[FFmpeg-cvslog] avcodec/imm4: Unreference previous frame on frame size change

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Sat Mar  9 22:22:55 2019 +0100| [0be0197f49a5ac78c0f8be34fe66dd7657c83c23] | committer: Michael Niedermayer

avcodec/imm4: Unreference previous frame on frame size change

Fixes: Out of array access
Fixes: 13552/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_IMM4_fuzzer-5767949648920576

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

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=0be0197f49a5ac78c0f8be34fe66dd7657c83c23
---

 libavcodec/imm4.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/libavcodec/imm4.c b/libavcodec/imm4.c
index b66689acab..1a4d0decd7 100644
--- a/libavcodec/imm4.c
+++ b/libavcodec/imm4.c
@@ -446,11 +446,13 @@ static int decode_frame(AVCodecContext *avctx, void *data,
         return AVERROR_PATCHWELCOME;
     }
 
-    if (!frame->key_frame &&
-        (avctx->width != width ||
-         avctx->height != height)) {
-        av_log(avctx, AV_LOG_ERROR, "Frame size change is unsupported.\n");
-        return AVERROR_INVALIDDATA;
+    if (avctx->width  != width ||
+        avctx->height != height) {
+        if (!frame->key_frame) {
+            av_log(avctx, AV_LOG_ERROR, "Frame size change is unsupported.\n");
+            return AVERROR_INVALIDDATA;
+        }
+        av_frame_unref(s->prev_frame);
     }
 
     ret = ff_set_dimensions(avctx, width, height);