vf_unsharp: fix out-of-buffer read

In apply_unsharp(), when y is >= height, prevent out-of-buffer reading
from src, read from the last buffer line in src2 instead.

The check was implemented in the original unsharp libmpcodecs code and
lost in the port.

This also fixes output discrepancy between the two filters.

1 files changed, 5 insertions, 1 deletions

diff --git a/libavfilter/vf_unsharp.c b/libavfilter/vf_unsharp.c
index bdbfd304e2..ce728283d0 100644
--- a/libavfilter/vf_unsharp.c
+++ b/libavfilter/vf_unsharp.c
@@ -73,6 +73,7 @@ static void apply_unsharp(      uint8_t *dst, int dst_stride,
 
     int32_t res;
     int x, y, z;
+    const uint8_t *src2;
 
     if (!fp->amount) {
         if (dst_stride == src_stride)
@@ -87,9 +88,12 @@ static void apply_unsharp(      uint8_t *dst, int dst_stride,
         memset(sc[y], 0, sizeof(sc[y][0]) * (width + 2 * fp->steps_x));
 
     for (y = -fp->steps_y; y < height + fp->steps_y; y++) {
+        if (y < height)
+            src2 = src;
+
         memset(sr, 0, sizeof(sr[0]) * (2 * fp->steps_x - 1));
         for (x = -fp->steps_x; x < width + fp->steps_x; x++) {
-            tmp1 = x <= 0 ? src[0] : x >= width ? src[width-1] : src[x];
+            tmp1 = x <= 0 ? src2[0] : x >= width ? src2[width-1] : src2[x];
             for (z = 0; z < fp->steps_x * 2; z += 2) {
                 tmp2 = sr[z + 0] + tmp1; sr[z + 0] = tmp1;
                 tmp1 = sr[z + 1] + tmp2; sr[z + 1] = tmp2;