From: Dave Chinner <david@fromorbit.com>
To: Eric Sandeen <sandeen@sandeen.net>
Cc: Jeffrey Hundstad <jeffrey.hundstad@mnsu.edu>, xfs@oss.sgi.com
Subject: Re: kernel panic - stack-protector: kernel stack is corrupted in: f87aca93
Date: Tue, 1 Mar 2011 13:57:26 +1100 [thread overview]
Message-ID: <20110301025726.GF3087@dastard> (raw)
In-Reply-To: <4D6C4CC5.5030909@sandeen.net>
On Mon, Feb 28, 2011 at 07:32:53PM -0600, Eric Sandeen wrote:
> On 2/28/11 7:03 PM, Jeffrey Hundstad wrote:
> > Sadly, I didn't have the vmlinux file around anymore. I'll be glad to recreate it when I get in tomorrow. However, I have revered commit 3a3675b7f23f83ca8c67c9c2b6edf707fd28d1ba and the problem seems to have vanished. I'm guessing the stack at this point is a little to fragile for a memset. The patch is:
>
> Ok, no worries, if the below commit is the culprit for sure, that's enough...
>
> So, whoopsies.
>
> STATIC int
> xfs_ioc_fsgeometry_v1(
> xfs_mount_t *mp,
> void __user *arg)
> {
> xfs_fsop_geom_v1_t fsgeo;
> int error;
>
> error = xfs_fs_geometry(mp, (xfs_fsop_geom_t *)&fsgeo, 3);
>
> what we really have is an xfs_fsop_geom_v1_t, but cast to a xfs_fsop_geom_t.
>
> xfs_fs_geometry() zeroes it out to the tune of sizeof (xfs_fsop_geom_t)
>
> the latter is bigger, with the addition of
>
> __u32 logsunit;
>
> so we overwrite memory that's not ours. :( Seems like we should zero
> in the callers, when we know how much is really on the stack. I'll follow
> up with a patch; pity this one was fast-tracked for security, I think :(
Fmeh - the differences in structure size, alignment and padding on
different platforms was why I suggested that memset() is a
preferable fix to just setting a single field. I didn't look any
further at the patch before it was committed so I didn't catch the
fact that it was busted in the first place...
Just another example of Occam's Eraser(*) in action, I'd say.
Cheers,
Dave
(*) From the Fortune Cookie database:
OCCAM'S ERASER:
The philosophical principle that even the simplest solution is
bound to have something wrong with it.
--
Dave Chinner
david@fromorbit.com
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next prev parent reply other threads:[~2011-03-01 2:54 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-28 22:58 kernel panic - stack-protector: kernel stack is corrupted in: f87aca93 Jeffrey Hundstad
2011-03-01 0:00 ` Eric Sandeen
2011-03-01 1:03 ` Jeffrey Hundstad
2011-03-01 1:32 ` Eric Sandeen
2011-03-01 2:57 ` Dave Chinner [this message]
2011-03-01 1:37 ` [PATCH] xfs: zero proper structure size for geometry calls Eric Sandeen
2011-03-01 2:59 ` Dave Chinner
2011-03-01 3:01 ` Eric Sandeen
2011-03-01 6:59 ` [PATCH V2] " Eric Sandeen
2011-03-01 12:55 ` Dan Rosenberg
2011-03-01 15:36 ` Jeffrey Hundstad
2011-03-01 15:49 ` Eric Sandeen
2011-03-01 17:50 ` [PATCH, V3 (sort of)] " Alex Elder
2011-03-01 18:18 ` Eric Sandeen
2011-03-01 21:40 ` Jeffrey Hundstad
2011-03-02 0:02 ` Dave Chinner
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