PR #21273 opened by michaelni
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21273
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21273.patch

Fixes: shift exponent -1 is negative
Fixes: 
429330004/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_JPEG2000_DEC_fuzzer-4733213845291008

Found-by:  continuous fuzzing process 
https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <[email protected]>


>From 4b7bf41ff0d77bccad4ffea7f4dfbc438bcfbc14 Mon Sep 17 00:00:00 2001
From: Michael Niedermayer <[email protected]>
Date: Mon, 22 Dec 2025 23:17:24 +0100
Subject: [PATCH] avcodec/jpeg2000dec: Make M_b check broader

Fixes: shift exponent -1 is negative
Fixes: 
429330004/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_JPEG2000_DEC_fuzzer-4733213845291008

Found-by:  continuous fuzzing process 
https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <[email protected]>
---
 libavcodec/jpeg2000dec.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/libavcodec/jpeg2000dec.c b/libavcodec/jpeg2000dec.c
index de1a73b92b..276c0a6e43 100644
--- a/libavcodec/jpeg2000dec.c
+++ b/libavcodec/jpeg2000dec.c
@@ -2270,8 +2270,8 @@ static inline int tile_codeblocks(const 
Jpeg2000DecoderContext *s, Jpeg2000Tile
                     band->coord[1][0] == band->coord[1][1])
                     continue;
 
-                if ((codsty->cblk_style & JPEG2000_CTSY_HTJ2K_F) && M_b >= 31) 
{
-                    avpriv_request_sample(s->avctx, "JPEG2000_CTSY_HTJ2K_F and 
M_b >= 31");
+                if (M_b >= 31) {
+                    avpriv_request_sample(s->avctx, "M_b >= 31");
                     return AVERROR_PATCHWELCOME;
                 }
 
-- 
2.49.1

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