From c1c9a07eed04a744d8cd262af7c69f4832bfd0a5 Mon Sep 17 00:00:00 2001
From: Michael Niedermayer <michael@niedermayer.cc>
Date: Tue, 18 Jun 2024 15:48:23 +0200
Subject: [PATCH] avcodec/snowenc: MV limits due to mv_penalty table size
Fixes: out of array read
Fixes: 69673/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_SNOW_fuzzer-5476592894148608
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit 3a9292aff320d7b5048b371b1babea2f9b3c4e69)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
libavcodec/snowenc.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/libavcodec/snowenc.c b/libavcodec/snowenc.c
index e900c2b3fd..e053fa42dc 100644
--- a/libavcodec/snowenc.c
+++ b/libavcodec/snowenc.c
@@ -260,6 +260,7 @@ static int encode_q_branch(SnowContext *s, int level, int x, int y){
int my_context= av_log2(2*FFABS(left->my - top->my));
int s_context= 2*left->level + 2*top->level + tl->level + tr->level;
int ref, best_ref, ref_score, ref_mx, ref_my;
+ int range = MAX_MV >> (1 + qpel);
av_assert0(sizeof(s->block_state) >= 256);
if(s->keyframe){
@@ -301,6 +302,11 @@ static int encode_q_branch(SnowContext *s, int level, int x, int y){
c->xmax = - (x+1)*block_w + (w<<(LOG2_MB_SIZE - s->block_max_depth)) + 16-3;
c->ymax = - (y+1)*block_w + (h<<(LOG2_MB_SIZE - s->block_max_depth)) + 16-3;
+ c->xmin = FFMAX(c->xmin,-range);
+ c->xmax = FFMIN(c->xmax, range);
+ c->ymin = FFMAX(c->ymin,-range);
+ c->ymax = FFMIN(c->ymax, range);
+
if(P_LEFT[0] > (c->xmax<<shift)) P_LEFT[0] = (c->xmax<<shift);
if(P_LEFT[1] > (c->ymax<<shift)) P_LEFT[1] = (c->ymax<<shift);
if(P_TOP[0] > (c->xmax<<shift)) P_TOP[0] = (c->xmax<<shift);