PR #22839 opened by Kacper Michajłow (kasper93)
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/22839
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/22839.patch

When use_loop == true and idx < 0, we would incorrectly check
in_stride[idx], which is OOB read. Check !use_loop first, as we know by
the condition above that idx >= 0 has to be true in this case.


From 3ada2b6c8a27ffbebe3998c41ee0eebae92e2870 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Kacper=20Michaj=C5=82ow?= <[email protected]>
Date: Thu, 16 Apr 2026 19:42:19 +0200
Subject: [PATCH] swscale/ops_memcpy: guard exec->in_stride[-1] access
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

When use_loop == true and idx < 0, we would incorrectly check
in_stride[idx], which is OOB read. Check !use_loop first, as we know by
the condition above that idx >= 0 has to be true in this case.

Signed-off-by: Kacper Michajłow <[email protected]>
---
 libswscale/ops_memcpy.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libswscale/ops_memcpy.c b/libswscale/ops_memcpy.c
index 4d0477b754..d168e3135e 100644
--- a/libswscale/ops_memcpy.c
+++ b/libswscale/ops_memcpy.c
@@ -51,7 +51,7 @@ static void process(const SwsOpExec *exec, const void *priv,
         const int use_loop = exec->out_stride[i] > bytes + SWS_MAX_PADDING;
         if (idx < 0 && !use_loop) {
             memset(out, p->clear_value[i], exec->out_stride[i] * lines);
-        } else if (exec->out_stride[i] == exec->in_stride[idx] && !use_loop) {
+        } else if (!use_loop && exec->out_stride[i] == exec->in_stride[idx]) {
             memcpy(out, exec->in[idx], exec->out_stride[i] * lines);
         } else if (idx < 0) {
             for (int y = y_start; y < y_end; y++) {
-- 
2.52.0

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