[FFmpeg-cvslog] avcodec/parser: Optimize ff_combine_frame() with massivly negative next

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Thu Aug  1 22:18:43 2019 +0200| [8a24d2cc304c7f0807bc472dfc39d247040d71c2] | committer: Michael Niedermayer

avcodec/parser: Optimize ff_combine_frame() with massivly negative next

Fixes: Timeout
Fixes: 15558/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_PPM_fuzzer-5705273643106304

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=8a24d2cc304c7f0807bc472dfc39d247040d71c2
---

 libavcodec/parser.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/libavcodec/parser.c b/libavcodec/parser.c
index 3e19810a94..a63f532c48 100644
--- a/libavcodec/parser.c
+++ b/libavcodec/parser.c
@@ -295,6 +295,10 @@ int ff_combine_frame(ParseContext *pc, int next,
         *buf      = pc->buffer;
     }
 
+    if (next < -8) {
+        pc->overread += -8 - next;
+        next = -8;
+    }
     /* store overread bytes */
     for (; next < 0; next++) {
         pc->state   = pc->state   << 8 | pc->buffer[pc->last_index + next];