netdev - Re: [PATCH] xfrm: fix xfrm_input/xfrm_tunnel

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Date:	Tue, 7 Apr 2015 14:32:57 +0200
From:	Steffen Klassert <steffen.klassert@...unet.com>
To:	Romain Francoise <romain@...bokech.com>
CC:	Alexey Dobriyan <adobriyan@...il.com>, <davem@...emloft.net>,
	<mike@...mi.net>, <netdev@...r.kernel.org>,
	<herbert@...dor.apana.org.au>
Subject: Re: [PATCH] xfrm: fix xfrm_input/xfrm_tunnel_check oops

On Tue, Apr 07, 2015 at 02:14:43PM +0200, Romain Francoise wrote:
> On Tue, Apr 07, 2015 at 02:43:41PM +0300, Alexey Dobriyan wrote:
> > On Tue, Apr 07, 2015 at 10:57:32AM +0200, Steffen Klassert wrote:
> >> On Thu, Apr 02, 2015 at 10:58:24AM +0300, Alexey Dobriyan wrote:
> >> > https://bugzilla.kernel.org/show_bug.cgi?id=95211
> >> > 
> >> > Commit 70be6c91c86596ad2b60c73587880b47df170a41
> >> > ("xfrm: Add xfrm_tunnel_skb_cb to the skb common buffer") added check
> >> > which dereferences ->outer_mode too early but larval SAs don't have
> >> > this pointer set (yet). So check for tunnel stuff later.
> >> > 
> >> > Mike Noordermeer reported this bug and patiently applied all the debugging.
> >> > 
> >> > Technically this is remote-oops-in-interrupt-context type of thing.
> >> > 
> >> > BUG: unable to handle kernel NULL pointer dereference at 0000000000000034
> >> > IP: [<ffffffff8150dca2>] xfrm_input+0x3c2/0x5a0
> >> > 	...
> >> > [<ffffffff81500fc6>] ? xfrm4_esp_rcv+0x36/0x70
> >> > [<ffffffff814acc9a>] ? ip_local_deliver_finish+0x9a/0x200
> >> > [<ffffffff81471b83>] ? __netif_receive_skb_core+0x6f3/0x8f0
> >> > 	...
> >> > 
> >> > RIP  [<ffffffff8150dca2>] xfrm_input+0x3c2/0x5a0
> >> > Kernel panic - not syncing: Fatal exception in interrupt
> >> > 
> >> > Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>
> >> 
> >> Good catch!
> >> 
> >> Applied to the ipsec tree, thanks everyone!
> 
> > For the record Mike confirmed that the patch works:
> > https://bugzilla.kernel.org/show_bug.cgi?id=95211#c20
> 
> Does this only affect configurations that use VTI? It's not clear from
> the description.

xfrm_tunnel_check() dereferences outer_mode only if it finds a tunnel
pointer, so it affects only vti SAs.
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