[FFmpeg-devel] [FFmpeg-cvslog] avcodec/mpeg_er: Don't set block_index unnecessarily
Michael Niedermayer
michael at niedermayer.cc
Wed Oct 9 23:16:15 EEST 2024
On Mon, Jul 01, 2024 at 02:36:23PM +0200, Andreas Rheinhardt wrote:
> Michael Niedermayer:
> > On Thu, Jun 20, 2024 at 05:01:08PM +0000, Andreas Rheinhardt wrote:
> >> ffmpeg | branch: master | Andreas Rheinhardt <andreas.rheinhardt at 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.rheinhardt at 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
> >
>
> Sorry for this. I knew that VC-1 (and RV34) use ff_mpv_reconstruct_mb()
> for error resilience, but I thought that everything would be fine given
> that they initialize block_index. Apparently I was wrong. Anyway, I have
> sent a patch that should fix this:
> https://ffmpeg.org/pipermail/ffmpeg-devel/2024-July/330463.html Please
> confirm that it indeed does fix it.
>
> - Andreas
>
> PS: This patchset also includes a patch that effectively reverts a patch
> of yours:
> https://ffmpeg.org/pipermail/ffmpeg-devel/2024-July/330471.html Can you
> test that it does not reenable the bug your patch fixed?
ive approved that patch 2 weeks ago, is there something else you want me to do ?
thx
[...]
--
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
I do not agree with what you have to say, but I'll defend to the death your
right to say it. -- Voltaire
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