netdev - Re: x25: remote-triggerable heap overflow in call user data processing

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Message-ID: <1317620731.3802.50.camel@edumazet-laptop>
Date:	Mon, 03 Oct 2011 07:45:31 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	matt d <mattjd@...il.com>
Cc:	netdev@...r.kernel.org
Subject: Re: x25: remote-triggerable heap overflow in call user data
 processing

Le lundi 03 octobre 2011 à 16:23 +1300, matt d a écrit :
> Refer to the x25 packet layer's handling of incoming call user data,
> namely at these two locations, in x25_rx_call_request and
> x25_state1_machine:
> https://github.com/mirrors/linux/blob/master/net/x25/af_x25.c#L1039
> https://github.com/mirrors/linux/blob/master/net/x25/x25_in.c#L126
> 
> Call user data from an incoming message is copied into
> (make)x25->calluserdata.cuddata buffers, which are 128 bytes long.
> However, the length copied is based on the remaining message length,
> and is not limited to the output buffer size. This allows a remote
> attacker to overflow data onto the heap.
> 
> There is an appropriate constant defined for the length, but it
> seemingly isn't used there:
> https://github.com/mirrors/linux/blob/master/include/net/x25.h#L104
> 
> It seems this issue was noticed some time ago:
> http://www.spinics.net/lists/linux-x25/msg00043.html
> http://patchwork.ozlabs.org/patch/23917/
> ...however nothing was done about the bigger problem.
> 
> I have written a simple exploit for this vulnerability if it needs to
> be posted, however I think the problem is pretty straightforward to
> see as-is.

Please send a patch, it seems you have everything done to do it
properly ;)



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