videodsp: assert that linesize is larger than width

Suggested-by: Andreas Cadhalpun <andreas.cadhalpun@googlemail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/videodsp_template.c

@@ -32,6 +32,8 @@ void FUNC(ff_emulated_edge_mc)(uint8_t *buf, const uint8_t *src,
     if (!w || !h)
         return;
 
+    av_assert2(block_w * sizeof(pixel) <= FFABS(buf_linesize));
+
     if (src_y >= h) {
         src -= src_y * src_linesize;
         src += (h - 1) * src_linesize;

libavcodec/x86/videodsp_init.c

@@ -162,6 +162,8 @@ static av_always_inline void emulated_edge_mc(uint8_t *dst, const uint8_t *src,
     if (!w || !h)
         return;
 
+    av_assert2(block_w <= FFABS(dst_stride));
+
     if (src_y >= h) {
         src -= src_y*src_stride;
         src_y_add = h - 1;