns[t].code) == BPF_JMP32) {
u8 opcode = BPF_OP(insns[t].code);
if (opcode == BPF_EXIT) {
goto mark_explored;
} else if (opcode == BPF_CALL) {
ret = push_insn(t, t + 1, FALLTHROUGH, env);
if (ret == 1)
goto peek_stack;
else if (ret < 0)
goto err_free;
if (t + 1 < insn_cnt)
env->explored_states[t + 1] = STATE_LIST_MARK;
if (insns[t].src_reg == BPF_PSEUDO_CALL) {
env->explored_states[t] = STATE_LIST_MARK;
ret = push_insn(t, t + insns[t].imm + 1, BRANCH, env);
if (ret == 1)
goto peek_stack;
else if (ret < 0)
goto err_free;
}
} else if (opcode == BPF_JA) {
if (BPF_SRC(insns[t].code) != BPF_K) {
ret = -EINVAL;
goto err_free;
}
/* unconditional jump with single edge */
ret = push_insn(t, t + insns[t].off + 1,
FALLTHROUGH, env);
if (ret == 1)
goto peek_stack;
else if (ret < 0)
goto err_free;
/* tell verifier to check for equivalent states
* after every call and jump
*/
if (t + 1 < insn_cnt)
env->explored_states[t + 1] = STATE_LIST_MARK;
} else {
/* conditional jump with two edges */
env->explored_states[t] = STATE_LIST_MARK;
ret = push_insn(t, t + 1, FALLTHROUGH, env);
if (ret == 1)
goto peek_stack;
else if (ret < 0)
goto err_free;
ret = push_insn(t, t + insns[t].off + 1, BRANCH, env);
if (ret == 1)
goto peek_stack;
else if (ret < 0)
goto err_free;
}
} else {
/* all other non-branch instructions with single
* fall-through edge
*/
ret = push_insn(t, t + 1, FALLTHROUGH, env);
if (ret == 1)
goto peek_stack;
else if (ret < 0)
goto err_free;
}
mark_explored:
insn_state[t] = EXPLORED;
if (cur_stack-- <= 0) {
verbose(env, "pop stack internal bug\n");
ret = -EFAULT;
goto err_free;
}
goto peek_stack;
check_state:
for (i = 0; i < insn_cnt; i++) {
if (insn_state[i] != EXPLORED) {
verbose(env, "unreachable insn %d\n", i);
ret = -EINVAL;
goto err_free;
}
}
ret = 0; /* cfg looks good */
err_free:
kfree(insn_state);
kfree(insn_stack);
return ret;
}
/* The minimum supported BTF func info size */
#define MIN_BPF_FUNCINFO_SIZE 8
#define MAX_FUNCINFO_REC_SIZE 252
static int check_btf_func(struct bpf_verifier_env *env,
const union bpf_attr *attr,
union bpf_attr __user *uattr)
{
u32 i, nfuncs, urec_size, min_size;
u32 krec_size = sizeof(struct bpf_func_info);
struct bpf_func_info *krecord;
const struct btf_type *type;
struct bpf_prog *prog;
const struct btf *btf;
void __user *urecord;
u32 prev_offset = 0;
int ret = 0;
nfuncs = attr->func_info_cnt;
if (!nfuncs)
return 0;
if (nfuncs != env->subprog_cnt) {
verbose(env, "number of funcs in func_info doesn't match number of subprogs\n");
return -EINVAL;
}
urec_size = attr->func_info_rec_size;
if (urec_size < MIN_BPF_FUNCINFO_SIZE ||
urec_size > MAX_FUNCINFO_REC_SIZE ||
urec_size % sizeof(u32)) {
verbose(env, "invalid func info rec size %u\n", urec_size);
return -EINVAL;
}
prog = env->prog;
btf = prog->aux->btf;
urecord = u64_to_user_ptr(attr->func_info);
min_size = min_t(u32, krec_size, urec_size);
krecord = kvcalloc(nfuncs, krec_size, GFP_KERNEL | __GFP_NOWARN);
if (!krecord)
return -ENOMEM;
for (i = 0; i < nfuncs; i++) {
ret = bpf_check_uarg_tail_zero(urecord, krec_size, urec_size);
if (ret) {
if (ret == -E2BIG) {
verbose(env, "nonzero tailing record in func info");
/* set the size kernel expects so loader can zero
* out the rest of the record.
*/
if (put_user(min_size, &uattr->func_info_rec_size))
ret = -EFAULT;
}
goto err_free;
}
if (copy_from_user(&krecord[i], urecord, min_size)) {
ret = -EFAULT;
goto err_free;
}
/* check insn_off */
if (i == 0) {
if (krecord[i].insn_off) {
verbose(env,
"nonzero insn_off %u for the first func info record",
krecord[i].insn_off);
ret = -EINVAL;
goto err_free;
}
} else if (krecord[i].insn_off <= prev_offset) {
verbose(env,
"same or smaller insn offset (%u) than previous func info record (%u)",
krecord[i].insn_off, prev_offset);
ret = -EINVAL;
goto err_free;
}
if (env->subprog_info[i].start != krecord[i].insn_off) {
verbose(env, "func_info BTF section doesn't match subprog layout in BPF program\n");
ret = -EINVAL;
goto err_free;
}
/* check type_id */
type = btf_type_by_id(btf, krecord[i].type_id);
if (!type || BTF_INFO_KIND(type->info) != BTF_KIND_FUNC) {
verbose(env, "invalid type id %d in func info",
krecord[i].type_id);
ret = -EINVAL;
goto err_free;
}
prev_offset = krecord[i].insn_off;
urecord += urec_size;
}
prog->aux->func_info = krecord;
prog->aux->func_info_cnt = nfuncs;
return 0;
err_free:
kvfree(krecord);
return ret;
}
static void adjust_btf_func(struct bpf_verifier_env *env)
{
int i;
if (!env->prog->aux->func_info)
return;
for (i = 0; i < env->subprog_cnt; i++)
env->prog->aux->func_info[i].insn_off = env->subprog_info[i].start;
}
#define MIN_BPF_LINEINFO_SIZE (offsetof(struct bpf_line_info, line_col) + \
sizeof(((struct bpf_line_info *)(0))->line_col))
#define MAX_LINEINFO_REC_SIZE MAX_FUNCINFO_REC_SIZE
static int check_btf_line(struct bpf_verifier_env *env,
const union bpf_attr *attr,
union bpf_attr __user *uattr)
{
u32 i, s, nr_linfo, ncopy, expected_size, rec_size, prev_offset = 0;
struct bpf_subprog_info *sub;
struct bpf_line_info *linfo;
struct bpf_prog *prog;
const struct btf *btf;
void __user *ulinfo;
int err;
nr_linfo = attr->line_info_cnt;
if (!nr_linfo)
return 0;
rec_size = attr->line_info_rec_size;
if (rec_size < MIN_BPF_LINEINFO_SIZE ||
rec_size > MAX_LINEINFO_REC_SIZE ||
rec_size & (sizeof(u32) - 1))
return -EINVAL;
/* Need to zero it in case the userspace may
* pass in a smaller bpf_line_info object.
*/
linfo = kvcalloc(nr_linfo, sizeof(struct bpf_line_info),
GFP_KERNEL | __GFP_NOWARN);
if (!linfo)
return -ENOMEM;
prog = env->prog;
btf = prog->aux->btf;
s = 0;
sub = env->subprog_info;
ulinfo = u64_to_user_ptr(attr->line_info);
expected_size = sizeof(struct bpf_line_info);
ncopy = min_t(u32, expected_size, rec_size);
for (i = 0; i < nr_linfo; i++) {
err = bpf_check_uarg_tail_zero(ulinfo, expected_size, rec_size);
if (err) {
if (err == -E2BIG) {
verbose(env, "nonzero tailing record in line_info");
if (put_user(expected_size,
&uattr->line_info_rec_size))
err = -EFAULT;
}
goto err_free;
}
if (copy_from_user(&linfo[i], ulinfo, ncopy)) {
err = -EFAULT;
goto err_free;
}
/*
* Check insn_off to ensure
* 1) strictly increasing AND
* 2) bounded by prog->len
*
* The linfo[0].insn_off == 0 check logically falls into
* the later "missing bpf_line_info for func..." case
* because the first linfo[0].insn_off must be the
* first sub also and the first sub must have
* subprog_info[0].start == 0.
*/
if ((i && linfo[i].insn_off <= prev_offset) ||
linfo[i].insn_off >= prog->len) {
verbose(env, "Invalid line_info[%u].insn_off:%u (prev_offset:%u prog->len:%u)\n",
i, linfo[i].insn_off, prev_offset,
prog->len);
err = -EINVAL;
goto err_free;
}
if (!prog->insnsi[linfo[i].insn_off].code) {
verbose(env,
"Invalid insn code at line_info[%u].insn_off\n",
i);
err = -EINVAL;
goto err_free;
}
if (!btf_name_by_offset(btf, linfo[i].line_off) ||
!btf_name_by_offset(btf, linfo[i].file_name_off)) {
verbose(env, "Invalid line_info[%u].line_off or .file_name_off\n", i);
err = -EINVAL;
goto err_free;
}
if (s != env->subprog_cnt) {
if (linfo[i].insn_off == sub[s].start) {
sub[s].linfo_idx = i;
s++;
} else if (sub[s].start < linfo[i].insn_off) {
verbose(env, "missing bpf_line_info for func#%u\n", s);
err = -EINVAL;
goto err_free;
}
}
prev_offset = linfo[i].insn_off;
ulinfo += rec_size;
}
if (s != env->subprog_cnt) {
verbose(env, "missing bpf_line_info for %u funcs starting from func#%u\n",
env->subprog_cnt - s, s);
err = -EINVAL;
goto err_free;
}
prog->aux->linfo = linfo;
prog->aux->nr_linfo = nr_linfo;
return 0;
err_free:
kvfree(linfo);
return err;
}
static int check_btf_info(struct bpf_verifier_env *env,
const union bpf_attr *attr,
union bpf_attr __user *uattr)
{
struct btf *btf;
int err;
if (!attr->func_info_cnt && !attr->line_info_cnt)
return 0;
btf = btf_get_by_fd(attr->prog_btf_fd);
if (IS_ERR(btf))
return PTR_ERR(btf);
env->prog->aux->btf = btf;
err = check_btf_func(env, attr, uattr);
if (err)
return err;
err = check_btf_line(env, attr, uattr);
if (err)
return err;
return 0;
}
/* check %cur's range satisfies %old's */
static bool range_within(struct bpf_reg_state *old,
struct bpf_reg_state *cur)
{
return old->umin_value <= cur->umin_value &&
old->umax_value >= cur->umax_value &&
old->smin_value <= cur->smin_value &&
old->smax_value >= cur->smax_value;
}
/* Maximum number of register states that can exist at once */
#define ID_MAP_SIZE (MAX_BPF_REG + MAX_BPF_STACK / BPF_REG_SIZE)
struct idpair {
u32 old;
u32 cur;
};
/* If in the old state two registers had the same id, then they need to have
* the same id in the new state as well. But that id could be different from
* the old state, so we need to track the mapping from old to new ids.
* Once we have seen that, say, a reg with old id 5 had new id 9, any subsequent
* regs with old id 5 must also have new id 9 for the new state to be safe. But
* regs with a different old id could still have new id 9, we don't care about
* that.
* So we look through our idmap to see if this old id has been seen before. If
* so, we require the new id to match; otherwise, we add the id pair to the map.
*/
static bool check_ids(u32 old_id, u32 cur_id, struct idpair *idmap)
{
unsigned int i;
for (i = 0; i < ID_MAP_SIZE; i++) {
if (!idmap[i].old) {
/* Reached an empty slot; haven't seen this id before */
idmap[i].old = old_id;
idmap[i].cur = cur_id;
return true;
}
if (idmap[i].old == old_id)
return idmap[i].cur == cur_id;
}
/* We ran out of idmap slots, which should be impossible */
WARN_ON_ONCE(1);
return false;
}
static void clean_func_state(struct bpf_verifier_env *env,
struct bpf_func_state *st)
{
enum bpf_reg_liveness live;
int i, j;
for (i = 0; i < BPF_REG_FP; i++) {
live = st->regs[i].live;
/* liveness must not touch this register anymore */
st->regs[i].live |= REG_LIVE_DONE;
if (!(live & REG_LIVE_READ))
/* since the register is unused, clear its state
* to make further comparison simpler
*/
__mark_reg_not_init(&st->regs[i]);
}
for (i = 0; i < st->allocated_stack / BPF_REG_SIZE; i++) {
live = st->stack[i].spilled_ptr.live;
/* liveness must not touch this stack slot anymore */
st->stack[i].spilled_ptr.live |= REG_LIVE_DONE;
if (!(live & REG_LIVE_READ)) {
__mark_reg_not_init(&st->stack[i].spilled_ptr);
for (j = 0; j < BPF_REG_SIZE; j++)
st->stack[i].slot_type[j] = STACK_INVALID;
}
}
}
static void clean_verifier_state(struct bpf_verifier_env *env,
struct bpf_verifier_state *st)
{
int i;
if (st->frame[0]->regs[0].live & REG_LIVE_DONE)
/* all regs in this state in all frames were already marked */
return;
for (i = 0; i <= st->curframe; i++)
clean_func_state(env, st->frame[i]);
}
/* the parentage chains form a tree.
* the verifier states are added to state lists at given insn and
* pushed into state stack for future exploration.
* when the verifier reaches bpf_exit insn some of the verifer states
* stored in the state lists have their final liveness state already,
* but a lot of states will get revised from liveness point of view when
* the verifier explores other branches.
* Example:
* 1: r0 = 1
* 2: if r1 == 100 goto pc+1
* 3: r0 = 2
* 4: exit
* when the verifier reaches exit insn the register r0 in the state list of
* insn 2 will be seen as !REG_LIVE_READ. Then the verifier pops the other_branch
* of insn 2 and goes exploring further. At the insn 4 it will walk the
* parentage chain from insn 4 into insn 2 and will mark r0 as REG_LIVE_READ.
*
* Since the verifier pushes the branch states as it sees them while exploring
* the program the condition of walking the branch instruction for the second
* time means that all states below this branch were already explored and
* their final liveness markes are already propagated.
* Hence when the verifier completes the search of state list in is_state_visited()
* we can call this clean_live_states() function to mark all liveness states
* as REG_LIVE_DONE to indicate that 'parent' pointers of 'struct bpf_reg_state'
* will not be used.
* This function also clears the registers and stack for states that !READ
* to simplify state merging.
*
* Important note here that walking the same branch instruction in the callee
* doesn't meant that the states are DONE. The verifier has to compare
* the callsites
*/
static void clean_live_states(struct bpf_verifier_env *env, int insn,
struct bpf_verifier_state *cur)
{
struct bpf_verifier_state_list *sl;
int i;
sl = env->explored_states[insn];
if (!sl)
return;
while (sl != STATE_LIST_MARK) {
if (sl->state.curframe != cur->curframe)
goto next;
for (i = 0; i <= cur->curframe; i++)
if (sl->state.frame[i]->callsite != cur->frame[i]->callsite)
goto next;
clean_verifier_state(env, &sl->state);
next:
sl = sl->next;
}
}
/* Returns true if (rold safe implies rcur safe) */
static bool regsafe(struct bpf_reg_state *rold, struct bpf_reg_state *rcur,
struct idpair *idmap)
{
bool equal;
if (!(rold->live & REG_LIVE_READ))
/* explored state didn't use this */
return true;
equal = memcmp(rold, rcur, offsetof(struct bpf_reg_state, parent)) == 0;
if (rold->type == PTR_TO_STACK)
/* two stack pointers are equal only if they're pointing to
* the same stack frame, since fp-8 in foo != fp-8 in bar
*/
return equal && rold->frameno == rcur->frameno;
if (equal)
return true;
if (rold->type == NOT_INIT)
/* explored state can't have used this */
return true;
if (rcur->type == NOT_INIT)
return false;
switch (rold->type) {
case SCALAR_VALUE:
if (rcur->type == SCALAR_VALUE) {
/* new val must satisfy old val knowledge */
return range_within(rold, rcur) &&
tnum_in(rold->var_off, rcur->var_off);
} else {
/* We're trying to use a pointer in place of a scalar.
* Even if the scalar was unbounded, this could lead to
* pointer leaks because scalars are allowed to leak
* while pointers are not. We could make this safe in
* special cases if root is calling us, but it's
* probably not worth the hassle.
*/
return false;
}
case PTR_TO_MAP_VALUE:
/* If the new min/max/var_off satisfy the old ones and
* everything else matches, we are OK.
* 'id' is not compared, since it's only used for maps with
* bpf_spin_lock inside map element and in such cases if
* the rest of the prog is valid for one map element then
* it's valid for all map elements regardless of the key
* used in bpf_map_lookup()
*/
return memcmp(rold, rcur, offsetof(struct bpf_reg_state, id)) == 0 &&
range_within(rold, rcur) &&
tnum_in(rold->var_off, rcur->var_off);
case PTR_TO_MAP_VALUE_OR_NULL:
/* a PTR_TO_MAP_VALUE could be safe to use as a
* PTR_TO_MAP_VALUE_OR_NULL into the same map.
* However, if the old PTR_TO_MAP_VALUE_OR_NULL then got NULL-
* checked, doing so could have affected others with the same
* id, and we can't check for that because we lost the id when
* we converted to a PTR_TO_MAP_VALUE.
*/
if (rcur->type != PTR_TO_MAP_VALUE_OR_NULL)
return false;
if (memcmp(rold, rcur, offsetof(struct bpf_reg_state, id)))
return false;
/* Check our ids match any regs they're supposed to */
return check_ids(rold->id, rcur->id, idmap);
case PTR_TO_PACKET_META:
case PTR_TO_PACKET:
if (rcur->type != rold->type)
return false;
/* We must have at least as much range as the old ptr
* did, so that any accesses which were safe before are
* still safe. This is true even if old range < old off,
* since someone could have accessed through (ptr - k), or
* even done ptr -= k in a register, to get a safe access.
*/
if (rold->range > rcur->range)
return false;
/* If the offsets don't match, we can't trust our alignment;
* nor can we be sure that we won't fall out of range.
*/
if (rold->off != rcur->off)
return false;
/* id relations must be preserved */
if (rold->id && !check_ids(rold->id, rcur->id, idmap))
return false;
/* new val must satisfy old val knowledge */
return range_within(rold, rcur) &&
tnum_in(rold->var_off, rcur->var_off);
case PTR_TO_CTX:
case CONST_PTR_TO_MAP:
case PTR_TO_PACKET_END:
case PTR_TO_FLOW_KEYS:
case PTR_TO_SOCKET:
case PTR_TO_SOCKET_OR_NULL:
case PTR_TO_SOCK_COMMON:
case PTR_TO_SOCK_COMMON_OR_NULL:
case PTR_TO_TCP_SOCK:
case PTR_TO_TCP_SOCK_OR_NULL:
/* Only valid matches are exact, which memcmp() above
* would have accepted
*/
default:
/* Don't know what's going on, just say it's not safe */
return false;
}
/* Shouldn't get here; if we do, say it's not safe */
WARN_ON_ONCE(1);
return false;
}
static bool stacksafe(struct bpf_func_state *old,
struct bpf_func_state *cur,
struct idpair *idmap)
{
int i, spi;
/* walk slots of the explored stack and ignore any additional
* slots in the current stack, since explored(safe) state
* didn't use them
*/
for (i = 0; i < old->allocated_stack; i++) {
spi = i / BPF_REG_SIZE;
if (!(old->stack[spi].spilled_ptr.live & REG_LIVE_READ)) {
i += BPF_REG_SIZE - 1;
/* explored state didn't use this */
continue;
}
if (old->stack[spi].slot_type[i % BPF_REG_SIZE] == STACK_INVALID)
continue;
/* explored stack has more populated slots than current stack
* and these slots were used
*/
if (i >= cur->allocated_stack)
return false;
/* if old state was safe with misc data in the stack
* it will be safe with zero-initialized stack.
* The opposite is not true
*/
if (old->stack[spi].slot_type[i % BPF_REG_SIZE] == STACK_MISC &&
cur->stack[spi].slot_type[i % BPF_REG_SIZE] == STACK_ZERO)
continue;
if (old->stack[spi].slot_type[i % BPF_REG_SIZE] !=
cur->stack[spi].slot_type[i % BPF_REG_SIZE])
/* Ex: old explored (safe) state has STACK_SPILL in
* this stack slot, but current has has STACK_MISC ->
* this verifier states are not equivalent,
* return false to continue verification of this path
*/
return false;
if (i % BPF_REG_SIZE)
continue;
if (old->stack[spi].slot_type[0] != STACK_SPILL)
continue;
if (!regsafe(&old->stack[spi].spilled_ptr,
&cur->stack[spi].spilled_ptr,
idmap))
/* when explored and current stack slot are both storing
* spilled registers, check that stored pointers types
* are the same as well.
* Ex: explored safe path could have stored
* (bpf_reg_state) {.type = PTR_TO_STACK, .off = -8}
* but current path has stored:
* (bpf_reg_state) {.type = PTR_TO_STACK, .off = -16}
* such verifier states are not equivalent.
* return false to continue verification of this path
*/
return false;
}
return true;
}
static bool refsafe(struct bpf_func_state *old, struct bpf_func_state *cur)
{
if (old->acquired_refs != cur->acquired_refs)
return false;
return !memcmp(old->refs, cur->refs,
sizeof(*old->refs) * old->acquired_refs);
}
/* compare two verifier states
*
* all states stored in state_list are known to be valid, since
* verifier reached 'bpf_exit' instruction through them
*
* this function is called when verifier exploring different branches of
* execution popped from the state stack. If it sees an old state that has
* more strict register state and more strict stack state then this execution
* branch doesn't need to be explored further, since verifier already
* concluded that more strict state leads to valid finish.
*
* Therefore two states are equivalent if register state is more conservative
* and explored stack state is more conservative than the current one.
* Example:
* explored current
* (slot1=INV slot2=MISC) == (slot1=MISC slot2=MISC)
* (slot1=MISC slot2=MISC) != (slot1=INV slot2=MISC)
*
* In other words if current stack state (one being explored) has more
* valid slots than old one that already passed validation, it means
* the verifier can stop exploring and conclude that current state is valid too
*
* Similarly with registers. If explored state has register type as invalid
* whereas register type in current state is meaningful, it means that
* the current state will reach 'bpf_exit' instruction safely
*/
static bool func_states_equal(struct bpf_func_state *old,
struct bpf_func_state *cur)
{
struct idpair *idmap;
bool ret = false;
int i;
idmap = kcalloc(ID_MAP_SIZE, sizeof(struct idpair), GFP_KERNEL);
/* If we failed to allocate the idmap, just say it's not safe */
if (!idmap)
return false;
for (i = 0; i < MAX_BPF_REG; i++) {
if (!regsafe(&old->regs[i], &cur->regs[i], idmap))
goto out_free;
}
if (!stacksafe(old, cur, idmap))
goto out_free;
if (!refsafe(old, cur))
goto out_free;
ret = true;
out_free:
kfree(idmap);
return ret;
}
static bool states_equal(struct bpf_verifier_env *env,
struct bpf_verifier_state *old,
struct bpf_verifier_state *cur)
{
int i;
if (old->curframe != cur->curframe)
return false;
/* Verification state from speculative execution simulation
* must never prune a non-speculative execution one.
*/
if (old->speculative && !cur->speculative)
return false;
if (old->active_spin_lock != cur->active_spin_lock)
return false;
/* for states to be equal callsites have to be the same
* and all frame states need to be equivalent
*/
for (i = 0; i <= old->curframe; i++) {
if (old->frame[i]->callsite != cur->frame[i]->callsite)
return false;
if (!func_states_equal(old->frame[i], cur->frame[i]))
return false;
}
return true;
}
/* A write screens off any subsequent reads; but write marks come from the
* straight-line code between a state and its parent. When we arrive at an
* equivalent state (jump target or such) we didn't arrive by the straight-line
* code, so read marks in the state must propagate to the parent regardless
* of the state's write marks. That's what 'parent == state->parent' comparison
* in mark_reg_read() is for.
*/
static int propagate_liveness(struct bpf_verifier_env *env,
const struct bpf_verifier_state *vstate,
struct bpf_verifier_state *vparent)
{
int i, frame, err = 0;
struct bpf_func_state *state, *parent;
if (vparent->curframe != vstate->curframe) {
WARN(1, "propagate_live: parent frame %d current frame %d\n",
vparent->curframe, vstate->curframe);
return -EFAULT;
}
/* Propagate read liveness of registers... */
BUILD_BUG_ON(BPF_REG_FP + 1 != MAX_BPF_REG);
for (frame = 0; frame <= vstate->curframe; frame++) {
/* We don't need to worry about FP liveness, it's read-only */
for (i = frame < vstate->curframe ? BPF_REG_6 : 0; i < BPF_REG_FP; i++) {
if (vparent->frame[frame]->regs[i].live & REG_LIVE_READ)
continue;
if (vstate->frame[frame]->regs[i].live & REG_LIVE_READ) {
err = mark_reg_read(env, &vstate->frame[frame]->regs[i],
&vparent->frame[frame]->regs[i]);
if (err)
return err;
}
}
}
/* ... and stack slots */
for (frame = 0; frame <= vstate->curframe; frame++) {
state = vstate->frame[frame];
parent = vparent->frame[frame];
for (i = 0; i < state->allocated_stack / BPF_REG_SIZE &&
i < parent->allocated_stack / BPF_REG_SIZE; i++) {
if (parent->stack[i].spilled_ptr.live & REG_LIVE_READ)
continue;
if (state->stack[i].spilled_ptr.live & REG_LIVE_READ)
mark_reg_read(env, &state->stack[i].spilled_ptr,
&parent->stack[i].spilled_ptr);
}
}
return err;
}
static int is_state_visited(struct bpf_verifier_env *env, int insn_idx)
{
struct bpf_verifier_state_list *new_sl;
struct bpf_verifier_state_list *sl;
struct bpf_verifier_state *cur = env->cur_state, *new;
int i, j, err, states_cnt = 0;
sl = env->explored_states[insn_idx];
if (!sl)
/* this 'insn_idx' instruction wasn't marked, so we will not
* be doing state search here
*/
return 0;
clean_live_states(env, insn_idx, cur);
while (sl != STATE_LIST_MARK) {
if (states_equal(env, &sl->state, cur)) {
/* reached equivalent register/stack state,
* prune the search.
* Registers read by the continuation are read by us.
* If we have any write marks in env->cur_state, they
* will prevent corresponding reads in the continuation
* from reaching our parent (an explored_state). Our
* own state will get the read marks recorded, but
* they'll be immediately forgotten as we're pruning
* this state and will pop a new one.
*/
err = propagate_liveness(env, &sl->state, cur);
if (err)
return err;
return 1;
}
sl = sl->next;
states_cnt++;
}
if (!env->allow_ptr_leaks && states_cnt > BPF_COMPLEXITY_LIMIT_STATES)
return 0;
/* there were no equivalent states, remember current one.
* technically the current state is not proven to be safe yet,
* but it will either reach outer most bpf_exit (which means it's safe)
* or it will be rejected. Since there are no loops, we won't be
* seeing this tuple (frame[0].callsite, frame[1].callsite, .. insn_idx)
* again on the way to bpf_exit
*/
new_sl = kzalloc(sizeof(struct bpf_verifier_state_list), GFP_KERNEL);
if (!new_sl)
return -ENOMEM;
/* add new state to the head of linked list */
new = &new_sl->state;
err = copy_verifier_state(new, cur);
if (err) {
free_verifier_state(new, false);
kfree(new_sl);
return err;
}
new_sl->next = env->explored_states[insn_idx];
env->explored_states[insn_idx] = new_sl;
/* connect new state to parentage chain. Current frame needs all
* registers connected. Only r6 - r9 of the callers are alive (pushed
* to the stack implicitly by JITs) so in callers' frames connect just
* r6 - r9 as an optimization. Callers will have r1 - r5 connected to
* the state of the call instruction (with WRITTEN set), and r0 comes
* from callee with its full parentage chain, anyway.
*/
for (j = 0; j <= cur->curframe; j++)
for (i = j < cur->curframe ? BPF_REG_6 : 0; i < BPF_REG_FP; i++)
cur->frame[j]->regs[i].parent = &new->frame[j]->regs[i];
/* clear write marks in current state: the writes we did are not writes
* our child did, so they don't screen off its reads from us.
* (There are no read marks in current state, because reads always mark
* their parent and current state never has children yet. Only
* explored_states can get read marks.)
*/
for (i = 0; i < BPF_REG_FP; i++)
cur->frame[cur->curframe]->regs[i].live = REG_LIVE_NONE;
/* all stack frames are accessible from callee, clear them all */
for (j = 0; j <= cur->curframe; j++) {
struct bpf_func_state *frame = cur->frame[j];
struct bpf_func_state *newframe = new->frame[j];
for (i = 0; i < frame->allocated_stack / BPF_REG_SIZE; i++) {
frame->stack[i].spilled_ptr.live = REG_LIVE_NONE;
frame->stack[i].spilled_ptr.parent =
&newframe->stack[i].spilled_ptr;
}
}
return 0;
}
/* Return true if it's OK to have the same insn return a different type. */
static bool reg_type_mismatch_ok(enum bpf_reg_type type)
{
switch (type) {
case PTR_TO_CTX:
case PTR_TO_SOCKET:
case PTR_TO_SOCKET_OR_NULL:
case PTR_TO_SOCK_COMMON:
case PTR_TO_SOCK_COMMON_OR_NULL:
case PTR_TO_TCP_SOCK:
case PTR_TO_TCP_SOCK_OR_NULL:
return false;
default:
return true;
}
}
/* If an instruction was previously used with particular pointer types, then we
* need to be careful to avoid cases such as the below, where it may be ok
* for one branch accessing the pointer, but not ok for the other branch:
*
* R1 = sock_ptr
* goto X;
* ...
* R1 = some_other_valid_ptr;
* goto X;
* ...
* R2 = *(u32 *)(R1 + 0);
*/
static bool reg_type_mismatch(enum bpf_reg_type src, enum bpf_reg_type prev)
{
return src != prev && (!reg_type_mismatch_ok(src) ||
!reg_type_mismatch_ok(prev));
}
static int do_check(struct bpf_verifier_env *env)
{
struct bpf_verifier_state *state;
struct bpf_insn *insns = env->prog->insnsi;
struct bpf_reg_state *regs;
int insn_cnt = env->prog->len, i;
int insn_processed = 0;
bool do_print_state = false;
env->prev_linfo = NULL;
state = kzalloc(sizeof(struct bpf_verifier_state), GFP_KERNEL);
if (!state)
return -ENOMEM;
state->curframe = 0;
state->speculative = false;
state->frame[0] = kzalloc(sizeof(struct bpf_func_state), GFP_KERNEL);
if (!state->frame[0]) {
kfree(state);
return -ENOMEM;
}
env->cur_state = state;
init_func_state(env, state->frame[0],
BPF_MAIN_FUNC /* callsite */,
0 /* frameno */,
0 /* subprogno, zero == main subprog */);
for (;;) {
struct bpf_insn *insn;
u8 class;
int err;
if (env->insn_idx >= insn_cnt) {
verbose(env, "invalid insn idx %d insn_cnt %d\n",
env->insn_idx, insn_cnt);
return -EFAULT;
}
insn = &insns[env->insn_idx];
class = BPF_CLASS(insn->code);
if (++insn_processed > BPF_COMPLEXITY_LIMIT_INSNS) {
verbose(env,
"BPF program is too large. Processed %d insn\n",
insn_processed);
return -E2BIG;
}
err = is_state_visited(env, env->insn_idx);
if (err < 0)
return err;
if (err == 1) {
/* found equivalent state, can prune the search */
if (env->log.level) {
if (do_print_state)
verbose(env, "\nfrom %d to %d%s: safe\n",
env->prev_insn_idx, env->insn_idx,
env->cur_state->speculative ?
" (speculative execution)" : "");
else
verbose(env, "%d: safe\n", env->insn_idx);
}
goto process_bpf_exit;
}
if (signal_pending(current))
return -EAGAIN;
if (need_resched())
cond_resched();
if (env->log.level > 1 || (env->log.level && do_print_state)) {
if (env->log.level > 1)
verbose(env, "%d:", env->insn_idx);
else
verbose(env, "\nfrom %d to %d%s:",
env->prev_insn_idx, env->insn_idx,
env->cur_state->speculative ?
" (speculative execution)" : "");
print_verifier_state(env, state->frame[state->curframe]);
do_print_state = false;
}
if (env->log.level) {
const struct bpf_insn_cbs cbs = {
.cb_print = verbose,
.private_data = env,
};
verbose_linfo(env, env->insn_idx, "; ");
verbose(env, "%d: ", env->insn_idx);
print_bpf_insn(&cbs, insn, env->allow_ptr_leaks);
}
if (bpf_prog_is_dev_bound(env->prog->aux)) {
err = bpf_prog_offload_verify_insn(env, env->insn_idx,
env->prev_insn_idx);
if (err)
return err;
}
regs = cur_regs(env);
env->insn_aux_data[env->insn_idx].seen = true;
if (class == BPF_ALU || class == BPF_ALU64) {
err = check_alu_op(env, insn);
if (err)
return err;
} else if (class == BPF_LDX) {
enum bpf_reg_type *prev_src_type, src_reg_type;
/* check for reserved fields is already done */
/* check src operand */
err = check_reg_arg(env, insn->src_reg, SRC_OP);
if (err)
return err;
err = check_reg_arg(env, insn->dst_reg, DST_OP_NO_MARK);
if (err)
return err;
src_reg_type = regs[insn->src_reg].type;
/* check that memory (src_reg + off) is readable,
* the state of dst_reg will be updated by this func
*/
err = check_mem_access(env, env->insn_idx, insn->src_reg,
insn->off, BPF_SIZE(insn->code),
BPF_READ, insn->dst_reg, false);
if (err)
return err;
prev_src_type = &env->insn_aux_data[env->insn_idx].ptr_type;
if (*prev_src_type == NOT_INIT) {
/* saw a valid insn
* dst_reg = *(u32 *)(src_reg + off)
* save type to validate intersecting paths
*/
*prev_src_type = src_reg_type;
} else if (reg_type_mismatch(src_reg_type, *prev_src_type)) {
/* ABuser program is trying to use the same insn
* dst_reg = *(u32*) (src_reg + off)
* with different pointer types:
* src_reg == ctx in one branch and
* src_reg == stack|map in some other branch.
* Reject it.
*/
verbose(env, "same insn cannot be used with different pointers\n");
return -EINVAL;
}
} else if (class == BPF_STX) {
enum bpf_reg_type *prev_dst_type, dst_reg_type;
if (BPF_MODE(insn->code) == BPF_XADD) {
err = check_xadd(env, env->insn_idx, insn);
if (err)
return err;
env->insn_idx++;
continue;
}
/* check src1 operand */
err = check_reg_arg(env, insn->src_reg, SRC_OP);
if (err)
return err;
/* check src2 operand */
err = check_reg_arg(env, insn->dst_reg, SRC_OP);
if (err)
return err;
dst_reg_type = regs[insn->dst_reg].type;
/* check that memory (dst_reg + off) is writeable */
err = check_mem_access(env, env->insn_idx, insn->dst_reg,
insn->off, BPF_SIZE(insn->code),
BPF_WRITE, insn->src_reg, false);
if (err)
return err;
prev_dst_type = &env->insn_aux_data[env->insn_idx].ptr_type;
if (*prev_dst_type == NOT_INIT) {
*prev_dst_type = dst_reg_type;
} else if (reg_type_mismatch(dst_reg_type, *prev_dst_type)) {
verbose(env, "same insn cannot be used with different pointers\n");
return -EINVAL;
}
} else if (class == BPF_ST) {
if (BPF_MODE(insn->code) != BPF_MEM ||
insn->src_reg != BPF_REG_0) {
verbose(env, "BPF_ST uses reserved fields\n");
return -EINVAL;
}
/* check src operand */
err = check_reg_arg(env, insn->dst_reg, SRC_OP);
if (err)
return err;
if (is_ctx_reg(env, insn->dst_reg)) {
verbose(env, "BPF_ST stores into R%d %s is not allowed\n",
insn->dst_reg,
reg_type_str[reg_state(env, insn->dst_reg)->type]);
return -EACCES;
}
/* check that memory (dst_reg + off) is writeable */
err = check_mem_access(env, env->insn_idx, insn->dst_reg,
insn->off, BPF_SIZE(insn->code),
BPF_WRITE, -1, false);
if (err)
return err;
} else if (class == BPF_JMP || class == BPF_JMP32) {
u8 opcode = BPF_OP(insn->code);
if (opcode == BPF_CALL) {
if (BPF_SRC(insn->code) != BPF_K ||
insn->off != 0 ||
(insn->src_reg != BPF_REG_0 &&
insn->src_reg != BPF_PSEUDO_CALL) ||
insn->dst_reg != BPF_REG_0 ||
class == BPF_JMP32) {
verbose(env, "BPF_CALL uses reserved fields\n");
return -EINVAL;
}
if (env->cur_state->active_spin_lock &&
(insn->src_reg == BPF_PSEUDO_CALL ||
insn->imm != BPF_FUNC_spin_unlock)) {
verbose(env, "function calls are not allowed while holding a lock\n");
return -EINVAL;
}
if (insn->src_reg == BPF_PSEUDO_CALL)
err = check_func_call(env, insn, &env->insn_idx);
else
err = check_helper_call(env, insn->imm, env->insn_idx);
if (err)
return err;
} else if (opcode == BPF_JA) {
if (BPF_SRC(insn->code) != BPF_K ||
insn->imm != 0 ||
insn->src_reg != BPF_REG_0 ||
insn->dst_reg != BPF_REG_0 ||
class == BPF_JMP32) {
verbose(env, "BPF_JA uses reserved fields\n");
return -EINVAL;
}
env->insn_idx += insn->off + 1;
continue;
} else if (opcode == BPF_EXIT) {
if (BPF_SRC(insn->code) != BPF_K ||
insn->imm != 0 ||
insn->src_reg != BPF_REG_0 ||
insn->dst_reg != BPF_REG_0 ||
class == BPF_JMP32) {
verbose(env, "BPF_EXIT uses reserved fields\n");
return -EINVAL;
}
if (env->cur_state->active_spin_lock) {
verbose(env, "bpf_spin_unlock is missing\n");
return -EINVAL;
}
if (state->curframe) {
/* exit from nested function */
env->prev_insn_idx = env->insn_idx;
err = prepare_func_exit(env, &env->insn_idx);
if (err)
return err;
do_print_state = true;
continue;
}
err = check_reference_leak(env);
if (err)
return err;
/* eBPF calling convetion is such that R0 is used
* to return the value from eBPF program.
* Make sure that it's readable at this time
* of bpf_exit, which means that program wrote
* something into it earlier
*/
err = check_reg_arg(env, BPF_REG_0, SRC_OP);
if (err)
return err;
if (is_pointer_value(env, BPF_REG_0)) {
verbose(env, "R0 leaks addr as return value\n");
return -EACCES;
}
err = check_return_code(env);
if (err)
return err;
process_bpf_exit:
err = pop_stack(env, &env->prev_insn_idx,
&env->insn_idx);
if (err < 0) {
if (err != -ENOENT)
return err;
break;
} else {
do_print_state = true;
continue;
}
} else {
err = check_cond_jmp_op(env, insn, &env->insn_idx);
if (err)
return err;
}
} else if (class == BPF_LD) {
u8 mode = BPF_MODE(insn->code);
if (mode == BPF_ABS || mode == BPF_IND) {
err = check_ld_abs(env, insn);
if (err)
return err;
} else if (mode == BPF_IMM) {
err = check_ld_imm(env, insn);
if (err)
return err;
env->insn_idx++;
env->insn_aux_data[env->insn_idx].seen = true;
} else {
verbose(env, "invalid BPF_LD mode\n");
return -EINVAL;
}
} else {
verbose(env, "unknown insn class %d\n", class);
return -EINVAL;
}
env->insn_idx++;
}
verbose(env, "processed %d insns (limit %d), stack depth ",
insn_processed, BPF_COMPLEXITY_LIMIT_INSNS);
for (i = 0; i < env->subprog_cnt; i++) {
u32 depth = env->subprog_info[i].stack_depth;
verbose(env, "%d", depth);
if (i + 1 < env->subprog_cnt)
verbose(env, "+");
}
verbose(env, "\n");
env->prog->aux->stack_depth = env->subprog_info[0].stack_depth;
return 0;
}
static int check_map_prealloc(struct bpf_map *map)
{
return (map->map_type != BPF_MAP_TYPE_HASH &&
map->map_type != BPF_MAP_TYPE_PERCPU_HASH &&
map->map_type != BPF_MAP_TYPE_HASH_OF_MAPS) ||
!(map->map_flags & BPF_F_NO_PREALLOC);
}
static bool is_tracing_prog_type(enum bpf_prog_type type)
{
switch (type) {
case BPF_PROG_TYPE_KPROBE:
case BPF_PROG_TYPE_TRACEPOINT:
case BPF_PROG_TYPE_PERF_EVENT:
case BPF_PROG_TYPE_RAW_TRACEPOINT:
return true;
default:
return false;
}
}
static int check_map_prog_compatibility(struct bpf_verifier_env *env,
struct bpf_map *map,
struct bpf_prog *prog)
{
/* Make sure that BPF_PROG_TYPE_PERF_EVENT programs only use
* preallocated hash maps, since doing memory allocation
* in overflow_handler can crash depending on where nmi got
* triggered.
*/
if (prog->type == BPF_PROG_TYPE_PERF_EVENT) {
if (!check_map_prealloc(map)) {
verbose(env, "perf_event programs can only use preallocated hash map\n");
return -EINVAL;
}
if (map->inner_map_meta &&
!check_map_prealloc(map->inner_map_meta)) {
verbose(env, "perf_event programs can only use preallocated inner hash map\n");
return -EINVAL;
}
}
if ((is_tracing_prog_type(prog->type) ||
prog->type == BPF_PROG_TYPE_SOCKET_FILTER) &&
map_value_has_spin_lock(map)) {
verbose(env, "tracing progs cannot use bpf_spin_lock yet\n");
return -EINVAL;
}
if ((bpf_prog_is_dev_bound(prog->aux) || bpf_map_is_dev_bound(map)) &&
!bpf_offload_prog_map_match(prog, map)) {
verbose(env, "offload device mismatch between prog and map\n");
return -EINVAL;
}
return 0;
}
static bool bpf_map_is_cgroup_storage(struct bpf_map *map)
{
return (map->map_type == BPF_MAP_TYPE_CGROUP_STORAGE ||
map->map_type == BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE);
}
/* look for pseudo eBPF instructions that access map FDs and
* replace them with actual map pointers
*/
static int replace_map_fd_with_map_ptr(struct bpf_verifier_env *env)
{
struct bpf_insn *insn = env->prog->insnsi;
int insn_cnt = env->prog->len;
int i, j, err;
err = bpf_prog_calc_tag(env->prog);
if (err)
return err;
for (i = 0; i < insn_cnt; i++, insn++) {
if (BPF_CLASS(insn->code) == BPF_LDX &&
(BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0)) {
verbose(env, "BPF_LDX uses reserved fields\n");
return -EINVAL;
}
if (BPF_CLASS(insn->code) == BPF_STX &&
((BPF_MODE(insn->code) != BPF_MEM &&
BPF_MODE(insn->code) != BPF_XADD) || insn->imm != 0)) {
verbose(env, "BPF_STX uses reserved fields\n");
return -EINVAL;
}
if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW)) {
struct bpf_map *map;
struct fd f;
if (i == insn_cnt - 1 || insn[1].code != 0 ||
insn[1].dst_reg != 0 || insn[1].src_reg != 0 ||
insn[1].off != 0) {
verbose(env, "invalid bpf_ld_imm64 insn\n");
return -EINVAL;
}
if (insn->src_reg == 0)
/* valid generic load 64-bit imm */
goto next_insn;
if (insn[0].src_reg != BPF_PSEUDO_MAP_FD ||
insn[1].imm != 0) {
verbose(env, "unrecognized bpf_ld_imm64 insn\n");
return -EINVAL;
}
f = fdget(insn[0].imm);
map = __bpf_map_get(f);
if (IS_ERR(map)) {
verbose(env, "fd %d is not pointing to valid bpf_map\n",
insn[0].imm);
return PTR_ERR(map);
}
err = check_map_prog_compatibility(env, map, env->prog);
if (err) {
fdput(f);
return err;
}
/* store map pointer inside BPF_LD_IMM64 instruction */
insn[0].imm = (u32) (unsigned long) map;
insn[1].imm = ((u64) (unsigned long) map) >> 32;
/* check whether we recorded this map already */
for (j = 0; j < env->used_map_cnt; j++)
if (env->used_maps[j] == map) {
fdput(f);
goto next_insn;
}
if (env->used_map_cnt >= MAX_USED_MAPS) {
fdput(f);
return -E2BIG;
}
/* hold the map. If the program is rejected by verifier,
* the map will be released by release_maps() or it
* will be used by the valid program until it's unloaded
* and all maps are released in free_used_maps()
*/
map = bpf_map_inc(map, false);
if (IS_ERR(map)) {
fdput(f);
return PTR_ERR(map);
}
env->used_maps[env->used_map_cnt++] = map;
if (bpf_map_is_cgroup_storage(map) &&
bpf_cgroup_storage_assign(env->prog, map)) {
verbose(env, "only one cgroup storage of each type is allowed\n");
fdput(f);
return -EBUSY;
}
fdput(f);
next_insn:
insn++;
i++;
continue;
}
/* Basic sanity check before we invest more work here. */
if (!bpf_opcode_in_insntable(insn->code)) {
verbose(env, "unknown opcode %02x\n", insn->code);
return -EINVAL;
}
}
/* now all pseudo BPF_LD_IMM64 instructions load valid
* 'struct bpf_map *' into a register instead of user map_fd.
* These pointers will be used later by verifier to validate map access.
*/
return 0;
}
/* drop refcnt of maps used by the rejected program */
static void release_maps(struct bpf_verifier_env *env)
{
enum bpf_cgroup_storage_type stype;
int i;
for_each_cgroup_storage_type(stype) {
if (!env->prog->aux->cgroup_storage[stype])
continue;
bpf_cgroup_storage_release(env->prog,
env->prog->aux->cgroup_storage[stype]);
}
for (i = 0; i < env->used_map_cnt; i++)
bpf_map_put(env->used_maps[i]);
}
/* convert pseudo BPF_LD_IMM64 into generic BPF_LD_IMM64 */
static void convert_pseudo_ld_imm64(struct bpf_verifier_env *env)
{
struct bpf_insn *insn = env->prog->insnsi;
int insn_cnt = env->prog->len;
int i;
for (i = 0; i < insn_cnt; i++, insn++)
if (insn->code == (BPF_LD | BPF_IMM | BPF_DW))
insn->src_reg = 0;
}
/* single env->prog->insni[off] instruction was replaced with the range
* insni[off, off + cnt). Adjust corresponding insn_aux_data by copying
* [0, off) and [off, end) to new locations, so the patched range stays zero
*/
static int adjust_insn_aux_data(struct bpf_verifier_env *env, u32 prog_len,
u32 off, u32 cnt)
{
struct bpf_insn_aux_data *new_data, *old_data = env->insn_aux_data;
int i;
if (cnt == 1)
return 0;
new_data = vzalloc(array_size(prog_len,
sizeof(struct bpf_insn_aux_data)));
if (!new_data)
return -ENOMEM;
memcpy(new_data, old_data, sizeof(struct bpf_insn_aux_data) * off);
memcpy(new_data + off + cnt - 1, old_data + off,
sizeof(struct bpf_insn_aux_data) * (prog_len - off - cnt + 1));
for (i = off; i < off + cnt - 1; i++)
new_data[i].seen = true;
env->insn_aux_data = new_data;
vfree(old_data);
return 0;
}
static void adjust_subprog_starts(struct bpf_verifier_env *env, u32 off, u32 len)
{
int i;
if (len == 1)
return;
/* NOTE: fake 'exit' subprog should be updated as well. */
for (i = 0; i <= env->subprog_cnt; i++) {
if (env->subprog_info[i].start <= off)
continue;
env->subprog_info[i].start += len - 1;
}
}
static struct bpf_prog *bpf_patch_insn_data(struct bpf_verifier_env *env, u32 off,
const struct bpf_insn *patch, u32 len)
{
struct bpf_prog *new_prog;
new_prog = bpf_patch_insn_single(env->prog, off, patch, len);
if (!new_prog)
return NULL;
if (adjust_insn_aux_data(env, new_prog->len, off, len))
return NULL;
adjust_subprog_starts(env, off, len);
return new_prog;
}
static int adjust_subprog_starts_after_remove(struct bpf_verifier_env *env,
u32 off, u32 cnt)
{
int i, j;
/* find first prog starting at or after off (first to remove) */
for (i = 0; i < env->subprog_cnt; i++)
if (env->subprog_info[i].start >= off)
break;
/* find first prog starting at or after off + cnt (first to stay) */
for (j = i; j < env->subprog_cnt; j++)
if (env->subprog_info[j].start >= off + cnt)
break;
/* if j doesn't start exactly at off + cnt, we are just removing
* the front of previous prog
*/
if (env->subprog_info[j].start != off + cnt)
j--;
if (j > i) {
struct bpf_prog_aux *aux = env->prog->aux;
int move;
/* move fake 'exit' subprog as well */
move = env->subprog_cnt + 1 - j;
memmove(env->subprog_info + i,
env->subprog_info + j,
sizeof(*env->subprog_info) * move);
env->subprog_cnt -= j - i;
/* remove func_info */
if (aux->func_info) {
move = aux->func_info_cnt - j;
memmove(aux->func_info + i,
aux->func_info + j,
sizeof(*aux->func_info) * move);
aux->func_info_cnt -= j - i;
/* func_info->insn_off is set after all code rewrites,
* in adjust_btf_func() - no need to adjust
*/
}
} else {
/* convert i from "first prog to remove" to "first to adjust" */
if (env->subprog_info[i].start == off)
i++;
}
/* update fake 'exit' subprog as well */
for (; i <= env->subprog_cnt; i++)
env->subprog_info[i].start -= cnt;
return 0;
}
static int bpf_adj_linfo_after_remove(struct bpf_verifier_env *env, u32 off,
u32 cnt)
{
struct bpf_prog *prog = env->prog;
u32 i, l_off, l_cnt, nr_linfo;
struct bpf_line_info *linfo;
nr_linfo = prog->aux->nr_linfo;
if (!nr_linfo)
return 0;
linfo = prog->aux->linfo;
/* find first line info to remove, count lines to be removed */
for (i = 0; i < nr_linfo; i++)
if (linfo[i].insn_off >= off)
break;
l_off = i;
l_cnt = 0;
for (; i < nr_linfo; i++)
if (linfo[i].insn_off < off + cnt)
l_cnt++;
else
break;
/* First live insn doesn't match first live linfo, it needs to "inherit"
* last removed linfo. prog is already modified, so prog->len == off
* means no live instructions after (tail of the program was removed).
*/
if (prog->len != off && l_cnt &&
(i == nr_linfo || linfo[i].insn_off != off + cnt)) {
l_cnt--;
linfo[--i].insn_off = off + cnt;
}
/* remove the line info which refer to the removed instructions */
if (l_cnt) {
memmove(linfo + l_off, linfo + i,
sizeof(*linfo) * (nr_linfo - i));
prog->aux->nr_linfo -= l_cnt;
nr_linfo = prog->aux->nr_linfo;
}
/* pull all linfo[i].insn_off >= off + cnt in by cnt */
for (i = l_off; i < nr_linfo; i++)
linfo[i].insn_off -= cnt;
/* fix up all subprogs (incl. 'exit') which start >= off */
for (i = 0; i <= env->subprog_cnt; i++)
if (env->subprog_info[i].linfo_idx > l_off) {
/* program may have started in the removed region but
* may not be fully removed
*/
if (env->subprog_info[i].linfo_idx >= l_off + l_cnt)
env->subprog_info[i].linfo_idx -= l_cnt;
else
env->subprog_info[i].linfo_idx = l_off;
}
return 0;
}
static int verifier_remove_insns(struct bpf_verifier_env *env, u32 off, u32 cnt)
{
struct bpf_insn_aux_data *aux_data = env->insn_aux_data;
unsigned int orig_prog_len = env->prog->len;
int err;
if (bpf_prog_is_dev_bound(env->prog->aux))
bpf_prog_offload_remove_insns(env, off, cnt);
err = bpf_remove_insns(env->prog, off, cnt);
if (err)
return err;
err = adjust_subprog_starts_after_remove(env, off, cnt);
if (err)
return err;
err = bpf_adj_linfo_after_remove(env, off, cnt);
if (err)
return err;
memmove(aux_data + off, aux_data + off + cnt,
sizeof(*aux_data) * (orig_prog_len - off - cnt));
return 0;
}
/* The verifier does more data flow analysis than llvm and will not
* explore branches that are dead at run time. Malicious programs can
* have dead code too. Therefore replace all dead at-run-time code
* with 'ja -1'.
*
* Just nops are not optimal, e.g. if they would sit at the end of the
* program and through another bug we would manage to jump there, then
* we'd execute beyond program memory otherwise. Returning exception
* code also wouldn't work since we can have subprogs where the dead
* code could be located.
*/
static void sanitize_dead_code(struct bpf_verifier_env *env)
{
struct bpf_insn_aux_data *aux_data = env->insn_aux_data;
struct bpf_insn trap = BPF_JMP_IMM(BPF_JA, 0, 0, -1);
struct bpf_insn *insn = env->prog->insnsi;
const int insn_cnt = env->prog->len;
int i;
for (i = 0; i < insn_cnt; i++) {
if (aux_data[i].seen)
continue;
memcpy(insn + i, &trap, sizeof(trap));
}
}
static bool insn_is_cond_jump(u8 code)
{
u8 op;
if (BPF_CLASS(code) == BPF_JMP32)
return true;
if (BPF_CLASS(code) != BPF_JMP)
return false;
op = BPF_OP(code);
return op != BPF_JA && op != BPF_EXIT && op != BPF_CALL;
}
static void opt_hard_wire_dead_code_branches(struct bpf_verifier_env *env)
{
struct bpf_insn_aux_data *aux_data = env->insn_aux_data;
struct bpf_insn ja = BPF_JMP_IMM(BPF_JA, 0, 0, 0);
struct bpf_insn *insn = env->prog->insnsi;
const int insn_cnt = env->prog->len;
int i;
for (i = 0; i < insn_cnt; i++, insn++) {
if (!insn_is_cond_jump(insn->code))
continue;
if (!aux_data[i + 1].seen)
ja.off = insn->off;
else if (!aux_data[i + 1 + insn->off].seen)
ja.off = 0;
else
continue;
if (bpf_prog_is_dev_bound(env->prog->aux))
bpf_prog_offload_replace_insn(env, i, &ja);
memcpy(insn, &ja, sizeof(ja));
}
}
static int opt_remove_dead_code(struct bpf_verifier_env *env)
{
struct bpf_insn_aux_data *aux_data = env->insn_aux_data;
int insn_cnt = env->prog->len;
int i, err;
for (i = 0; i < insn_cnt; i++) {
int j;
j = 0;
while (i + j < insn_cnt && !aux_data[i + j].seen)
j++;
if (!j)
continue;
err = verifier_remove_insns(env, i, j);
if (err)
return err;
insn_cnt = env->prog->len;
}
return 0;
}
static int opt_remove_nops(struct bpf_verifier_env *env)
{
const struct bpf_insn ja = BPF_JMP_IMM(BPF_JA, 0, 0, 0);
struct bpf_insn *insn = env->prog->insnsi;
int insn_cnt = env->prog->len;
int i, err;
for (i = 0; i < insn_cnt; i++) {
if (memcmp(&insn[i], &ja, sizeof(ja)))
continue;
err = verifier_remove_insns(env, i, 1);
if (err)
return err;
insn_cnt--;
i--;
}
return 0;
}
/* convert load instructions that access fields of a context type into a
* sequence of instructions that access fields of the underlying structure:
* struct __sk_buff -> struct sk_buff
* struct bpf_sock_ops -> struct sock
*/
static int convert_ctx_accesses(struct bpf_verifier_env *env)
{
const struct bpf_verifier_ops *ops = env->ops;
int i, cnt, size, ctx_field_size, delta = 0;
const int insn_cnt = env->prog->len;
struct bpf_insn insn_buf[16], *insn;
u32 target_size, size_default, off;
struct bpf_prog *new_prog;
enum bpf_access_type type;
bool is_narrower_load;
if (ops->gen_prologue || env->seen_direct_write) {
if (!ops->gen_prologue) {
verbose(env, "bpf verifier is misconfigured\n");
return -EINVAL;
}
cnt = ops->gen_prologue(insn_buf, env->seen_direct_write,
env->prog);
if (cnt >= ARRAY_SIZE(insn_buf)) {
verbose(env, "bpf verifier is misconfigured\n");
return -EINVAL;
} else if (cnt) {
new_prog = bpf_patch_insn_data(env, 0, insn_buf, cnt);
if (!new_prog)
return -ENOMEM;
env->prog = new_prog;
delta += cnt - 1;
}
}
if (bpf_prog_is_dev_bound(env->prog->aux))
return 0;
insn = env->prog->insnsi + delta;
for (i = 0; i < insn_cnt; i++, insn++) {
bpf_convert_ctx_access_t convert_ctx_access;
if (insn->code == (BPF_LDX | BPF_MEM | BPF_B) ||
insn->code == (BPF_LDX | BPF_MEM | BPF_H) ||
insn->code == (BPF_LDX | BPF_MEM | BPF_W) ||
insn->code == (BPF_LDX | BPF_MEM | BPF_DW))
type = BPF_READ;
else if (insn->code == (BPF_STX | BPF_MEM | BPF_B) ||
insn->code == (BPF_STX | BPF_MEM | BPF_H) ||
insn->code == (BPF_STX | BPF_MEM | BPF_W) ||
insn->code == (BPF_STX | BPF_MEM | BPF_DW))
type = BPF_WRITE;
else
continue;
if (type == BPF_WRITE &&
env->insn_aux_data[i + delta].sanitize_stack_off) {
struct bpf_insn patch[] = {
/* Sanitize suspicious stack slot with zero.
* There are no memory dependencies for this store,
* since it's only using frame pointer and immediate
* constant of zero
*/
BPF_ST_MEM(BPF_DW, BPF_REG_FP,
env->insn_aux_data[i + delta].sanitize_stack_off,
0),
/* the original STX instruction will immediately
* overwrite the same stack slot with appropriate value
*/
*insn,
};
cnt = ARRAY_SIZE(patch);
new_prog = bpf_patch_insn_data(env, i + delta, patch, cnt);
if (!new_prog)
return -ENOMEM;
delta += cnt - 1;
env->prog = new_prog;
insn = new_prog->insnsi + i + delta;
continue;
}
switch (env->insn_aux_data[i + delta].ptr_type) {
case PTR_TO_CTX:
if (!ops->convert_ctx_access)
continue;
convert_ctx_access = ops->convert_ctx_access;
break;
case PTR_TO_SOCKET:
case PTR_TO_SOCK_COMMON:
convert_ctx_access = bpf_sock_convert_ctx_access;
break;
case PTR_TO_TCP_SOCK:
convert_ctx_access = bpf_tcp_sock_convert_ctx_access;
break;
default:
continue;
}
ctx_field_size = env->insn_aux_data[i + delta].ctx_field_size;
size = BPF_LDST_BYTES(insn);
/* If the read access is a narrower load of the field,
* convert to a 4/8-byte load, to minimum program type specific
* convert_ctx_access changes. If conversion is successful,
* we will apply proper mask to the result.
*/
is_narrower_load = size < ctx_field_size;
size_default = bpf_ctx_off_adjust_machine(ctx_field_size);
off = insn->off;
if (is_narrower_load) {
u8 size_code;
if (type == BPF_WRITE) {
verbose(env, "bpf verifier narrow ctx access misconfigured\n");
return -EINVAL;
}
size_code = BPF_H;
if (ctx_field_size == 4)
size_code = BPF_W;
else if (ctx_field_size == 8)
size_code = BPF_DW;
insn->off = off & ~(size_default - 1);
insn->code = BPF_LDX | BPF_MEM | size_code;
}
target_size = 0;
cnt = convert_ctx_access(type, insn, insn_buf, env->prog,
&target_size);
if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf) ||
(ctx_field_size && !target_size)) {
verbose(env, "bpf verifier is misconfigured\n");
return -EINVAL;
}
if (is_narrower_load && size < target_size) {
u8 shift = (off & (size_default - 1)) * 8;
if (ctx_field_size <= 4) {
if (shift)
insn_buf[cnt++] = BPF_ALU32_IMM(BPF_RSH,
insn->dst_reg,
shift);
insn_buf[cnt++] = BPF_ALU32_IMM(BPF_AND, insn->dst_reg,
(1 << size * 8) - 1);
} else {
if (shift)
insn_buf[cnt++] = BPF_ALU64_IMM(BPF_RSH,
insn->dst_reg,
shift);
insn_buf[cnt++] = BPF_ALU64_IMM(BPF_AND, insn->dst_reg,
(1 << size * 8) - 1);
}
}
new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
if (!new_prog)
return -ENOMEM;
delta += cnt - 1;
/* keep walking new program and skip insns we just inserted */
env->prog = new_prog;
insn = new_prog->insnsi + i + delta;
}
return 0;
}
static int jit_subprogs(struct bpf_verifier_env *env)
{
struct bpf_prog *prog = env->prog, **func, *tmp;
int i, j, subprog_start, subprog_end = 0, len, subprog;
struct bpf_insn *insn;
void *old_bpf_func;
int err;
if (env->subprog_cnt <= 1)
return 0;
for (i = 0, insn = prog->insnsi; i < prog->len; i++, insn++) {
if (insn->code != (BPF_JMP | BPF_CALL) ||
insn->src_reg != BPF_PSEUDO_CALL)
continue;
/* Upon error here we cannot fall back to interpreter but
* need a hard reject of the program. Thus -EFAULT is
* propagated in any case.
*/
subprog = find_subprog(env, i + insn->imm + 1);
if (subprog < 0) {
WARN_ONCE(1, "verifier bug. No program starts at insn %d\n",
i + insn->imm + 1);
return -EFAULT;
}
/* temporarily remember subprog id inside insn instead of
* aux_data, since next loop will split up all insns into funcs
*/
insn->off = subprog;
/* remember original imm in case JIT fails and fallback
* to interpreter will be needed
*/
env->insn_aux_data[i].call_imm = insn->imm;
/* point imm to __bpf_call_base+1 from JITs point of view */
insn->imm = 1;
}
err = bpf_prog_alloc_jited_linfo(prog);
if (err)
goto out_undo_insn;
err = -ENOMEM;
func = kcalloc(env->subprog_cnt, sizeof(prog), GFP_KERNEL);
if (!func)
goto out_undo_insn;
for (i = 0; i < env->subprog_cnt; i++) {
subprog_start = subprog_end;
subprog_end = env->subprog_info[i + 1].start;
len = subprog_end - subprog_start;
/* BPF_PROG_RUN doesn't call subprogs directly,
* hence main prog stats include the runtime of subprogs.
* subprogs don't have IDs and not reachable via prog_get_next_id
* func[i]->aux->stats will never be accessed and stays NULL
*/
func[i] = bpf_prog_alloc_no_stats(bpf_prog_size(len), GFP_USER);
if (!func[i])
goto out_free;
memcpy(func[i]->insnsi, &prog->insnsi[subprog_start],
len * sizeof(struct bpf_insn));
func[i]->type = prog->type;
func[i]->len = len;
if (bpf_prog_calc_tag(func[i]))
goto out_free;
func[i]->is_func = 1;
func[i]->aux->func_idx = i;
/* the btf and func_info will be freed only at prog->aux */
func[i]->aux->btf = prog->aux->btf;
func[i]->aux->func_info = prog->aux->func_info;
/* Use bpf_prog_F_tag to indicate functions in stack traces.
* Long term would need debug info to populate names
*/
func[i]->aux->name[0] = 'F';
func[i]->aux->stack_depth = env->subprog_info[i].stack_depth;
func[i]->jit_requested = 1;
func[i]->aux->linfo = prog->aux->linfo;
func[i]->aux->nr_linfo = prog->aux->nr_linfo;
func[i]->aux->jited_linfo = prog->aux->jited_linfo;
func[i]->aux->linfo_idx = env->subprog_info[i].linfo_idx;
func[i] = bpf_int_jit_compile(func[i]);
if (!func[i]->jited) {
err = -ENOTSUPP;
goto out_free;
}
cond_resched();
}
/* at this point all bpf functions were successfully JITed
* now populate all bpf_calls with correct addresses and
* run last pass of JIT
*/
for (i = 0; i < env->subprog_cnt; i++) {
insn = func[i]->insnsi;
for (j = 0; j < func[i]->len; j++, insn++) {
if (insn->code != (BPF_JMP | BPF_CALL) ||
insn->src_reg != BPF_PSEUDO_CALL)
continue;
subprog = insn->off;
insn->imm = (u64 (*)(u64, u64, u64, u64, u64))
func[subprog]->bpf_func -
__bpf_call_base;
}
/* we use the aux data to keep a list of the start addresses
* of the JITed images for each function in the program
*
* for some architectures, such as powerpc64, the imm field
* might not be large enough to hold the offset of the start
* address of the callee's JITed image from __bpf_call_base
*
* in such cases, we can lookup the start address of a callee
* by using its subprog id, available from the off field of
* the call instruction, as an index for this list
*/
func[i]->aux->func = func;
func[i]->aux->func_cnt = env->subprog_cnt;
}
for (i = 0; i < env->subprog_cnt; i++) {
old_bpf_func = func[i]->bpf_func;
tmp = bpf_int_jit_compile(func[i]);
if (tmp != func[i] || func[i]->bpf_func != old_bpf_func) {
verbose(env, "JIT doesn't support bpf-to-bpf calls\n");
err = -ENOTSUPP;
goto out_free;
}
cond_resched();
}
/* finally lock prog and jit images for all functions and
* populate kallsysm
*/
for (i = 0; i < env->subprog_cnt; i++) {
bpf_prog_lock_ro(func[i]);
bpf_prog_kallsyms_add(func[i]);
}
/* Last step: make now unused interpreter insns from main
* prog consistent for later dump requests, so they can
* later look the same as if they were interpreted only.
*/
for (i = 0, insn = prog->insnsi; i < prog->len; i++, insn++) {
if (insn->code != (BPF_JMP | BPF_CALL) ||
insn->src_reg != BPF_PSEUDO_CALL)
continue;
insn->off = env->insn_aux_data[i].call_imm;
subprog = find_subprog(env, i + insn->off + 1);
insn->imm = subprog;
}
prog->jited = 1;
prog->bpf_func = func[0]->bpf_func;
prog->aux->func = func;
prog->aux->func_cnt = env->subprog_cnt;
bpf_prog_free_unused_jited_linfo(prog);
return 0;
out_free:
for (i = 0; i < env->subprog_cnt; i++)
if (func[i])
bpf_jit_free(func[i]);
kfree(func);
out_undo_insn:
/* cleanup main prog to be interpreted */
prog->jit_requested = 0;
for (i = 0, insn = prog->insnsi; i < prog->len; i++, insn++) {
if (insn->code != (BPF_JMP | BPF_CALL) ||
insn->src_reg != BPF_PSEUDO_CALL)
continue;
insn->off = 0;
insn->imm = env->insn_aux_data[i].call_imm;
}
bpf_prog_free_jited_linfo(prog);
return err;
}
static int fixup_call_args(struct bpf_verifier_env *env)
{
#ifndef CONFIG_BPF_JIT_ALWAYS_ON
struct bpf_prog *prog = env->prog;
struct bpf_insn *insn = prog->insnsi;
int i, depth;
#endif
int err = 0;
if (env->prog->jit_requested &&
!bpf_prog_is_dev_bound(env->prog->aux)) {
err = jit_subprogs(env);
if (err == 0)
return 0;
if (err == -EFAULT)
return err;
}
#ifndef CONFIG_BPF_JIT_ALWAYS_ON
for (i = 0; i < prog->len; i++, insn++) {
if (insn->code != (BPF_JMP | BPF_CALL) ||
insn->src_reg != BPF_PSEUDO_CALL)
continue;
depth = get_callee_stack_depth(env, insn, i);
if (depth < 0)
return depth;
bpf_patch_call_args(insn, depth);
}
err = 0;
#endif
return err;
}
/* fixup insn->imm field of bpf_call instructions
* and inline eligible helpers as explicit sequence of BPF instructions
*
* this function is called after eBPF program passed verification
*/
static int fixup_bpf_calls(struct bpf_verifier_env *env)
{
struct bpf_prog *prog = env->prog;
struct bpf_insn *insn = prog->insnsi;
const struct bpf_func_proto *fn;
const int insn_cnt = prog->len;
const struct bpf_map_ops *ops;
struct bpf_insn_aux_data *aux;
struct bpf_insn insn_buf[16];
struct bpf_prog *new_prog;
struct bpf_map *map_ptr;
int i, cnt, delta = 0;
for (i = 0; i < insn_cnt; i++, insn++) {
if (insn->code == (BPF_ALU64 | BPF_MOD | BPF_X) ||
insn->code == (BPF_ALU64 | BPF_DIV | BPF_X) ||
insn->code == (BPF_ALU | BPF_MOD | BPF_X) ||
insn->code == (BPF_ALU | BPF_DIV | BPF_X)) {
bool is64 = BPF_CLASS(insn->code) == BPF_ALU64;
struct bpf_insn mask_and_div[] = {
BPF_MOV32_REG(insn->src_reg, insn->src_reg),
/* Rx div 0 -> 0 */
BPF_JMP_IMM(BPF_JNE, insn->src_reg, 0, 2),
BPF_ALU32_REG(BPF_XOR, insn->dst_reg, insn->dst_reg),
BPF_JMP_IMM(BPF_JA, 0, 0, 1),
*insn,
};
struct bpf_insn mask_and_mod[] = {
BPF_MOV32_REG(insn->src_reg, insn->src_reg),
/* Rx mod 0 -> Rx */
BPF_JMP_IMM(BPF_JEQ, insn->src_reg, 0, 1),
*insn,
};
struct bpf_insn *patchlet;
if (insn->code == (BPF_ALU64 | BPF_DIV | BPF_X) ||
insn->code == (BPF_ALU | BPF_DIV | BPF_X)) {
patchlet = mask_and_div + (is64 ? 1 : 0);
cnt = ARRAY_SIZE(mask_and_div) - (is64 ? 1 : 0);
} else {
patchlet = mask_and_mod + (is64 ? 1 : 0);
cnt = ARRAY_SIZE(mask_and_mod) - (is64 ? 1 : 0);
}
new_prog = bpf_patch_insn_data(env, i + delta, patchlet, cnt);
if (!new_prog)
return -ENOMEM;
delta += cnt - 1;
env->prog = prog = new_prog;
insn = new_prog->insnsi + i + delta;
continue;
}
if (BPF_CLASS(insn->code) == BPF_LD &&
(BPF_MODE(insn->code) == BPF_ABS ||
BPF_MODE(insn->code) == BPF_IND)) {
cnt = env->ops->gen_ld_abs(insn, insn_buf);
if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) {
verbose(env, "bpf verifier is misconfigured\n");
return -EINVAL;
}
new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
if (!new_prog)
return -ENOMEM;
delta += cnt - 1;
env->prog = prog = new_prog;
insn = new_prog->insnsi + i + delta;
continue;
}
if (insn->code == (BPF_ALU64 | BPF_ADD | BPF_X) ||
insn->code == (BPF_ALU64 | BPF_SUB | BPF_X)) {
const u8 code_add = BPF_ALU64 | BPF_ADD | BPF_X;
const u8 code_sub = BPF_ALU64 | BPF_SUB | BPF_X;
struct bpf_insn insn_buf[16];
struct bpf_insn *patch = &insn_buf[0];
bool issrc, isneg;
u32 off_reg;
aux = &env->insn_aux_data[i + delta];
if (!aux->alu_state ||
aux->alu_state == BPF_ALU_NON_POINTER)
continue;
isneg = aux->alu_state & BPF_ALU_NEG_VALUE;
issrc = (aux->alu_state & BPF_ALU_SANITIZE) ==
BPF_ALU_SANITIZE_SRC;
off_reg = issrc ? insn->src_reg : insn->dst_reg;
if (isneg)
*patch++ = BPF_ALU64_IMM(BPF_MUL, off_reg, -1);
*patch++ = BPF_MOV32_IMM(BPF_REG_AX, aux->alu_limit - 1);
*patch++ = BPF_ALU64_REG(BPF_SUB, BPF_REG_AX, off_reg);
*patch++ = BPF_ALU64_REG(BPF_OR, BPF_REG_AX, off_reg);
*patch++ = BPF_ALU64_IMM(BPF_NEG, BPF_REG_AX, 0);
*patch++ = BPF_ALU64_IMM(BPF_ARSH, BPF_REG_AX, 63);
if (issrc) {
*patch++ = BPF_ALU64_REG(BPF_AND, BPF_REG_AX,
off_reg);
insn->src_reg = BPF_REG_AX;
} else {
*patch++ = BPF_ALU64_REG(BPF_AND, off_reg,
BPF_REG_AX);
}
if (isneg)
insn->code = insn->code == code_add ?
code_sub : code_add;
*patch++ = *insn;
if (issrc && isneg)
*patch++ = BPF_ALU64_IMM(BPF_MUL, off_reg, -1);
cnt = patch - insn_buf;
new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
if (!new_prog)
return -ENOMEM;
delta += cnt - 1;
env->prog = prog = new_prog;
insn = new_prog->insnsi + i + delta;
continue;
}
if (insn->code != (BPF_JMP | BPF_CALL))
continue;
if (insn->src_reg == BPF_PSEUDO_CALL)
continue;
if (insn->imm == BPF_FUNC_get_route_realm)
prog->dst_needed = 1;
if (insn->imm == BPF_FUNC_get_prandom_u32)
bpf_user_rnd_init_once();
if (insn->imm == BPF_FUNC_override_return)
prog->kprobe_override = 1;
if (insn->imm == BPF_FUNC_tail_call) {
/* If we tail call into other programs, we
* cannot make any assumptions since they can
* be replaced dynamically during runtime in
* the program array.
*/
prog->cb_access = 1;
env->prog->aux->stack_depth = MAX_BPF_STACK;
env->prog->aux->max_pkt_offset = MAX_PACKET_OFF;
/* mark bpf_tail_call as different opcode to avoid
* conditional branch in the interpeter for every normal
* call and to prevent accidental JITing by JIT compiler
* that doesn't support bpf_tail_call yet
*/
insn->imm = 0;
insn->code = BPF_JMP | BPF_TAIL_CALL;
aux = &env->insn_aux_data[i + delta];
if (!bpf_map_ptr_unpriv(aux))
continue;
/* instead of changing every JIT dealing with tail_call
* emit two extra insns:
* if (index >= max_entries) goto out;
* index &= array->index_mask;
* to avoid out-of-bounds cpu speculation
*/
if (bpf_map_ptr_poisoned(aux)) {
verbose(env, "tail_call abusing map_ptr\n");
return -EINVAL;
}
map_ptr = BPF_MAP_PTR(aux->map_state);
insn_buf[0] = BPF_JMP_IMM(BPF_JGE, BPF_REG_3,
map_ptr->max_entries, 2);
insn_buf[1] = BPF_ALU32_IMM(BPF_AND, BPF_REG_3,
container_of(map_ptr,
struct bpf_array,
map)->index_mask);
insn_buf[2] = *insn;
cnt = 3;
new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
if (!new_prog)
return -ENOMEM;
delta += cnt - 1;
env->prog = prog = new_prog;
insn = new_prog->insnsi + i + delta;
continue;
}
/* BPF_EMIT_CALL() assumptions in some of the map_gen_lookup
* and other inlining handlers are currently limited to 64 bit
* only.
*/
if (prog->jit_requested && BITS_PER_LONG == 64 &&
(insn->imm == BPF_FUNC_map_lookup_elem ||
insn->imm == BPF_FUNC_map_update_elem ||
insn->imm == BPF_FUNC_map_delete_elem ||
insn->imm == BPF_FUNC_map_push_elem ||
insn->imm == BPF_FUNC_map_pop_elem ||
insn->imm == BPF_FUNC_map_peek_elem)) {
aux = &env->insn_aux_data[i + delta];
if (bpf_map_ptr_poisoned(aux))
goto patch_call_imm;
map_ptr = BPF_MAP_PTR(aux->map_state);
ops = map_ptr->ops;
if (insn->imm == BPF_FUNC_map_lookup_elem &&
ops->map_gen_lookup) {
cnt = ops->map_gen_lookup(map_ptr, insn_buf);
if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) {
verbose(env, "bpf verifier is misconfigured\n");
return -EINVAL;
}
new_prog = bpf_patch_insn_data(env, i + delta,
insn_buf, cnt);
if (!new_prog)
return -ENOMEM;
delta += cnt - 1;
env->prog = prog = new_prog;
insn = new_prog->insnsi + i + delta;
continue;
}
BUILD_BUG_ON(!__same_type(ops->map_lookup_elem,
(void *(*)(struct bpf_map *map, void *key))NULL));
BUILD_BUG_ON(!__same_type(ops->map_delete_elem,
(int (*)(struct bpf_map *map, void *key))NULL));
BUILD_BUG_ON(!__same_type(ops->map_update_elem,
(int (*)(struct bpf_map *map, void *key, void *value,
u64 flags))NULL));
BUILD_BUG_ON(!__same_type(ops->map_push_elem,
(int (*)(struct bpf_map *map, void *value,
u64 flags))NULL));
BUILD_BUG_ON(!__same_type(ops->map_pop_elem,
(int (*)(struct bpf_map *map, void *value))NULL));
BUILD_BUG_ON(!__same_type(ops->map_peek_elem,
(int (*)(struct bpf_map *map, void *value))NULL));
switch (insn->imm) {
case BPF_FUNC_map_lookup_elem:
insn->imm = BPF_CAST_CALL(ops->map_lookup_elem) -
__bpf_call_base;
continue;
case BPF_FUNC_map_update_elem:
insn->imm = BPF_CAST_CALL(ops->map_update_elem) -
__bpf_call_base;
continue;
case BPF_FUNC_map_delete_elem:
insn->imm = BPF_CAST_CALL(ops->map_delete_elem) -
__bpf_call_base;
continue;
case BPF_FUNC_map_push_elem:
insn->imm = BPF_CAST_CALL(ops->map_push_elem) -
__bpf_call_base;
continue;
case BPF_FUNC_map_pop_elem:
insn->imm = BPF_CAST_CALL(ops->map_pop_elem) -
__bpf_call_base;
continue;
case BPF_FUNC_map_peek_elem:
insn->imm = BPF_CAST_CALL(ops->map_peek_elem) -
__bpf_call_base;
continue;
}
goto patch_call_imm;
}
patch_call_imm:
fn = env->ops->get_func_proto(insn->imm, env->prog);
/* all functions that have prototype and verifier allowed
* programs to call them, must be real in-kernel functions
*/
if (!fn->func) {
verbose(env,
"kernel subsystem misconfigured func %s#%d\n",
func_id_name(insn->imm), insn->imm);
return -EFAULT;
}
insn->imm = fn->func - __bpf_call_base;
}
return 0;
}
static void free_states(struct bpf_verifier_env *env)
{
struct bpf_verifier_state_list *sl, *sln;
int i;
if (!env->explored_states)
return;
for (i = 0; i < env->prog->len; i++) {
sl = env->explored_states[i];
if (sl)
while (sl != STATE_LIST_MARK) {
sln = sl->next;
free_verifier_state(&sl->state, false);
kfree(sl);
sl = sln;
}
}
kfree(env->explored_states);
}
int bpf_check(struct bpf_prog **prog, union bpf_attr *attr,
union bpf_attr __user *uattr)
{
struct bpf_verifier_env *env;
struct bpf_verifier_log *log;
int i, len, ret = -EINVAL;
bool is_priv;
/* no program is valid */
if (ARRAY_SIZE(bpf_verifier_ops) == 0)
return -EINVAL;
/* 'struct bpf_verifier_env' can be global, but since it's not small,
* allocate/free it every time bpf_check() is called
*/
env = kzalloc(sizeof(struct bpf_verifier_env), GFP_KERNEL);
if (!env)
return -ENOMEM;
log = &env->log;
len = (*prog)->len;
env->insn_aux_data =
vzalloc(array_size(sizeof(struct bpf_insn_aux_data), len));
ret = -ENOMEM;
if (!env->insn_aux_data)
goto err_free_env;
for (i = 0; i < len; i++)
env->insn_aux_data[i].orig_idx = i;
env->prog = *prog;
env->ops = bpf_verifier_ops[env->prog->type];
/* grab the mutex to protect few globals used by verifier */
mutex_lock(&bpf_verifier_lock);
if (attr->log_level || attr->log_buf || attr->log_size) {
/* user requested verbose verifier output
* and supplied buffer to store the verification trace
*/
log->level = attr->log_level;
log->ubuf = (char __user *) (unsigned long) attr->log_buf;
log->len_total = attr->log_size;
ret = -EINVAL;
/* log attributes have to be sane */
if (log->len_total < 128 || log->len_total > UINT_MAX >> 8 ||
!log->level || !log->ubuf)
goto err_unlock;
}
env->strict_alignment = !!(attr->prog_flags & BPF_F_STRICT_ALIGNMENT);
if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
env->strict_alignment = true;
if (attr->prog_flags & BPF_F_ANY_ALIGNMENT)
env->strict_alignment = false;
is_priv = capable(CAP_SYS_ADMIN);
env->allow_ptr_leaks = is_priv;
ret = replace_map_fd_with_map_ptr(env);
if (ret < 0)
goto skip_full_check;
if (bpf_prog_is_dev_bound(env->prog->aux)) {
ret = bpf_prog_offload_verifier_prep(env->prog);
if (ret)
goto skip_full_check;
}
env->explored_states = kcalloc(env->prog->len,
sizeof(struct bpf_verifier_state_list *),
GFP_USER);
ret = -ENOMEM;
if (!env->explored_states)
goto skip_full_check;
ret = check_subprogs(env);
if (ret < 0)
goto skip_full_check;
ret = check_btf_info(env, attr, uattr);
if (ret < 0)
goto skip_full_check;
ret = check_cfg(env);
if (ret < 0)
goto skip_full_check;
ret = do_check(env);
if (env->cur_state) {
free_verifier_state(env->cur_state, true);
env->cur_state = NULL;
}
if (ret == 0 && bpf_prog_is_dev_bound(env->prog->aux))
ret = bpf_prog_offload_finalize(env);
skip_full_check:
while (!pop_stack(env, NULL, NULL));
free_states(env);
if (ret == 0)
ret = check_max_stack_depth(env);
/* instruction rewrites happen after this point */
if (is_priv) {
if (ret == 0)
opt_hard_wire_dead_code_branches(env);
if (ret == 0)
ret = opt_remove_dead_code(env);
if (ret == 0)
ret = opt_remove_nops(env);
} else {
if (ret == 0)
sanitize_dead_code(env);
}
if (ret == 0)
/* program is valid, convert *(u32*)(ctx + off) accesses */
ret = convert_ctx_accesses(env);
if (ret == 0)
ret = fixup_bpf_calls(env);
if (ret == 0)
ret = fixup_call_args(env);
if (log->level && bpf_verifier_log_full(log))
ret = -ENOSPC;
if (log->level && !log->ubuf) {
ret = -EFAULT;
goto err_release_maps;
}
if (ret == 0 && env->used_map_cnt) {
/* if program passed verifier, update used_maps in bpf_prog_info */
env->prog->aux->used_maps = kmalloc_array(env->used_map_cnt,
sizeof(env->used_maps[0]),
GFP_KERNEL);
if (!env->prog->aux->used_maps) {
ret = -ENOMEM;
goto err_release_maps;
}
memcpy(env->prog->aux->used_maps, env->used_maps,
sizeof(env->used_maps[0]) * env->used_map_cnt);
env->prog->aux->used_map_cnt = env->used_map_cnt;
/* program is valid. Convert pseudo bpf_ld_imm64 into generic
* bpf_ld_imm64 instructions
*/
convert_pseudo_ld_imm64(env);
}
if (ret == 0)
adjust_btf_func(env);
err_release_maps:
if (!env->prog->aux->used_maps)
/* if we didn't copy map pointers into bpf_prog_info, release
* them now. Otherwise free_used_maps() will release them.
*/
release_maps(env);
*prog = env->prog;
err_unlock:
mutex_unlock(&bpf_verifier_lock);
vfree(env->insn_aux_data);
err_free_env:
kfree(env);
return ret;
}
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