[FFmpeg-devel] [PATCH] avformat/mov: fix integer overflow

Ganesh Ajjanagadde gajjanagadde at gmail.com
Sat Oct 10 19:51:10 CEST 2015

Partially fixes Ticket 4727.

-duration is not a safe expression, since duration can be INT_MIN.
One might ask how it can become INT_MIN.
Although it is true that line 2574 is no longer reached with INT_MIN due
to commit 053e80f6eaf8d87521fe58ea96886b6ee0bbe59d (which fixed another
integer overflow issue), mov_update_dts_shift is called on line 3549 as
well, right after a read of untrusted data.
One can do the fix locally there, but that function is already a huge
mess. Changing mov_update_dts_shift is likely better.

This changes duration to INT_MIN + 1 in such cases. This should not make any
practical difference since such streams are anyway fuzzer files.

Tested with FATE.

Signed-off-by: Ganesh Ajjanagadde <gajjanagadde at gmail.com>
 libavformat/mov.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/libavformat/mov.c b/libavformat/mov.c
index 4c073a3..87b46cf 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -2521,6 +2521,8 @@ static int mov_read_stts(MOVContext *c, AVIOContext *pb, MOVAtom atom)
 static void mov_update_dts_shift(MOVStreamContext *sc, int duration)
     if (duration < 0) {
+        if (duration == INT_MIN)
+            duration++;
         sc->dts_shift = FFMAX(sc->dts_shift, -duration);

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