[FFmpeg-devel] [PATCH] Avoid undefined behavior by limiting PTS to 62 bits in ogg decoder

[Fredrik Hubinette]

Not sure how to update the commit message.
The undefined behavior occurs in av_add_stable, which is called from
compute_packet_fields.
In that code PTS can be equal to -(1<<63), which then causes a int64_t to
overflow.

On Wed, Jul 18, 2018 at 4:04 AM Michael Niedermayer <michael at niedermayer.cc>
wrote:

> On Mon, Jul 16, 2018 at 04:32:14PM -0700, Fredrik Hubinette wrote:
> > With some (garbled) OGG data, PTS can overflow causing undefined
> behavior.
> > This patch avoids that by zeroing out PTS values greater than 2^62.
>
> >  oggdec.h |    3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > ff003b78842c7724ccc1a42f9584b1f8aa0b0b3d
> 0001-Avoid-undefined-behavior-by-limiting-PTS-to-62-bits-.patch
> > From 26a8582bc04f5bddc037ffcce99025e2f977abe0 Mon Sep 17 00:00:00 2001
> > From: Fredrik Hubinette <hubbe at google.com>
> > Date: Mon, 16 Jul 2018 14:54:43 -0700
> > Subject: [PATCH] Avoid undefined behavior by limiting PTS to 62 bits in
> ogg
> >  decoder
> >
> > ---
> >  libavformat/oggdec.h | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
>
> I think someone reading this commit message would like to know more
> about where that undefined behaviour occurs and how this is guranteeing
> to fix it
>
>
> [...]
>
> --
> Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
>
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>
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