From b66384b77fb596e7b110cf7b493fffd6c45a9d85 Mon Sep 17 00:00:00 2001 From: Michael Niedermayer Date: Tue, 31 Aug 2021 20:15:09 +0200 Subject: [PATCH] avcodec/mpeg12dec: Do not put mpeg_f_code into an invalid state on error return Fixes: invalid shift Fixes: 37018/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MPEG2VIDEO_fuzzer-5290280902328320 Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg Signed-off-by: Michael Niedermayer (cherry picked from commit 5a95abcce4d93f979e4b53f2220f7a54edd03312) Signed-off-by: Michael Niedermayer --- libavcodec/mpeg12dec.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/libavcodec/mpeg12dec.c b/libavcodec/mpeg12dec.c index 99e56532a5..85e755d5dd 100644 --- a/libavcodec/mpeg12dec.c +++ b/libavcodec/mpeg12dec.c @@ -1545,6 +1545,10 @@ static void mpeg_decode_picture_coding_extension(Mpeg1Context *s1) s->mpeg_f_code[0][1] = get_bits(&s->gb, 4); s->mpeg_f_code[1][0] = get_bits(&s->gb, 4); s->mpeg_f_code[1][1] = get_bits(&s->gb, 4); + s->mpeg_f_code[0][0] += !s->mpeg_f_code[0][0]; + s->mpeg_f_code[0][1] += !s->mpeg_f_code[0][1]; + s->mpeg_f_code[1][0] += !s->mpeg_f_code[1][0]; + s->mpeg_f_code[1][1] += !s->mpeg_f_code[1][1]; if (!s->pict_type && s1->mpeg_enc_ctx_allocated) { av_log(s->avctx, AV_LOG_ERROR, "Missing picture start code, guessing missing values\n"); @@ -1558,10 +1562,6 @@ static void mpeg_decode_picture_coding_extension(Mpeg1Context *s1) s->current_picture.f->pict_type = s->pict_type; s->current_picture.f->key_frame = s->pict_type == AV_PICTURE_TYPE_I; } - s->mpeg_f_code[0][0] += !s->mpeg_f_code[0][0]; - s->mpeg_f_code[0][1] += !s->mpeg_f_code[0][1]; - s->mpeg_f_code[1][0] += !s->mpeg_f_code[1][0]; - s->mpeg_f_code[1][1] += !s->mpeg_f_code[1][1]; s->intra_dc_precision = get_bits(&s->gb, 2); s->picture_structure = get_bits(&s->gb, 2);