[FFmpeg-cvslog] avcodec/zmbv: obtain frame later

[Michael Niedermayer]

ffmpeg | branch: release/4.0 | Michael Niedermayer <michael at niedermayer.cc> | Thu Feb 21 17:25:14 2019 +0100| [f32ce15f7c0beff43c060560de23daea2f353a7d] | committer: Michael Niedermayer

avcodec/zmbv: obtain frame later

The frame is not needed that early so obtaining it later avoids
the costly operation in case other checks fail.

Fixes: Timeout (14sec -> 4sec)
Fixes: 13140/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ZMBV_fuzzer-5738330308739072

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Reviewed-by: Tomas Härdin <tjoppen at acc.umu.se>
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit 177b40890c6de8c6896e0a1d4a631ea1ca89c044)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=f32ce15f7c0beff43c060560de23daea2f353a7d
---

 libavcodec/zmbv.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/libavcodec/zmbv.c b/libavcodec/zmbv.c
index b994e96e95..6ef549dff1 100644
--- a/libavcodec/zmbv.c
+++ b/libavcodec/zmbv.c
@@ -519,9 +519,6 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame, AVPac
         return AVERROR_INVALIDDATA;
     }
 
-    if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
-        return ret;
-
     if (c->comp == 0) { // uncompressed data
         if (c->decomp_size < len) {
             av_log(avctx, AV_LOG_ERROR, "Buffer too small\n");
@@ -547,6 +544,9 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame, AVPac
         av_log(avctx, AV_LOG_ERROR, "decompressed size %d is incorrect, expected %d\n", c->decomp_len, expected_size);
         return AVERROR_INVALIDDATA;
     }
+    if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
+        return ret;
+
     if (c->flags & ZMBV_KEYFRAME) {
         frame->key_frame = 1;
         frame->pict_type = AV_PICTURE_TYPE_I;