linux-kernel - Re: [PATCH 1/1] xfs: check for possible overflow in xfs_ioc

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 31 Jul 2012 07:49:46 +1000
From:	Dave Chinner <david@...morbit.com>
To:	Tomas Racek <tracek@...hat.com>
Cc:	linux-xfs@...r.kernel.org, lczerner@...hat.com,
	Ben Myers <bpm@....com>, Alex Elder <elder@...nel.org>,
	"supporter:XFS FILESYSTEM" <xfs@....sgi.com>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] xfs: check for possible overflow in xfs_ioc_trim

On Mon, Jul 30, 2012 at 10:13:44AM +0200, Tomas Racek wrote:
> If range.start argument was between ULLONG_MAX - BBSIZE and ULLONG_MAX,
> BTOBB macro resulted in overflow which caused start to be set to 0.
> Now, invalid argument error is returned instead.
> 
> Signed-off-by: Tomas Racek <tracek@...hat.com>
> ---
>  fs/xfs/xfs_discard.c |    4 ++++
>  1 files changed, 4 insertions(+), 0 deletions(-)
> 
> diff --git a/fs/xfs/xfs_discard.c b/fs/xfs/xfs_discard.c
> index f9c3fe3..0ef7dd4 100644
> --- a/fs/xfs/xfs_discard.c
> +++ b/fs/xfs/xfs_discard.c
> @@ -179,6 +179,10 @@ xfs_ioc_trim(
>  	 * used by the fstrim application.  In the end it really doesn't
>  	 * matter as trimming blocks is an advisory interface.
>  	 */
> +
> +	if (range.start > ULLONG_MAX - BBSIZE)
> +		return -XFS_ERROR(EINVAL);
> +

There's no point checking for overflow on the range start - what we
need to check is whether it is larger than the size of the
filesystem. We do that after the conversion of range.start to basic
blocks, so that check needs to be promoted to before this. i.e.

	if (range.start >= XFS_FSB_TO_B(mp, mp->m_sb.sb_dblocks))
		return -XFS_ERROR(EINVAL);

>  	start = BTOBB(range.start);
>  	end = start + BTOBBT(range.len) - 1;
>  	minlen = BTOBB(max_t(u64, granularity, range.minlen));

And that will prevent the overflow in BTOBB() just as effectively...

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/