[FFmpeg-devel] [PATCH] avfilter/vf_thumbnail: fix buffer overflow for odd sized HBD inputs (PR #20132)

[Niklas Haas]

PR #20132 opened by Niklas Haas (haasn)
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20132
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20132.patch

This histogram index was not correctly downshifted to 8-bit.


From 651ce7dbc9cb88ab01002867ddb5b44a6f17a647 Mon Sep 17 00:00:00 2001
From: Niklas Haas <git at haasn.dev>
Date: Wed, 6 Aug 2025 12:11:59 +0200
Subject: [PATCH] avfilter/vf_thumbnail: fix buffer overflow for odd sized HBD
 inputs

This histogram index was not correctly downshifted to 8-bit.
---
 libavfilter/vf_thumbnail.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavfilter/vf_thumbnail.c b/libavfilter/vf_thumbnail.c
index 8cda7b45f1..728880e100 100644
--- a/libavfilter/vf_thumbnail.c
+++ b/libavfilter/vf_thumbnail.c
@@ -189,7 +189,7 @@ static void get_hist16(int *hist, const uint8_t *p, ptrdiff_t stride,
         }
         /* handle tail */
         for (int x = width4; x < width; x++)
-            hist[p16[x]]++;
+            hist[(uint8_t) (p16[x] >> shift)]++;
         p += stride;
     }
 
-- 
2.49.1