From 051e0d7744dbb45f680bbfa72bfead947b11ef2f Mon Sep 17 00:00:00 2001 From: Michael Niedermayer Date: Wed, 16 Jul 2025 00:01:07 +0200 Subject: [PATCH] avcodec/ffv1dec: Check k in get_vlc_symbol() The true problem happens in several previous get_vlc_symbol() but checking that is more expensive (involving FFABS()) here its just a simple check between 2 variables we have. Fixes: Assertion log >= k failed at libavcodec/golomb.h:406 Fixes: 429296194/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_FFV1_DEC_fuzzer-4691594622337024 Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg Signed-off-by: Michael Niedermayer --- libavcodec/ffv1dec.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/libavcodec/ffv1dec.c b/libavcodec/ffv1dec.c index d613aa5395..d709e8ccbb 100644 --- a/libavcodec/ffv1dec.c +++ b/libavcodec/ffv1dec.c @@ -56,6 +56,11 @@ static inline int get_vlc_symbol(GetBitContext *gb, VlcState *const state, k++; i += i; } + if (k > bits) { + ff_dlog(NULL, "k-overflow bias:%d error:%d drift:%d count:%d k:%d", + state->bias, state->error_sum, state->drift, state->count, k); + k = bits; + } v = get_sr_golomb(gb, k, 12, bits); ff_dlog(NULL, "v:%d bias:%d error:%d drift:%d count:%d k:%d",