Quoting Michael Niedermayer (2024-07-15 16:48:25)
> An alternative would be to leave the context unchanged on failure of
> hls_slice_header()
>
> Fixes: out of array access
> Fixes: NULL pointer dereference
> Fixes:
> 69584/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_HEVC_fuzzer-5931086299856896
> Fixes:
> 69724/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_HEVC_fuzzer-5104066422702080
>
> Found-by: continuous fuzzing process
> https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc>
> ---
> libavcodec/hevc/hevcdec.c | 12 ++++++++----
> 1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/libavcodec/hevc/hevcdec.c b/libavcodec/hevc/hevcdec.c
> index 0e4b26dad3b..80d59ab1916 100644
> --- a/libavcodec/hevc/hevcdec.c
> +++ b/libavcodec/hevc/hevcdec.c
> @@ -621,6 +621,10 @@ static int hls_slice_header(SliceHeader *sh, const
> HEVCContext *s, GetBitContext
>
> if (pps->dependent_slice_segments_enabled_flag)
> sh->dependent_slice_segment_flag = get_bits1(gb);
> + if (sh->dependent_slice_segment_flag && !s->slice_initialized) {
> + av_log(s->avctx, AV_LOG_ERROR, "dependent slice failed\n");
The new error message seems worse than the old one. A slice is a passive
object, "slice failed" makes no sense.
> @@ -3155,8 +3156,11 @@ static int decode_slice(HEVCContext *s, const H2645NAL
> *nal, GetBitContext *gb)
> int ret;
>
> ret = hls_slice_header(&s->sh, s, gb);
> - if (ret < 0)
> + if (ret < 0) {
> + //The code is not capable to rewind from an error, the state now is
> inconsistant so we cannot use it on depandant slices
^ ^
e e
Also I'd drop everything before the comma, why mention rewinding that is
not implemented and may not be a good idea anyway.
Otherwise patch LGTM.
--
Anton Khirnov
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