[FFmpeg-cvslog] avcodec/videodsp_template: Adjust pointers to avoid undefined pointer things

[Michael Niedermayer]

ffmpeg | branch: release/5.1 | Michael Niedermayer <michael at niedermayer.cc> | Thu Jan 12 00:29:02 2023 +0100| [ac3e0e7beb7f5d053691f378928cd6e97c2c95f5] | committer: Michael Niedermayer

avcodec/videodsp_template: Adjust pointers to avoid undefined pointer things

Fixes: subtraction of unsigned offset from 0xf6602770 overflowed to 0xf6638c80
Fixes: 48567/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_THEORA_fuzzer-495074400600064

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit f0150cd41c2d3c01050a6c4f3df1de511a217913)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=ac3e0e7beb7f5d053691f378928cd6e97c2c95f5
---

 libavcodec/videodsp_template.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/libavcodec/videodsp_template.c b/libavcodec/videodsp_template.c
index 324d70f2cb..d653f4d524 100644
--- a/libavcodec/videodsp_template.c
+++ b/libavcodec/videodsp_template.c
@@ -64,7 +64,7 @@ void FUNC(ff_emulated_edge_mc)(uint8_t *buf, const uint8_t *src,
     av_assert2(start_x < end_x && block_w);
 
     w    = end_x - start_x;
-    src += start_y * src_linesize + start_x * sizeof(pixel);
+    src += start_y * src_linesize + start_x * (ptrdiff_t)sizeof(pixel);
     buf += start_x * sizeof(pixel);
 
     // top
@@ -87,7 +87,7 @@ void FUNC(ff_emulated_edge_mc)(uint8_t *buf, const uint8_t *src,
         buf += buf_linesize;
     }
 
-    buf -= block_h * buf_linesize + start_x * sizeof(pixel);
+    buf -= block_h * buf_linesize + start_x * (ptrdiff_t)sizeof(pixel);
     while (block_h--) {
         pixel *bufp = (pixel *) buf;