On Thu, Jun 20, 2024 at 05:01:08PM +0000, Andreas Rheinhardt wrote: > ffmpeg | branch: master | Andreas Rheinhardt <andreas.rheinha...@outlook.com> > | Wed Jun 12 08:37:53 2024 +0200| [65d5ccb808ec93de46a2458ea8cc082ce4460f34] > | committer: Andreas Rheinhardt > > avcodec/mpeg_er: Don't set block_index unnecessarily > > ff_init_block_index() sets MpegEncContext.dest and > MpegEncContext.block_index. The latter is unused by > ff_mpv_reconstruct_mb() (which is what this code is > preparatory for) and dest is overwritten a few lines below. > So don't initialize block_index at all. > > Signed-off-by: Andreas Rheinhardt <andreas.rheinha...@outlook.com> > > > http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=65d5ccb808ec93de46a2458ea8cc082ce4460f34 > --- > > libavcodec/mpeg_er.c | 4 ---- > 1 file changed, 4 deletions(-) > > diff --git a/libavcodec/mpeg_er.c b/libavcodec/mpeg_er.c > index e7b3197bb1..fe7dcd7efb 100644 > --- a/libavcodec/mpeg_er.c > +++ b/libavcodec/mpeg_er.c > @@ -76,10 +76,6 @@ static void mpeg_er_decode_mb(void *opaque, int ref, int > mv_dir, int mv_type, > s->mcsel = 0; > memcpy(s->mv, mv, sizeof(*mv)); > > - ff_init_block_index(s); > - ff_update_block_index(s, s->avctx->bits_per_raw_sample, > - s->avctx->lowres, s->chroma_x_shift); > - > s->bdsp.clear_blocks(s->block[0]); > if (!s->chroma_y_shift) > s->bdsp.clear_blocks(s->block[6]);
It seems not unnneccesary
Running:
69814/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_VC1_fuzzer-4868081575329792
=================================================================
==2146502==ERROR: AddressSanitizer: heap-buffer-overflow on address
0x625000009c80 at pc 0x00000049b63f bp 0x7ffdecbf28c0 sp 0x7ffdecbf2088
WRITE of size 64 at 0x625000009c80 thread T0
#0 0x49b63e in __asan_memset
/b/swarming/w/ir/cache/builder/src/third_party/llvm/compiler-rt/lib/asan/asan_interceptors_memintrinsics.cc:26:3
#1 0xe85598 in ff_clean_intra_table_entries
ffmpeg/libavcodec/mpegvideo.c:809:5
#2 0xe9b926 in mpv_reconstruct_mb_internal
ffmpeg/libavcodec/mpv_reconstruct_mb_template.c:68:17
#3 0xe9b926 in ff_mpv_reconstruct_mb ffmpeg/libavcodec/mpegvideo_dec.c:935
#4 0xb1f790 in guess_mv ffmpeg/libavcodec/error_resilience.c:456:17
#5 0xb0f9b5 in ff_er_frame_end ffmpeg/libavcodec/error_resilience.c:1224:9
#6 0x63e595 in vc1_decode_frame ffmpeg/libavcodec/vc1dec.c:1341:13
#7 0x4fe53f in decode_simple_internal ffmpeg/libavcodec/decode.c:429:20
#8 0x4fe53f in decode_simple_receive_frame ffmpeg/libavcodec/decode.c:600
#9 0x4fe53f in decode_receive_frame_internal ffmpeg/libavcodec/decode.c:631
#10 0x4fcf6d in avcodec_send_packet ffmpeg/libavcodec/decode.c:721:15
#11 0x4d1da7 in LLVMFuzzerTestOneInput
ffmpeg/tools/target_dec_fuzzer.c:533:25
#12 0x166259d in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*,
unsigned long) Fuzzer/build/../FuzzerLoop.cpp:495:13
#13 0x1657172 in fuzzer::RunOneTest(fuzzer::Fuzzer*, char const*, unsigned
long) Fuzzer/build/../FuzzerDriver.cpp:273:6
#14 0x165c371 in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char
const*, unsigned long)) Fuzzer/build/../FuzzerDriver.cpp:690:9
#15 0x1656e50 in main Fuzzer/build/../FuzzerMain.cpp:20:10
#16 0x7fd643b76082 in __libc_start_main
(/lib/x86_64-linux-gnu/libc.so.6+0x24082)
#17 0x423f6d in _start (ffmpeg/tools/target_dec_vc1_fuzzer+0x423f6d)
Address 0x625000009c80 is a wild pointer.
SUMMARY: AddressSanitizer: heap-buffer-overflow
/b/swarming/w/ir/cache/builder/src/third_party/llvm/compiler-rt/lib/asan/asan_interceptors_memintrinsics.cc:26:3
in __asan_memset
Shadow bytes around the buggy address:
0x0c4a7fff9340: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c4a7fff9350: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c4a7fff9360: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c4a7fff9370: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c4a7fff9380: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
=>0x0c4a7fff9390:[fa]fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c4a7fff93a0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c4a7fff93b0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c4a7fff93c0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c4a7fff93d0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c4a7fff93e0: 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
==2146502==ABORTING
[...]
--
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
Avoid a single point of failure, be that a person or equipment.
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