[FFmpeg-cvslog] avcodec/ffv1dec: Check state transition table

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Thu Jun 21 22:10:23 2018 +0200| [84bbdc255a12cfe92c0a0c745245e3f85a23ae98] | committer: Michael Niedermayer

avcodec/ffv1dec: Check state transition table

Fixes: Timeout
Fixes: 8646/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_FFV1_fuzzer-5649968353247232

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=84bbdc255a12cfe92c0a0c745245e3f85a23ae98
---

 libavcodec/ffv1dec.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/libavcodec/ffv1dec.c b/libavcodec/ffv1dec.c
index 7658a51685..261e0cf70c 100644
--- a/libavcodec/ffv1dec.c
+++ b/libavcodec/ffv1dec.c
@@ -546,8 +546,14 @@ static int read_header(FFV1Context *f)
         f->ac = get_symbol(c, state, 0);
 
         if (f->ac == AC_RANGE_CUSTOM_TAB) {
-            for (i = 1; i < 256; i++)
-                f->state_transition[i] = get_symbol(c, state, 1) + c->one_state[i];
+            for (i = 1; i < 256; i++) {
+                int st = get_symbol(c, state, 1) + c->one_state[i];
+                if (st < 1 || st > 255) {
+                    av_log(f->avctx, AV_LOG_ERROR, "invalid state transition %d\n", st);
+                    return AVERROR_INVALIDDATA;
+                }
+                f->state_transition[i] = st;
+            }
         }
 
         colorspace          = get_symbol(c, state, 0); //YUV cs type