Change #266515

Comments

avcodec/hevc: limit missing-ref fill to coded planes
generate_missing_ref walked frame->f->data[] until a NULL slot, which
on alpha-video frames extended to data[3] and read
sps->hshift[3]/vshift[3] out of bounds.

The alpha plane is produced by the alpha layer via
replace_alpha_plane; the base decoder path never reads or writes it.
Bound the fill loop by the SPS coded plane count. This both removes
the out-of-bounds shift access and avoids an unnecessary full-frame
memset of the alpha plane.

Fixes: out of array read
Fixes: 500770604/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_HEVC_fuzzer-6157374833623040

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg

Changed files

• libavcodec/hevc/refs.c