On Wed, Oct 13, 2021 at 06:15:26PM +0200, Mattias Wadman wrote: > Reduces the risk of finding false frames that happens to have valid values > and CRC. > > Fixes ticket #9185 ffmpeg flac decoder incorrectly finds junk frame > https://trac.ffmpeg.org/ticket/9185 > --- > libavcodec/flac_parser.c | 30 ++++++++++++++++++++++++++++-- > 1 file changed, 28 insertions(+), 2 deletions(-)
After this was applied out of array accesses appeared
tools/target_dem_flac_fuzzer: Running 1 inputs 1 time(s) each.
Running:
libfuzz-repro/40109/clusterfuzz-testcase-minimized-ffmpeg_dem_FLAC_fuzzer-4805686811295744
=================================================================
==30399==ERROR: AddressSanitizer: heap-buffer-overflow on address
0x633000052800 at pc 0x000001734048 bp 0x7ffd3598d090 sp 0x7ffd3598d088
READ of size 4 at 0x633000052800 thread T0
#0 0x1734047 in get_bits libavcodec/get_bits.h:404:5
#1 0x1734047 in frame_header_is_valid libavcodec/flac_parser.c:118
#2 0x173ac77 in find_headers_search_validate libavcodec/flac_parser.c:202:9
#3 0x173a851 in find_headers_search libavcodec/flac_parser.c:248:31
#4 0x172f29b in find_new_headers libavcodec/flac_parser.c:268:18
#5 0x172f29b in flac_parse libavcodec/flac_parser.c:666
#6 0x13fb138 in av_parser_parse2 libavcodec/parser.c:165:13
#7 0x6f1dba in parse_packet libavformat/demux.c:1127:15
#8 0x6befe7 in read_frame_internal libavformat/demux.c:1322:24
#9 0x6bafca in av_read_frame libavformat/demux.c:1426:17
#10 0x4c7832 in LLVMFuzzerTestOneInput tools/target_dem_fuzzer.c:197:15
#11 0x27055bd in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*,
unsigned long) Fuzzer/build/../FuzzerLoop.cpp:495:13
#12 0x26fa192 in fuzzer::RunOneTest(fuzzer::Fuzzer*, char const*, unsigned
long) Fuzzer/build/../FuzzerDriver.cpp:273:6
#13 0x26ff391 in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char
const*, unsigned long)) Fuzzer/build/../FuzzerDriver.cpp:690:9
#14 0x26f9e70 in main Fuzzer/build/../FuzzerMain.cpp:20:10
#15 0x7f5d338b8bf6 in __libc_start_main
/build/glibc-S9d2JN/glibc-2.27/csu/../csu/libc-start.c:310
#16 0x41fb79 in _start (tools/target_dem_flac_fuzzer+0x41fb79)
0x633000052800 is located 0 bytes to the right of 106496-byte region
[0x633000038800,0x633000052800)
allocated by thread T0 here:
#0 0x498597 in posix_memalign
/b/swarming/w/ir/cache/builder/src/third_party/llvm/compiler-rt/lib/asan/asan_malloc_linux.cc:226:3
#1 0x26112c8 in av_malloc libavutil/mem.c:104:9
#2 0x25a67b3 in av_fifo_alloc_array libavutil/fifo.c:51:20
#3 0x172c9b6 in flac_parse_init libavcodec/flac_parser.c:747:21
#4 0x13f7d67 in av_parser_init libavcodec/parser.c:67:15
#5 0x6ce0b8 in avformat_find_stream_info libavformat/demux.c:2453:27
#6 0x4c77d0 in LLVMFuzzerTestOneInput tools/target_dem_fuzzer.c:192:11
#7 0x27055bd in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*,
unsigned long) Fuzzer/build/../FuzzerLoop.cpp:495:13
#8 0x26fa192 in fuzzer::RunOneTest(fuzzer::Fuzzer*, char const*, unsigned
long) Fuzzer/build/../FuzzerDriver.cpp:273:6
#9 0x26ff391 in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char
const*, unsigned long)) Fuzzer/build/../FuzzerDriver.cpp:690:9
#10 0x26f9e70 in main Fuzzer/build/../FuzzerMain.cpp:20:10
#11 0x7f5d338b8bf6 in __libc_start_main
/build/glibc-S9d2JN/glibc-2.27/csu/../csu/libc-start.c:310
SUMMARY: AddressSanitizer: heap-buffer-overflow libavcodec/get_bits.h:404:5 in
get_bits
Shadow bytes around the buggy address:
0x0c66800024b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c66800024c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c66800024d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c66800024e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c66800024f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c6680002500:[fa]fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c6680002510: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c6680002520: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c6680002530: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c6680002540: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c6680002550: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
Addressable: 00
Partially addressable: 01 02 03 04 05 06 07
Heap left redzone: fa
Freed heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
Stack after return: f5
Stack use after scope: f8
Global redzone: f9
Global init order: f6
Poisoned by user: f7
Container overflow: fc
Array cookie: ac
Intra object redzone: bb
ASan internal: fe
Left alloca redzone: ca
Right alloca redzone: cb
Shadow gap: cc
==30399==ABORTING
[...]
--
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
The misfortune of the wise is better than the prosperity of the fool.
-- Epicurus
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