[FFmpeg-devel] [PATCH 1/2] avcodec/snowdec: Check intra block dc differences.

[Michael Niedermayer]

Fixes: Timeout
Fixes: 3142/clusterfuzz-testcase-5007853163118592

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
---
 libavcodec/snowdec.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/libavcodec/snowdec.c b/libavcodec/snowdec.c
index 727e908fb5..77ffe7f594 100644
--- a/libavcodec/snowdec.c
+++ b/libavcodec/snowdec.c
@@ -183,13 +183,24 @@ static int decode_q_branch(SnowContext *s, int level, int x, int y){
         int my_context= av_log2(2*FFABS(left->my - top->my)) + 0*av_log2(2*FFABS(tr->my - top->my));
 
         type= get_rac(&s->c, &s->block_state[1 + left->type + top->type]) ? BLOCK_INTRA : 0;
-
         if(type){
+            int ld, cbd, crd;
             pred_mv(s, &mx, &my, 0, left, top, tr);
-            l += get_symbol(&s->c, &s->block_state[32], 1);
+            ld = get_symbol(&s->c, &s->block_state[32], 1);
+            if (ld < -255 || ld > 255) {
+                av_log(s->avctx, AV_LOG_DEBUG, "Invalid (Out of range) intra luma block DC difference %d\n", ld);
+                return AVERROR_INVALIDDATA;
+            }
+            l += ld;
             if (s->nb_planes > 2) {
-                cb+= get_symbol(&s->c, &s->block_state[64], 1);
-                cr+= get_symbol(&s->c, &s->block_state[96], 1);
+                cbd = get_symbol(&s->c, &s->block_state[64], 1);
+                crd = get_symbol(&s->c, &s->block_state[96], 1);
+                if (cbd < -255 || cbd > 255 || crd < -255 || crd > 255) {
+                    av_log(s->avctx, AV_LOG_DEBUG, "Invalid (Out of range) intra chroma block DC difference %d, %d\n", cbd, crd);
+                    return AVERROR_INVALIDDATA;
+                }
+                cb += cbd;
+                cr += crd;
             }
         }else{
             if(s->ref_frames > 1)
-- 
2.15.0