Openwall GNU/*/Linux - a small security-enhanced Linux distro for servers
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Mon, 21 Sep 2015 17:50:17 +0200
From: Salvatore Bonaccorso <carnil@...ian.org>
To: oss-security@...ts.openwall.com
Cc: sfjro@...rs.sourceforge.net
Subject: Re: CVE request: Use-after-free in Linux kernel with
 aufs mmap patch

Hi

On Thu, Sep 10, 2015 at 08:26:30PM +0100, Ben Hutchings wrote:
> The aufs (Advanced Union Filesystem) project provides an optional patch
> for the Linux kernel, called either aufs3-mmap.patch or
> aufs4-mmap.patch, which is needed to ensure correct behaviour of
> memory-mapped files from an aufs mount.
> 
> Each memory mapping (vma) holds a reference to the file that is mapped.
> This patch makes it also hold a reference to the virtual file on the
> union mount through which the file was found, where applicable.
> 
> In two functions, madvise_remove() and sys_msync(), it is necessary to
> take an extra reference to the mapped file before unlocking the current
> memory management state, as the vma may be freed after that point.
> Unfortunately the aufs patch introduces later uses of the vma, resulting
> in a potential use-after-free.  This is certainly exploitable for a
> minor denial of service (BUG in process context, so the task can't be
> cleaned up properly but the system does not panic) but might also be
> usable for privilege escalation.
> 
> I posted a patch here that works for me:
> http://sourceforge.net/p/aufs/mailman/message/34449209/
> 
> Please assign a CVE ID to this.

Adding MITRE's CVE assignment team to CC.

Can you assign a CVE for this issue?
http://www.openwall.com/lists/oss-security/2015/09/18/10 confirms that
Ben Hutchins' patch fixes the issue.

Regards,
Salvatore

Powered by blists - more mailing lists

Your e-mail address:

Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.