[FFmpeg-cvslog] avformat/utils: Fix undefined behavior in ff_configure_buffers_for_index()

[Dale Curtis]

ffmpeg | branch: release/2.8 | Dale Curtis <dalecurtis at chromium.org> | Tue Jan 28 16:49:14 2020 -0800| [efaa2a05c0c68dc2404e7d977dc17a86e042701d] | committer: Michael Niedermayer

avformat/utils: Fix undefined behavior in ff_configure_buffers_for_index()

When e2_pts == INT64_MIN and e1_pts >= 0 the calculation of
e2_pts - e1_pts will overflow an int64_t.

Signed-off-by: Dale Curtis <dalecurtis at chromium.org>
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit f15007afa90a3eb3639848d9702c1cc3ac3e896b)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=efaa2a05c0c68dc2404e7d977dc17a86e042701d
---

 libavformat/utils.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/libavformat/utils.c b/libavformat/utils.c
index bc0dd21f09..084a3e7537 100644
--- a/libavformat/utils.c
+++ b/libavformat/utils.c
@@ -1796,6 +1796,8 @@ void ff_configure_buffers_for_index(AVFormatContext *s, int64_t time_tolerance)
     //We could use URLProtocol flags here but as many user applications do not use URLProtocols this would be unreliable
     const char *proto = avio_find_protocol_name(s->filename);
 
+    av_assert0(time_tolerance >= 0);
+
     if (!proto) {
         av_log(s, AV_LOG_INFO,
                "Protocol name not provided, cannot determine if input is local or "
@@ -1823,7 +1825,7 @@ void ff_configure_buffers_for_index(AVFormatContext *s, int64_t time_tolerance)
                 for (; i2 < st2->nb_index_entries; i2++) {
                     AVIndexEntry *e2 = &st2->index_entries[i2];
                     int64_t e2_pts = av_rescale_q(e2->timestamp, st2->time_base, AV_TIME_BASE_Q);
-                    if (e2_pts - e1_pts < time_tolerance)
+                    if (e2_pts < e1_pts || e2_pts - (uint64_t)e1_pts < time_tolerance)
                         continue;
                     pos_delta = FFMAX(pos_delta, e1->pos - e2->pos);
                     break;