Re: [PATCH v2] udf: udftime: prevent overflow in udf_disk_stamp_to_time()

From: Jan Kara
Date: Wed Apr 10 2024 - 07:09:52 EST


On Wed 10-04-24 13:04:06, Jan Kara wrote:
> On Wed 27-03-24 16:27:55, Roman Smirnov wrote:
> > An overflow can occur in a situation where src.centiseconds
> > takes the value of 255. This situation is unlikely, but there
> > is no validation check anywere in the code.
> >
> > Found by Linux Verification Center (linuxtesting.org) with Svace.
> >
> > Suggested-by: Jan Kara <jack@xxxxxxx>
> > Signed-off-by: Roman Smirnov <r.smirnov@xxxxxx>
>
> Thanks! I've added the patch to my tree.

Actually, there's a small typo that needed fixing up. Corrected on commit.

> > diff --git a/fs/udf/udftime.c b/fs/udf/udftime.c
> > index 758163af39c2..3113785af3cf 100644
> > --- a/fs/udf/udftime.c
> > +++ b/fs/udf/udftime.c
> > @@ -46,13 +46,18 @@ udf_disk_stamp_to_time(struct timespec64 *dest, struct timestamp src)
> > dest->tv_sec = mktime64(year, src.month, src.day, src.hour, src.minute,
> > src.second);
> > dest->tv_sec -= offset * 60;
> > - dest->tv_nsec = 1000 * (src.centiseconds * 10000 +
> > - src.hundredsOfMicroseconds * 100 + src.microseconds);
> > +
> > /*
> > * Sanitize nanosecond field since reportedly some filesystems are
> > * recorded with bogus sub-second values.
> > */
> > - dest->tv_nsec %= NSEC_PER_SEC;
> > + if (src.centiseconds < 100 && src.hundredsOfMicroseconds < 100 &&
> > + src.microseconds < 100) {
> > + dest->tv_nsec = 1000 * (src.centiseconds * 10000 +
> > + src.hundredsOfMicroseconds * 100 + src.microseconds);
> > + } else {
> > + desk->tv_nsec = 0;
^^^^ Here

> > + }
> > }

Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR