[FFmpeg-cvslog] avcodec/dirac_parser: Check that there is a previous PU before accessing it

[Michael Niedermayer]

ffmpeg | branch: release/2.7 | Michael Niedermayer <michael at niedermayer.cc> | Sat Dec  5 17:15:38 2015 +0100| [d17298b666bcbaba2931d98a292c866c29cc94da] | committer: Michael Niedermayer

avcodec/dirac_parser: Check that there is a previous PU before accessing it

Fixes out of array read
Fixes: 99d142c47e6ba3510a74b872a1a2ae72/asan_heap-oob_11b36f4_3811_0f5c69e7609a88a580135678de1df844.dxa

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit a08681f1e614152184615e2bcd71c3d63835f810)

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

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=d17298b666bcbaba2931d98a292c866c29cc94da
---

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

diff --git a/libavcodec/dirac_parser.c b/libavcodec/dirac_parser.c
index c7c4b69..1ca7e31 100644
--- a/libavcodec/dirac_parser.c
+++ b/libavcodec/dirac_parser.c
@@ -201,7 +201,7 @@ static int dirac_combine_frame(AVCodecParserContext *s, AVCodecContext *avctx,
         }
 
         /* Get the picture number to set the pts and dts*/
-        if (parse_timing_info) {
+        if (parse_timing_info && pu1.prev_pu_offset >= 13) {
             uint8_t *cur_pu = pc->buffer +
                               pc->index - 13 - pu1.prev_pu_offset;
             int pts = AV_RB32(cur_pu + 13);