[FFmpeg-cvslog] avformat/mpc8: correct integer overflow in mpc8_parse_seektable()

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Fri Oct 30 21:50:32 2020 +0100| [0897402ac8a2045691395380a9fd2ea88c0d3798] | committer: Michael Niedermayer

avformat/mpc8: correct integer overflow in mpc8_parse_seektable()

Fixes: signed integer overflow: -4683718486770919638 * 2 cannot be represented in type 'long'
Fixes: 26704/clusterfuzz-testcase-minimized-ffmpeg_dem_MPC8_fuzzer-6327056939614208
Fixes: 27550/clusterfuzz-testcase-minimized-ffmpeg_dem_MPC8_fuzzer-6259212652642304

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=0897402ac8a2045691395380a9fd2ea88c0d3798
---

 libavformat/mpc8.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavformat/mpc8.c b/libavformat/mpc8.c
index 2b5eefe8c3..a7ad908ca4 100644
--- a/libavformat/mpc8.c
+++ b/libavformat/mpc8.c
@@ -182,7 +182,7 @@ static void mpc8_parse_seektable(AVFormatContext *s, int64_t off)
         t += get_bits(&gb, 12);
         if(t & 1)
             t = -(t & ~1);
-        pos = (t >> 1) + ppos[0]*2 - ppos[1];
+        pos = (t >> 1) + (uint64_t)ppos[0]*2 - ppos[1];
         av_add_index_entry(s->streams[0], pos, (int64_t)i << seekd, 0, 0, AVINDEX_KEYFRAME);
         ppos[1] = ppos[0];
         ppos[0] = pos;