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Date: Fri, 1 Oct 2010 14:31:12 -0700
From: Joel Becker <>
To: Eugene Teo <>
Cc: oss-security <>,
Subject: Re: Small exposure in ocfs2 fast symlinks.

On Thu, Sep 30, 2010 at 10:32:14PM +0800, Eugene Teo wrote:
> On 09/30/2010 01:49 PM, Joel Becker wrote:
> >On Wed, Sep 29, 2010 at 08:30:09PM -0700, Greg KH wrote:
> >>On Wed, Sep 29, 2010 at 07:04:07PM -0700, Joel Becker wrote:
> >>>Hey Everyone,
> >>>	We just discovered that ocfs2 could walk off the end of fast
> >>>symlinks -- that is, symlinks that are stored directly in the inode
> >>>block.  ocfs2 terminates these with NUL characters, but a disk
> >>>corruption or an attacker with direct access to the ocfs2 disk could
> >>>overwrite the NUL.  Following the symlink via the filesystem would walk
> >>>off the end of the in-memory block buffer.  We're not sure how
> >>>exploitable this is, but I figured I'd provide a heads-up.  The fix is
> >>>in ocfs2's git tree and will be sent upstream tonight.  Erratas with the
> >>>fix are being built.
> >>
> >>Care to send the git commit id to the tree when it
> >>hits Linus's tree so it gets backported there?
> >
> >	I Cc'd in the commit, don't worry ;-)
> Thanks, please also cc oss-sec when the commit hash is available.

	The commit hash in Linus's tree is
1fc8a117865b54590acd773a55fbac9221b018f0.  This problem only exists from
2.6.30 onwards; it is not present in older kernels.



"In the long run...we'll all be dead."

Joel Becker
Consulting Software Developer
Phone: (650) 506-8127

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