[FFmpeg-cvslog] avcodec/exr: skip bottom clearing loop when its outside the image

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Sun Oct 25 00:23:12 2020 +0200| [b0a8b40294ea212c1938348ff112ef1b9bf16bb3] | committer: Michael Niedermayer

avcodec/exr: skip bottom clearing loop when its outside the image

Fixes: signed integer overflow: 1633771809 * 32960 cannot be represented in type 'int'
Fixes: 26532/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_EXR_fuzzer-5613925708857344

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

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=b0a8b40294ea212c1938348ff112ef1b9bf16bb3
---

 libavcodec/exr.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/libavcodec/exr.c b/libavcodec/exr.c
index 8b701d1cd2..d233dd43fb 100644
--- a/libavcodec/exr.c
+++ b/libavcodec/exr.c
@@ -1842,13 +1842,14 @@ static int decode_frame(AVCodecContext *avctx, void *data,
 
     ymax = FFMAX(0, s->ymax + 1);
     // Zero out the end if ymax+1 is not h
-    for (i = 0; i < planes; i++) {
-        ptr = picture->data[i] + (ymax * picture->linesize[i]);
-        for (y = ymax; y < avctx->height; y++) {
-            memset(ptr, 0, out_line_size);
-            ptr += picture->linesize[i];
+    if (ymax < avctx->height)
+        for (i = 0; i < planes; i++) {
+            ptr = picture->data[i] + (ymax * picture->linesize[i]);
+            for (y = ymax; y < avctx->height; y++) {
+                memset(ptr, 0, out_line_size);
+                ptr += picture->linesize[i];
+            }
         }
-    }
 
     picture->pict_type = AV_PICTURE_TYPE_I;
     *got_frame = 1;