From a55db635fd5b4ebe6ae012415db65426c2914b07 Mon Sep 17 00:00:00 2001 From: Michael Niedermayer Date: Sun, 22 Aug 2021 21:57:28 +0200 Subject: avcodec/mjpegbdec: Skip SOS on AVDISCARD_ALL as does mjpeg Fixes: NULL pointer dereference Fixes: 36342/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MJPEGB_fuzzer-4579188072906752 Fixes: 36344/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MJPEGB_fuzzer-5049579300061184 Fixes: 36345/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MJPEGB_fuzzer-5301149845553152 Fixes: 36374/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MJPEGB_fuzzer-6056312352931840 Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg Signed-off-by: Michael Niedermayer (cherry picked from commit 104a8399ae96f022a3662bd67668ad07e53e3093) Signed-off-by: Michael Niedermayer --- libavcodec/mjpegbdec.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/libavcodec/mjpegbdec.c b/libavcodec/mjpegbdec.c index 37d7bb8228..e09d1ea851 100644 --- a/libavcodec/mjpegbdec.c +++ b/libavcodec/mjpegbdec.c @@ -118,9 +118,13 @@ read_header: 8 * FFMIN(field_size, buf_end - buf_ptr - sos_offs)); s->mjpb_skiptosod = (sod_offs - sos_offs - show_bits(&s->gb, 16)); s->start_code = SOS; - ret = ff_mjpeg_decode_sos(s, NULL, 0, NULL); - if (ret < 0 && (avctx->err_recognition & AV_EF_EXPLODE)) - return ret; + if (avctx->skip_frame == AVDISCARD_ALL) { + skip_bits(&s->gb, get_bits_left(&s->gb)); + } else { + ret = ff_mjpeg_decode_sos(s, NULL, 0, NULL); + if (ret < 0 && (avctx->err_recognition & AV_EF_EXPLODE)) + return ret; + } } if (s->interlaced) { -- cgit v1.2.3