[FFmpeg-cvslog] lavfi/perlin: Fix out of bounds stack buffer write

[Marvin Scholz]

ffmpeg | branch: master | Marvin Scholz <epirat07 at gmail.com> | Tue Jul  2 20:38:00 2024 +0200| [6d9c4bd69e81b614cf1e1a809679a7ab840b2b3d] | committer: Michael Niedermayer

lavfi/perlin: Fix out of bounds stack buffer write

An incorrect calculation in ff_perlin_init causes a write to the
stack array at index 256, which is out of bounds.

Fixes: CID1608711
Reviewed-by: Stefano Sabatini <stefasab at gmail.com>
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=6d9c4bd69e81b614cf1e1a809679a7ab840b2b3d
---

 libavfilter/perlin.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavfilter/perlin.c b/libavfilter/perlin.c
index 09bae7ad33..ffad8c1e4e 100644
--- a/libavfilter/perlin.c
+++ b/libavfilter/perlin.c
@@ -129,7 +129,7 @@ int ff_perlin_init(FFPerlin *perlin, double period, int octaves, double persiste
         for (i = 0; i < 256; i++) {
             unsigned int random_idx = av_lfg_get(&lfg) % (256-i);
             uint8_t random_val = random_permutations[random_idx];
-            random_permutations[random_idx] = random_permutations[256-i];
+            random_permutations[random_idx] = random_permutations[255-i];
 
             perlin->permutations[i] = perlin->permutations[i+256] = random_val;
         }