[FFmpeg-cvslog] avformat/mov: Check offset addition for overflow

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Wed Mar 17 13:31:28 2021 +0100| [92fde2585e98b83143e84fd2899148990f594c3f] | committer: Michael Niedermayer

avformat/mov: Check offset addition for overflow

Fixes: signed integer overflow: 9223372036854775807 + 536870912 cannot be represented in type 'long'
Fixes: 31678/clusterfuzz-testcase-minimized-ffmpeg_dem_MOV_fuzzer-5614204619980800

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=92fde2585e98b83143e84fd2899148990f594c3f
---

 libavformat/mov.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/libavformat/mov.c b/libavformat/mov.c
index 97857789f4..f9c4dbe5d4 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -5051,6 +5051,7 @@ static int mov_read_sidx(MOVContext *c, AVIOContext *pb, MOVAtom atom)
     int64_t stream_size = avio_size(pb);
     int64_t offset = av_sat_add64(avio_tell(pb), atom.size), pts, timestamp;
     uint8_t version, is_complete;
+    int64_t offadd;
     unsigned i, j, track_id, item_count;
     AVStream *st = NULL;
     AVStream *ref_st = NULL;
@@ -5088,11 +5089,15 @@ static int mov_read_sidx(MOVContext *c, AVIOContext *pb, MOVAtom atom)
 
     if (version == 0) {
         pts = avio_rb32(pb);
-        offset += avio_rb32(pb);
+        offadd= avio_rb32(pb);
     } else {
         pts = avio_rb64(pb);
-        offset += avio_rb64(pb);
+        offadd= avio_rb64(pb);
     }
+    if (av_sat_add64(offset, offadd) != offset + (uint64_t)offadd)
+        return AVERROR_INVALIDDATA;
+
+    offset += (uint64_t)offadd;
 
     avio_rb16(pb); // reserved
 
@@ -5115,6 +5120,8 @@ static int mov_read_sidx(MOVContext *c, AVIOContext *pb, MOVAtom atom)
         if (frag_stream_info)
             frag_stream_info->sidx_pts = timestamp;
 
+        if (av_sat_add64(offset, size) != offset + size)
+            return AVERROR_INVALIDDATA;
         offset += size;
         pts += duration;
     }