[FFmpeg-cvslog] avcodec/hevc_cabac: Check prefix so as to avoid invalid shifts in coeff_abs_level_remaining_decode()

[Michael Niedermayer]

ffmpeg | branch: release/3.3 | Michael Niedermayer <michael at niedermayer.cc> | Mon Jan 15 23:46:44 2018 +0100| [aec30d0da9dc66de0d05b0c9d65022611bbf3f9b] | committer: Michael Niedermayer

avcodec/hevc_cabac: Check prefix so as to avoid invalid shifts in coeff_abs_level_remaining_decode()

I suspect that this can be limited tighter, but i failed to find anything
in the spec that would confirm that.

Fixes: 4833/clusterfuzz-testcase-minimized-5302840101699584
Fixes: runtime error: left shift of 134217730 by 4 places cannot be represented in type 'int'

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit a026a3efaeb9c2026668dccbbda339a21ab3206b)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=aec30d0da9dc66de0d05b0c9d65022611bbf3f9b
---

 libavcodec/hevc_cabac.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/hevc_cabac.c b/libavcodec/hevc_cabac.c
index 5e46c59a24..29485dc64c 100644
--- a/libavcodec/hevc_cabac.c
+++ b/libavcodec/hevc_cabac.c
@@ -987,7 +987,7 @@ static av_always_inline int coeff_abs_level_remaining_decode(HEVCContext *s, int
     } else {
         int prefix_minus3 = prefix - 3;
 
-        if (prefix == CABAC_MAX_BIN) {
+        if (prefix == CABAC_MAX_BIN || prefix_minus3 + rc_rice_param >= 31) {
             av_log(s->avctx, AV_LOG_ERROR, "CABAC_MAX_BIN : %d\n", prefix);
             return 0;
         }