linux-kernel - Re: [PATCH v2] udf: udftime: prevent overflow in udf_disk_stamp_to

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Date: Wed, 10 Apr 2024 13:09:42 +0200
From: Jan Kara <jack@...e.cz>
To: Roman Smirnov <r.smirnov@....ru>
Cc: Jan Kara <jack@...e.com>, linux-kernel@...r.kernel.org,
	Sergey Shtylyov <s.shtylyov@....ru>, lvc-project@...uxtesting.org,
	Jan Kara <jack@...e.cz>
Subject: Re: [PATCH v2] udf: udftime: prevent overflow in
 udf_disk_stamp_to_time()

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@...e.cz>
> > Signed-off-by: Roman Smirnov <r.smirnov@....ru>
> 
> 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@...e.com>
SUSE Labs, CR