From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda3.sgi.com [192.48.176.15]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id p1EBhtac128611 for ; Mon, 14 Feb 2011 05:43:56 -0600 Date: Mon, 14 Feb 2011 22:46:29 +1100 From: Dave Chinner Subject: Re: [PATCH] xfs: prevent leaking uninitialized stack memory in FSGEOMETRY_V1 Message-ID: <20110214114629.GA13052@dastard> References: <1297347904.13370.9.camel@dan> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1297347904.13370.9.camel@dan> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: Dan Rosenberg Cc: security@kernel.org, linux-kernel@vger.kernel.org, xfs@oss.sgi.com, xfs-masters@oss.sgi.com, aelder@sgi.com, stable@kernel.org On Thu, Feb 10, 2011 at 09:25:04AM -0500, Dan Rosenberg wrote: > The FSGEOMETRY_V1 ioctl (and its compat equivalent) calls out to > xfs_fs_geometry() with a version number of 3. This code path does not > fill in the logsunit member of the passed xfs_fsop_geom_t, leading to > the leaking of four bytes of uninitialized stack data to potentially > unprivileged callers. Since all other members are filled in all code > paths and there are no padding bytes in this structure, it's safe to > avoid an expensive memset() in favor of just clearing this one field. If this really is a security problem, then it should use a memset. This is not a performance critical path and there are differences in the padding of the structure between 32 bit and 64 bit ioctl variants (it has a compat ioctl handler) and that can only be correctly handled by memset(). Also, using a memset means we won't have the problem of introducing new uninitialised fields or padding if we ever rev the structure again... Cheers, Dave. -- Dave Chinner david@fromorbit.com _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs