[FFmpeg-cvslog] avcodec/mpeg12dec: Do not call show_bits() with invalid bits

[Michael Niedermayer]

ffmpeg | branch: release/2.7 | Michael Niedermayer <michael at niedermayer.cc> | Fri Nov  6 00:56:04 2015 +0100| [b0b1b208f5c7cd783b58cd1527f65b20ff550ffe] | committer: Michael Niedermayer

avcodec/mpeg12dec: Do not call show_bits() with invalid bits

Fixes assertion failure
Fixes: 63e50545709a6440d3d59f6426d58db9/signal_sigabrt_7ffff6ae7cc9_8189_3272a3010fd98ddf947c662bbde1ac13.ts

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit 973c3dba27d0b1a88c70f6661b6a90d2f2e50665)

Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=b0b1b208f5c7cd783b58cd1527f65b20ff550ffe
---

 libavcodec/mpeg12dec.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/mpeg12dec.c b/libavcodec/mpeg12dec.c
index 00ce2a4..fdb93e3 100644
--- a/libavcodec/mpeg12dec.c
+++ b/libavcodec/mpeg12dec.c
@@ -1928,7 +1928,7 @@ static int mpeg_decode_slice(MpegEncContext *s, int mb_y,
                     (left && show_bits(&s->gb, FFMIN(left, 23)) && !is_d10) ||
                     ((avctx->err_recognition & (AV_EF_BITSTREAM | AV_EF_AGGRESSIVE)) && left > 8)) {
                     av_log(avctx, AV_LOG_ERROR, "end mismatch left=%d %0X\n",
-                           left, show_bits(&s->gb, FFMIN(left, 23)));
+                           left, left>0 ? show_bits(&s->gb, FFMIN(left, 23)) : 0);
                     return AVERROR_INVALIDDATA;
                 } else
                     goto eos;