| Message ID | 20200618191909.2253-1-andreas.rheinhardt@gmail.com |
|---|---|
| State | Accepted |
| Commit | 6f06c17a55137855c67ba4a7b6778ca34ddbbe6b |
| Headers | show |
| Series | [FFmpeg-devel,v2,1/2] avcodec/cbs_av1: Fix writing uvlc numbers >= INT_MAX | expand |
| Context | Check | Description |
|---|---|---|
| andriy/default | pending | |
| andriy/make | success | Make finished |
| andriy/make_fate | success | Make fate finished |
diff --git a/libavcodec/cbs_av1.c b/libavcodec/cbs_av1.c index 29b316e011..0abcba9c60 100644 --- a/libavcodec/cbs_av1.c +++ b/libavcodec/cbs_av1.c @@ -125,8 +125,9 @@ static int cbs_av1_write_uvlc(CodedBitstreamContext *ctx, PutBitContext *pbc, put_bits(pbc, 1, 1); } else { zeroes = av_log2(value + 1); - v = value - (1 << zeroes) + 1; - put_bits(pbc, zeroes + 1, 1); + v = value - (1U << zeroes) + 1; + put_bits(pbc, zeroes, 0); + put_bits(pbc, 1, 1); put_bits(pbc, zeroes, v); }
Fixes: assertion failure Fixes: left shift of 1 by 31 places cannot be represented in type 'int' Fixes: 23264/clusterfuzz-testcase-minimized-ffmpeg_BSF_AV1_METADATA_fuzzer-6308429248593920 Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com> --- The earlier version did fix the undefined behaviour when shifting, but one nevertheless ran into an av_assert2 in put_bits because put_bits can't write 32 bits at once*. So write via three calls to put_bits. *: If one wants to write 32 bits at once and if there are 32 bits left (i.e. the cache is empty), then bit_buf will be shifted by 32 places which is undefined behaviour (even though bit_buf is zero in this case). libavcodec/cbs_av1.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)