[FFmpeg-devel] [PATCH 2/2] avcodec/zmbv: Check that the decompressed data is large enough to contain MVs or an intra frame

[Michael Niedermayer]

Fixes: Timeout
Fixes: 10182/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ZMBV_fuzzer-6245951174344704

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
---
 libavcodec/zmbv.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/libavcodec/zmbv.c b/libavcodec/zmbv.c
index 177993d0a6..0c2daf47c2 100644
--- a/libavcodec/zmbv.c
+++ b/libavcodec/zmbv.c
@@ -409,6 +409,7 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame, AVPac
     int zret = Z_OK; // Zlib return code
     int len = buf_size;
     int hi_ver, lo_ver, ret;
+    int min_size;
 
     /* parse header */
     if (len < 1)
@@ -510,7 +511,11 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame, AVPac
         memset(c->prev, 0, avctx->width * avctx->height * (c->bpp / 8));
         c->decode_intra= decode_intra;
     }
-
+    if (c->flags & ZMBV_KEYFRAME) {
+        min_size = avctx->width * avctx->height * (c->bpp / 8);
+    } else {
+        min_size = (c->bx * c->by * 2 + 3) & ~3;
+    }
     if (!c->decode_intra) {
         av_log(avctx, AV_LOG_ERROR, "Error! Got no format or no keyframe!\n");
         return AVERROR_INVALIDDATA;
@@ -539,6 +544,10 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame, AVPac
         }
         c->decomp_len = c->zstream.total_out;
     }
+    if (min_size > c->decomp_len) {
+        av_log(avctx, AV_LOG_ERROR, "input too small\n");
+        return AVERROR_INVALIDDATA;
+    }
     if (c->flags & ZMBV_KEYFRAME) {
         frame->key_frame = 1;
         frame->pict_type = AV_PICTURE_TYPE_I;
-- 
2.18.0