[FFmpeg-cvslog] avcodec/tiff: Update pointer only when the result is used

[Michael Niedermayer]

ffmpeg | branch: release/2.8 | Michael Niedermayer <michael at niedermayer.cc> | Thu Jun 22 20:21:05 2017 +0200| [be92b27024482579e42c767b2f5af319f932d0ec] | committer: Michael Niedermayer

avcodec/tiff: Update pointer only when the result is used

Fixes: runtime error: signed integer overflow: 538976288 * 32 cannot be represented in type 'int'
Fixes: 2310/clusterfuzz-testcase-minimized-4534784887881728

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 27f80ab0160d2e64007e1c9799ffd4504cc13eb5)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=be92b27024482579e42c767b2f5af319f932d0ec
---

 libavcodec/tiff.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/libavcodec/tiff.c b/libavcodec/tiff.c
index d026a5bd98..fcfa32dc8b 100644
--- a/libavcodec/tiff.c
+++ b/libavcodec/tiff.c
@@ -1288,6 +1288,8 @@ static int decode_frame(AVCodecContext *avctx,
         stride = p->linesize[plane];
         dst = p->data[plane];
         for (i = 0; i < s->height; i += s->rps) {
+            if (i)
+                dst += s->rps * stride;
             if (s->stripsizesoff)
                 ssize = ff_tget(&stripsizes, s->sstype, le);
             else
@@ -1308,7 +1310,6 @@ static int decode_frame(AVCodecContext *avctx,
                     return ret;
                 break;
             }
-            dst += s->rps * stride;
         }
         if (s->predictor == 2) {
             if (s->photometric == TIFF_PHOTOMETRIC_YCBCR) {