[FFmpeg-cvslog] avformat/mov: do not set sign bit for chunk_offsets

[Michael Niedermayer]

ffmpeg | branch: release/4.2 | Michael Niedermayer <michael at niedermayer.cc> | Fri Dec 15 22:37:49 2023 +0100| [4ace000985eb0e3e403af2aeab008b2414b14a2b] | committer: Michael Niedermayer

avformat/mov: do not set sign bit for chunk_offsets

Fixes: signed integer overflow: 2314885530818453536 - -7412889664301817824 cannot be represented in type 'long'
Fixes: 64296/clusterfuzz-testcase-minimized-ffmpeg_dem_MOV_fuzzer-6304027146846208

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit cfc0a68d4d3192779e356a852e71b8218e7a00ab)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=4ace000985eb0e3e403af2aeab008b2414b14a2b
---

 libavformat/mov.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/libavformat/mov.c b/libavformat/mov.c
index 206138707d..b8828041d7 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -2028,8 +2028,13 @@ static int mov_read_stco(MOVContext *c, AVIOContext *pb, MOVAtom atom)
         for (i = 0; i < entries && !pb->eof_reached; i++)
             sc->chunk_offsets[i] = avio_rb32(pb);
     else if (atom.type == MKTAG('c','o','6','4'))
-        for (i = 0; i < entries && !pb->eof_reached; i++)
+        for (i = 0; i < entries && !pb->eof_reached; i++) {
             sc->chunk_offsets[i] = avio_rb64(pb);
+            if (sc->chunk_offsets[i] < 0) {
+                av_log(c->fc, AV_LOG_WARNING, "Impossible chunk_offset\n");
+                sc->chunk_offsets[i] = 0;
+            }
+        }
     else
         return AVERROR_INVALIDDATA;