strace/bpf_filter.c
Dmitry V. Levin d54388e1ce print_array: enhance printing of unfetchable object addresses
When umoven_func invocation fails to fetch data, it prints the faulty
address.  If this happens to a subsequent umoven_func invocation,
the printed address may be undistinguishable from a valid data printed
by print_func, e.g. when the data is printed in a numeric form like
[0x1, 0x2, 0x3, 0xdefaced].

Fix this source of confusion by moving the printing of the faulty
address from umoven_func to print_array itself.  This change renames
umoven_func to tfetch_mem_func and changes its semantics, so that
 - tfetch_mem_func never prints anything;
 - tfetch_mem_func returns true if the fetch succeeded,
   and false otherwise.

* defs.h (print_array): Replace umoven_func argument with
tfetch_mem_func.
* util.c (print_array): Replace umoven_func argument with
tfetch_mem_func, document expected tfetch_mem_func return value
semantics.  When tfetch_mem_func returns false, print either addr
or "... /* addr */" depending on the context (inside the array or not).
* bpf.c (print_ebpf_prog, print_bpf_prog_info,
BEGIN_BPF_CMD_DECODER(BPF_PROG_QUERY)): Replace umoven_or_printaddr
argument of print_array with tfetch_mem.
* bpf_filter.c (print_bpf_fprog): Likewise.
* btrfs.c (btrfs_print_logical_ino_container,
btrfs_print_ino_path_container, btrfs_print_qgroup_inherit,
btrfs_ioctl): Likewise.
* dm.c (dm_decode_dm_target_deps): Likewise.
* epoll.c (epoll_wait_common): Likewise.
* file_ioctl.c (file_ioctl): Likewise.
* ipc_sem.c (tprint_sembuf_array): Likewise.
* kexec.c (print_kexec_segments): Likewise.
* mem.c (SYS_FUNC(subpage_prot)): Likewise.
* net.c (print_getsockopt): Likewise.
* netlink.c (decode_nlmsgerr_attr_cookie): Likewise.
* netlink_netlink_diag.c (decode_netlink_diag_groups): Likewise.
* netlink_packet_diag.c (decode_packet_diag_mclist): Likewise.
* netlink_unix_diag.c (decode_unix_diag_inode): Likewise.
* nlattr.c (decode_nla_meminfo): Likewise.
* numa.c (print_nodemask, SYS_FUNC(move_pages),
* perf_ioctl.c (perf_ioctl_query_bpf): Likewise.
* poll.c (decode_poll_entering): Likewise.
* printsiginfo.c (print_siginfo_array): Likewise.
* rtnl_tc.c (decode_tca_stab_data): Likewise.
* sock.c (decode_ifconf): Likewise.
* uid.c (print_groups): Likewise.
* io.c (SYS_FUNC(io_submit), SYS_FUNC(io_getevents)): Replace
umoven_or_printaddr argument of print_array with tfetch_mem.
(tprint_iov_upto): Replace umoven_or_printaddr_ignore_syserror
with tfetch_mem_ignore_syserror.
* v4l2.c (print_v4l2_format_fmt): Replace umoven_or_printaddr argument
of print_array with tfetch_mem.
(print_v4l2_ext_controls): Replace umoven_or_printaddr_ignore_syserror
with tfetch_mem_ignore_syserror.
* mmsghdr.c (fetch_struct_mmsghdr_or_printaddr): Rename
to fetch_struct_mmsghdr_for_print, do not print address, return bool.
(decode_mmsgvec): Replace fetch_struct_mmsghdr_or_printaddr
with fetch_struct_mmsghdr_for_print.
* tests/aio.c (main): Update expected output.
* tests/bpf.c (print_BPF_PROG_QUERY_attr5): Likewise.
* tests/ioctl_perf-success.c (main): Likewise.
* tests/ioctl_v4l2.c (main): Update expected output.
* tests/kexec_load.c (main): Likewise.
* tests/mmsg_name.c (test_mmsg_name): Update expected output.
* tests/move_pages.c (print_page_array, print_node_array): Likewise.
* tests/poll.c (print_pollfd_array_entering): Likewise.
* tests/preadv-pwritev.c (main): Likewise.
* tests/preadv2-pwritev2.c (dumpio): Likewise.
* tests/process_vm_readv_writev.c (print_iov): Likewise.
* tests/pwritev.c (print_iovec): Likewise.
* tests/readv.c (main): Likewise.
* tests/seccomp-filter-v.c
* tests/semop.c (main): Likewise.
* tests/set_mempolicy.c (print_nodes): Likewise.
* tests/setgroups.c (main): Likewise.
* tests/test_nlattr.h (print_nlattr) Likewise.

Co-Authored-by: Eugene Syromyatnikov <evgsyr@gmail.com>
2018-05-29 09:58:10 +00:00

202 lines
5.3 KiB
C

/*
* Decoder of classic BPF programs.
*
* Copyright (c) 2015-2017 Dmitry V. Levin <ldv@altlinux.org>
* Copyright (c) 2017-2018 The strace developers.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "defs.h"
#include "bpf_filter.h"
#include "bpf_fprog.h"
#include <linux/filter.h>
#include "xlat/bpf_class.h"
#include "xlat/bpf_miscop.h"
#include "xlat/bpf_mode.h"
#include "xlat/bpf_op_alu.h"
#include "xlat/bpf_op_jmp.h"
#include "xlat/bpf_rval.h"
#include "xlat/bpf_size.h"
#include "xlat/bpf_src.h"
#include "xlat/ebpf_class.h"
#include "xlat/ebpf_mode.h"
#include "xlat/ebpf_op_alu.h"
#include "xlat/ebpf_op_jmp.h"
#include "xlat/ebpf_size.h"
void
print_bpf_filter_code(const uint16_t code, bool extended)
{
const struct xlat *mode = extended ? ebpf_mode : bpf_mode;
uint16_t i = code & ~BPF_CLASS(code);
if (extended)
printxval_index(ebpf_class, BPF_CLASS(code), "BPF_???");
else
printxval_index(bpf_class, BPF_CLASS(code), "BPF_???");
switch (BPF_CLASS(code)) {
case BPF_ST:
case BPF_STX:
if (!extended) {
if (i) {
tprintf("|%#x", i);
tprints_comment("BPF_???");
}
break;
}
ATTRIBUTE_FALLTHROUGH; /* extended == true */
case BPF_LD:
case BPF_LDX:
tprints("|");
printxvals(BPF_SIZE(code), "BPF_???",
bpf_size, extended ? ebpf_size : NULL, NULL);
tprints("|");
printxval(mode, BPF_MODE(code), "BPF_???");
break;
case BPF_MISC: /* BPF_ALU64 in eBPF */
if (!extended) {
tprints("|");
printxval(bpf_miscop, BPF_MISCOP(code), "BPF_???");
i &= ~BPF_MISCOP(code);
if (i) {
tprintf("|%#x", i);
tprints_comment("BPF_???");
}
break;
}
ATTRIBUTE_FALLTHROUGH; /* extended == true */
case BPF_ALU:
tprints("|");
printxval(bpf_src, BPF_SRC(code), "BPF_???");
tprints("|");
printxvals(BPF_OP(code), "BPF_???",
bpf_op_alu,
extended ? ebpf_op_alu : NULL, NULL);
break;
case BPF_JMP:
tprints("|");
printxval(bpf_src, BPF_SRC(code), "BPF_???");
tprints("|");
printxvals(BPF_OP(code), "BPF_???",
bpf_op_jmp, extended ? ebpf_op_jmp : NULL, NULL);
break;
case BPF_RET: /* Reserved in eBPF */
if (!extended) {
tprints("|");
printxval(bpf_rval, BPF_RVAL(code), "BPF_???");
i &= ~BPF_RVAL(code);
}
if (i) {
tprintf("|%#x", i);
tprints_comment("BPF_???");
}
break;
}
}
static void
print_bpf_filter_stmt(const struct bpf_filter_block *const filter,
const print_bpf_filter_fn print_k)
{
tprints("BPF_STMT(");
print_bpf_filter_code(filter->code, false);
tprints(", ");
if (!print_k || !print_k(filter))
tprintf("%#x", filter->k);
tprints(")");
}
static void
print_bpf_filter_jump(const struct bpf_filter_block *const filter)
{
tprints("BPF_JUMP(");
print_bpf_filter_code(filter->code, false);
tprintf(", %#x, %#x, %#x)", filter->k, filter->jt, filter->jf);
}
struct bpf_filter_block_data {
const print_bpf_filter_fn fn;
unsigned int count;
};
static bool
print_bpf_filter_block(struct tcb *const tcp, void *const elem_buf,
const size_t elem_size, void *const data)
{
const struct bpf_filter_block *const filter = elem_buf;
struct bpf_filter_block_data *const fbd = data;
if (fbd->count++ >= BPF_MAXINSNS) {
tprints("...");
return false;
}
if (filter->jt || filter->jf)
print_bpf_filter_jump(filter);
else
print_bpf_filter_stmt(filter, fbd->fn);
return true;
}
void
print_bpf_fprog(struct tcb *const tcp, const kernel_ulong_t addr,
const unsigned short len, const print_bpf_filter_fn print_k)
{
if (abbrev(tcp)) {
printaddr(addr);
} else {
struct bpf_filter_block_data fbd = { .fn = print_k };
struct bpf_filter_block filter;
print_array(tcp, addr, len, &filter, sizeof(filter),
tfetch_mem, print_bpf_filter_block, &fbd);
}
}
void
decode_bpf_fprog(struct tcb *const tcp, const kernel_ulong_t addr,
const print_bpf_filter_fn print_k)
{
struct bpf_fprog fprog;
if (fetch_bpf_fprog(tcp, addr, &fprog)) {
tprintf("{len=%hu, filter=", fprog.len);
print_bpf_fprog(tcp, fprog.filter, fprog.len, print_k);
tprints("}");
}
}