Re: CVE-2009-2903 kernel: appletalk: denial of service when handling IP tunnelled over DDP datagrams

[Willy Tarreau <w () 1wt eu>]

Hi Eugene,

On Mon, Sep 14, 2009 at 08:57:02AM +0800, Eugene Teo wrote:
> The check for the ipddpN device in the handle_ip_over_ddp() function 
> returns -NODEV to the atalk_rcv() function when the device does not 
> exist. The atalk_rcv() function then directly returns that value to its 
> caller. There is a missing call to kfree_skb() in these unaccepted 
> IP-DDP datagram that can exhaust the kernel memory eventually. It 
> affects Linux hosts with appletalk and ipddp modules loaded, that are 
> attached to the same link. Thanks to Mark Smith for reporting this issue 
> to us.
>
> net-next-2.6 commit:
> http://git.kernel.org/?p=linux/kernel/git/davem/net-next-2.6.git;a=commit;h=ffcfb8db540ff879c2a85bf7e404954281443414 
>
>
> Possible mitigation method:
> https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2009-2903#c3
>
> Reference:
> https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2009-2903
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;f=Documentation/networking/ipddp.txt;h=661a5558dd8e928f15771c07ef34b3ee9cb81e57;hb=HEAD
>
> Greg, this should go to -stable.

Davem generally handles his own -stable queue for the net subsystem
and submits fixes himself, but that's nice to notify about upcoming
patches in case it gets missed !

> Willy, this affects upstream 2.4 I believe.

Indeed, it seems so. I'm queuing it up for next release. I will have
to review it since the changes are not obvious. If you're aware of
any reproducer, I'd be glad to get it (in private) ; I'd like to at
least ensure I don't break the driver while trying to fix it !

Thanks!
Willy