[FFmpeg-devel] [PATCH] avcodec/sanm: Check w,h,left,top (PR #20268)

[FFmpeg-devel] [PATCH] avcodec/sanm: Check w,h,left,top (PR #20268)

[michaelni via ffmpeg-devel]

PR #20268 opened by michaelni
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20268
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20268.patch

The setup code fow w,h,left,top is complex, the code using it also falls in
at least 2 different classes, one using left/top the other not.

To ensure no out of array access happens we add this clear check.

Fixes: out of array access
Fixes: 439261995/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_SANM_fuzzer-5383455572819968

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>


From 134fbfd1dcb59441e38d870ddd231772f4e8e127 Mon Sep 17 00:00:00 2001
From: Michael Niedermayer <michael@niedermayer.cc>
Date: Sun, 17 Aug 2025 15:31:48 +0200
Subject: [PATCH] avcodec/sanm: Check w,h,left,top

The setup code fow w,h,left,top is complex, the code using it also falls in
at least 2 different classes, one using left/top the other not.

To ensure no out of array access happens we add this clear check.

Fixes: out of array access
Fixes: 439261995/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_SANM_fuzzer-5383455572819968

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
 libavcodec/sanm.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/libavcodec/sanm.c b/libavcodec/sanm.c
index a066a864eb..9e99aa9dd9 100644
--- a/libavcodec/sanm.c
+++ b/libavcodec/sanm.c
@@ -1757,6 +1757,11 @@ static int process_frame_obj(SANMVideoContext *ctx, GetByteContext *gb)
             memset(ctx->fbuf, 0, ctx->frm0_size);
     }
 
+    if (w + FFMAX(left, 0) > ctx->avctx->width || h + FFMAX(top, 0) > ctx->avctx->height) {
+        avpriv_request_sample(ctx->avctx, "overly large frame\n");
+        return AVERROR_PATCHWELCOME;
+    }
+
     switch (codec) {
     case 1:
     case 3:
-- 
2.49.1

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