Commit c61944093f for ffmpeg

commit c61944093f57dccb9079bad1612418b2ccb3f6c1
Author: Michael Niedermayer <michael@niedermayer.cc>
Date:   Sun Oct 11 07:31:13 2026 +0200

    swscale: reject interlaced frames whose fields have no lines

    A one line interlaced frame has an empty bottom field, when source and
    destination format were equal the graph was still built for it and
    divided by the zero slice height.

    Fixes: division by zero
    Fixes: 9FwqJRpgNJo3
    Found during the review of https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/24851
    Division by zero Replicated through UnModified FFmpeg with UBSAN

diff --git a/libswscale/swscale.c b/libswscale/swscale.c
index d224c3275b..070b0f5939 100644
--- a/libswscale/swscale.c
+++ b/libswscale/swscale.c
@@ -1562,6 +1562,12 @@ int sws_frame_setup(SwsContext *ctx, const AVFrame *dst, const AVFrame *src)
             goto fail;
         }

+        if (src_fmt.height <= 0 || dst_fmt.height <= 0) {
+            err_msg = "Interlaced frames need at least two lines";
+            ret = AVERROR(EINVAL);
+            goto fail;
+        }
+
         src_ok = ff_test_fmt(backends, &src_fmt, 0);
         dst_ok = ff_test_fmt(backends, &dst_fmt, 1);
         if ((!src_ok || !dst_ok) && !ff_fmt_equal(&src_fmt, &dst_fmt)) {