From 23127b33ec80e656921362d7dc82a0064bac20a2 Mon Sep 17 00:00:00 2001
From: Martin KaFai Lau <kafai@fb.com>
Date: Thu, 13 Dec 2018 10:41:46 -0800
Subject: [PATCH 1/2] bpf: Create a new btf_name_by_offset() for non type name
use case
The current btf_name_by_offset() is returning "(anon)" type name for
the offset == 0 case and "(invalid-name-offset)" for the out-of-bound
offset case.
It fits well for the internal BTF verbose log purpose which
is focusing on type. For example,
offset == 0 => "(anon)" => anonymous type/name.
Returning non-NULL for the bad offset case is needed
during the BTF verification process because the BTF verifier may
complain about another field first before discovering the name_off
is invalid.
However, it may not be ideal for the newer use case which does not
necessary mean type name. For example, when logging line_info
in the BPF verifier in the next patch, it is better to log an
empty src line instead of logging "(anon)".
The existing bpf_name_by_offset() is renamed to __bpf_name_by_offset()
and static to btf.c.
A new bpf_name_by_offset() is added for generic context usage. It
returns "\0" for name_off == 0 (note that btf->strings[0] is "\0")
and NULL for invalid offset. It allows the caller to decide
what is the best output in its context.
The new btf_name_by_offset() is overlapped with btf_name_offset_valid().
Hence, btf_name_offset_valid() is removed from btf.h to keep the btf.h API
minimal. The existing btf_name_offset_valid() usage in btf.c could also be
replaced later.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
include/linux/btf.h | 1 -
kernel/bpf/btf.c | 31 ++++++++++++++++++++-----------
kernel/bpf/verifier.c | 4 ++--
3 files changed, 22 insertions(+), 14 deletions(-)
diff --git a/include/linux/btf.h b/include/linux/btf.h
index a4cf075b89eb..58000d7e06e3 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -46,7 +46,6 @@ void btf_type_seq_show(const struct btf *btf, u32 type_id, void *obj,
struct seq_file *m);
int btf_get_fd_by_id(u32 id);
u32 btf_id(const struct btf *btf);
-bool btf_name_offset_valid(const struct btf *btf, u32 offset);
bool btf_type_is_reg_int(const struct btf_type *t, u32 expected_size);
#ifdef CONFIG_BPF_SYSCALL
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 1545ddfb6fa5..8fa0bf1c33fd 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -474,7 +474,7 @@ static bool btf_name_valid_identifier(const struct btf *btf, u32 offset)
return !*src;
}
-const char *btf_name_by_offset(const struct btf *btf, u32 offset)
+static const char *__btf_name_by_offset(const struct btf *btf, u32 offset)
{
if (!offset)
return "(anon)";
@@ -484,6 +484,14 @@ const char *btf_name_by_offset(const struct btf *btf, u32 offset)
return "(invalid-name-offset)";
}
+const char *btf_name_by_offset(const struct btf *btf, u32 offset)
+{
+ if (offset < btf->hdr.str_len)
+ return &btf->strings[offset];
+
+ return NULL;
+}
+
const struct btf_type *btf_type_by_id(const struct btf *btf, u32 type_id)
{
if (type_id > btf->nr_types)
@@ -576,7 +584,7 @@ __printf(4, 5) static void __btf_verifier_log_type(struct btf_verifier_env *env,
__btf_verifier_log(log, "[%u] %s %s%s",
env->log_type_id,
btf_kind_str[kind],
- btf_name_by_offset(btf, t->name_off),
+ __btf_name_by_offset(btf, t->name_off),
log_details ? " " : "");
if (log_details)
@@ -620,7 +628,7 @@ static void btf_verifier_log_member(struct btf_verifier_env *env,
btf_verifier_log_type(env, struct_type, NULL);
__btf_verifier_log(log, "\t%s type_id=%u bits_offset=%u",
- btf_name_by_offset(btf, member->name_off),
+ __btf_name_by_offset(btf, member->name_off),
member->type, member->offset);
if (fmt && *fmt) {
@@ -1872,7 +1880,7 @@ static s32 btf_enum_check_meta(struct btf_verifier_env *env,
btf_verifier_log(env, "\t%s val=%d\n",
- btf_name_by_offset(btf, enums[i].name_off),
+ __btf_name_by_offset(btf, enums[i].name_off),
enums[i].val);
}
@@ -1896,7 +1904,8 @@ static void btf_enum_seq_show(const struct btf *btf, const struct btf_type *t,
for (i = 0; i < nr_enums; i++) {
if (v == enums[i].val) {
seq_printf(m, "%s",
- btf_name_by_offset(btf, enums[i].name_off));
+ __btf_name_by_offset(btf,
+ enums[i].name_off));
return;
}
}
@@ -1954,20 +1963,20 @@ static void btf_func_proto_log(struct btf_verifier_env *env,
}
btf_verifier_log(env, "%u %s", args[0].type,
- btf_name_by_offset(env->btf,
- args[0].name_off));
+ __btf_name_by_offset(env->btf,
+ args[0].name_off));
for (i = 1; i < nr_args - 1; i++)
btf_verifier_log(env, ", %u %s", args[i].type,
- btf_name_by_offset(env->btf,
- args[i].name_off));
+ __btf_name_by_offset(env->btf,
+ args[i].name_off));
if (nr_args > 1) {
const struct btf_param *last_arg = &args[nr_args - 1];
if (last_arg->type)
btf_verifier_log(env, ", %u %s", last_arg->type,
- btf_name_by_offset(env->btf,
- last_arg->name_off));
+ __btf_name_by_offset(env->btf,
+ last_arg->name_off));
else
btf_verifier_log(env, ", vararg");
}
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 8b511a4fe84a..89ce2613fdb0 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4910,8 +4910,8 @@ static int check_btf_line(struct bpf_verifier_env *env,
goto err_free;
}
- if (!btf_name_offset_valid(btf, linfo[i].line_off) ||
- !btf_name_offset_valid(btf, linfo[i].file_name_off)) {
+ 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;
From d9762e84ede3eae9636f5dbbe0c8f0390d37e114 Mon Sep 17 00:00:00 2001
From: Martin KaFai Lau <kafai@fb.com>
Date: Thu, 13 Dec 2018 10:41:48 -0800
Subject: [PATCH 2/2] bpf: verbose log bpf_line_info in verifier
This patch adds bpf_line_info during the verifier's verbose.
It can give error context for debug purpose.
~~~~~~~~~~
Here is the verbose log for backedge:
while (a) {
a += bpf_get_smp_processor_id();
bpf_trace_printk(fmt, sizeof(fmt), a);
}
~> bpftool prog load ./test_loop.o /sys/fs/bpf/test_loop type tracepoint
13: while (a) {
3: a += bpf_get_smp_processor_id();
back-edge from insn 13 to 3
~~~~~~~~~~
Here is the verbose log for invalid pkt access:
Modification to test_xdp_noinline.c:
data = (void *)(long)xdp->data;
data_end = (void *)(long)xdp->data_end;
/*
if (data + 4 > data_end)
return XDP_DROP;
*/
*(u32 *)data = dst->dst;
~> bpftool prog load ./test_xdp_noinline.o /sys/fs/bpf/test_xdp_noinline type xdp
; data = (void *)(long)xdp->data;
224: (79) r2 = *(u64 *)(r10 -112)
225: (61) r2 = *(u32 *)(r2 +0)
; *(u32 *)data = dst->dst;
226: (63) *(u32 *)(r2 +0) = r1
invalid access to packet, off=0 size=4, R2(id=0,off=0,r=0)
R2 offset is outside of the packet
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
include/linux/bpf_verifier.h | 1 +
kernel/bpf/verifier.c | 74 +++++++++++++++++++++++++++++++++---
2 files changed, 70 insertions(+), 5 deletions(-)
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index c736945be7c5..548dcbdb7111 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -224,6 +224,7 @@ struct bpf_verifier_env {
bool allow_ptr_leaks;
bool seen_direct_write;
struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */
+ const struct bpf_line_info *prev_linfo;
struct bpf_verifier_log log;
struct bpf_subprog_info subprog_info[BPF_MAX_SUBPROGS + 1];
u32 subprog_cnt;
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 89ce2613fdb0..ba8e3134bbc2 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -26,6 +26,7 @@
#include <linux/bsearch.h>
#include <linux/sort.h>
#include <linux/perf_event.h>
+#include <linux/ctype.h>
#include "disasm.h"
@@ -216,6 +217,27 @@ struct bpf_call_arg_meta {
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)
{
@@ -266,6 +288,42 @@ __printf(2, 3) static void verbose(void *private_data, const char *fmt, ...)
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 ||
@@ -4561,6 +4619,7 @@ static int push_insn(int t, int w, int e, struct bpf_verifier_env *env)
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;
}
@@ -4578,6 +4637,8 @@ static int push_insn(int t, int w, int e, struct bpf_verifier_env *env)
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) {
@@ -4600,10 +4661,6 @@ static int check_cfg(struct bpf_verifier_env *env)
int ret = 0;
int i, t;
- ret = check_subprogs(env);
- if (ret < 0)
- return ret;
-
insn_state = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
if (!insn_state)
return -ENOMEM;
@@ -5448,6 +5505,8 @@ static int do_check(struct bpf_verifier_env *env)
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;
@@ -5521,6 +5580,7 @@ static int do_check(struct bpf_verifier_env *env)
.private_data = env,
};
+ verbose_linfo(env, insn_idx, "; ");
verbose(env, "%d: ", insn_idx);
print_bpf_insn(&cbs, insn, env->allow_ptr_leaks);
}
@@ -6755,7 +6815,7 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr,
env->allow_ptr_leaks = capable(CAP_SYS_ADMIN);
- ret = check_cfg(env);
+ ret = check_subprogs(env);
if (ret < 0)
goto skip_full_check;
@@ -6763,6 +6823,10 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr,
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);