On 12/8/2019 6:31 PM, Michael Niedermayer wrote: > This allows writing empty slices
Are empty slices valid in mpeg2 to begin with? Or is that the result of invalid/truncated data exclusively? The code in cbs_mpeg2_write_slice() is run only when slice->data is not NULL, which after a cursory look at cbs_mpeg2_read_slice() it looks like is always the case (It will always have a pointer, even if it points to the very end of the buffer). In contrast, slice->data_size can be zero, so maybe the check here should be slice->data_size != 0 instead, which should fix this assertion failure without changing the it or what data the module will accept. > > Fixes: Assertion slice->data_bit_start >= 0 && slice->data_size > > slice->data_bit_start / 8 failed at libavcodec/cbs_mpeg2.c:340 > Fixes: > 19280/clusterfuzz-testcase-minimized-ffmpeg_BSF_MPEG2_METADATA_fuzzer-5632206173372416 > > Found-by: continuous fuzzing process > https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg > Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc> > --- > libavcodec/cbs_mpeg2.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/libavcodec/cbs_mpeg2.c b/libavcodec/cbs_mpeg2.c > index 13d871cc89..b5286537db 100644 > --- a/libavcodec/cbs_mpeg2.c > +++ b/libavcodec/cbs_mpeg2.c > @@ -337,7 +337,7 @@ static int cbs_mpeg2_write_slice(CodedBitstreamContext > *ctx, > uint8_t *pos = slice->data + slice->data_bit_start / 8; > > av_assert0(slice->data_bit_start >= 0 && > - slice->data_size > slice->data_bit_start / 8); > + slice->data_size * 8LL >= slice->data_bit_start); > > if (slice->data_size * 8 + 8 > put_bits_left(pbc)) > return AVERROR(ENOSPC); > _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
