[FFmpeg-devel] [PATCH] Fix flacdec int overflow with a saturated add (PR #20900)

[usepgp via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

PR #20900 opened by usepgp
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20900
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20900.patch

A chromium fuzzer identified this potential UB int overflow.


>From d55c6e8a2c49319eb779ec795fdd657cbc524fc7 Mon Sep 17 00:00:00 2001
From: Ted Meyer <tmathmeyer@chromium.org>
Date: Wed, 15 Oct 2025 14:00:18 -0700
Subject: [PATCH] Fix flacdec int overflow with a saturated add

A chromium fuzzer identified this.
---
 libavformat/flacdec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavformat/flacdec.c b/libavformat/flacdec.c
index e80b49307d..219bc4e416 100644
--- a/libavformat/flacdec.c
+++ b/libavformat/flacdec.c
@@ -47,7 +47,7 @@ static void reset_index_position(int64_t metadata_head_size, AVStream *st)
     FFStream *const sti = ffstream(st);
     /* the real seek index offset should be the size of metadata blocks with the offset in the frame blocks */
     for (int i = 0; i < sti->nb_index_entries; i++)
-        sti->index_entries[i].pos += metadata_head_size;
+        sti->index_entries[i].pos = av_sat_add64(sti->index_entries[i].pos, metadata_head_size);
 }
 
 static const uint16_t sr_table[16] = {
-- 
2.49.1

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