linux-kernel - Re: [PATCH] xfrm_user: return error pointer instead of NULL

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Message-ID: <CA+rthh8D9oZMC9hwQkowMneb-wFG+fUoSnaD9g_auTCG0TBrWg@mail.gmail.com>
Date:	Mon, 17 Sep 2012 22:15:33 +0200
From:	Mathias Krause <minipli@...glemail.com>
To:	Steffen Klassert <steffen.klassert@...unet.com>
Cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] xfrm_user: return error pointer instead of NULL

On Mon, Sep 17, 2012 at 9:16 AM, Steffen Klassert
<steffen.klassert@...unet.com> wrote:
> On Thu, Sep 13, 2012 at 11:41:26PM +0200, Mathias Krause wrote:
>> When dump_one_state() returns an error, e.g. because of a too small
>> buffer to dump the whole xfrm state, xfrm_state_netlink() returns NULL
>> instead of an error pointer. But its callers expect an error pointer
>> and therefore continue to operate on a NULL skbuff.
>>
>> This could lead to a privilege escalation (execution of user code in
>> kernel context) if the attacker has CAP_NET_ADMIN and is able to map
>> address 0.
>
> Or it simply crashes with a NULL pointer dereference.

..while holding the xfrm_cfg_mutex, therefore effectively disabling
the XFRM netlink interface. So it's at least a DOS in that case ;)

Regards,
Mathias
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