netdev - Re: Fw: [Bug 47021] New: kernel panic with l2tpv3 & mtu

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Date:	Tue, 04 Sep 2012 21:52:14 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Stephen Hemminger <shemminger@...tta.com>
Cc:	netdev@...r.kernel.org, a1bert@...as.cz
Subject: Re: Fw: [Bug 47021] New: kernel panic with l2tpv3 & mtu > 1500

From: Eric Dumazet <edumazet@...gle.com>

On Tue, 2012-09-04 at 09:07 -0700, Stephen Hemminger wrote:
> 
> Begin forwarded message:
> 
> Date: Tue,  4 Sep 2012 16:06:06 +0000 (UTC)
> From: bugzilla-daemon@...zilla.kernel.org
> To: shemminger@...ux-foundation.org
> Subject: [Bug 47021] New: kernel panic with l2tpv3 & mtu > 1500
> 
> 
> https://bugzilla.kernel.org/show_bug.cgi?id=47021
> 
>            Summary: kernel panic with l2tpv3 & mtu > 1500
>            Product: Networking
>            Version: 2.5
>     Kernel Version: 3.2.28
>           Platform: All
>         OS/Version: Linux
>               Tree: Mainline
>             Status: NEW
>           Severity: normal
>           Priority: P1
>          Component: Other
>         AssignedTo: shemminger@...ux-foundation.org
>         ReportedBy: a1bert@...as.cz
>         Regression: No
> 
> 
> first l2tpv3 packet that enters physical device with MTU > 1500 causes kernel
> panic
> 
> tunel created using:
> 
> l2tpv3tun add tunnel tunnel_id 1 peer_tunnel_id 1 encap udp udp_sport 5001
> udp_dport 5001 local 192.168.1.1 remote 192.168.1.2
> 
> l2tpv3tun add session tunnel_id 1 session_id 1 peer_session_id 1 dev l2tpeth1
> 
> 
> reproducible: always
> 

Seems following patch is needed, not sure if it helps

[PATCH] l2tp: fix a typo in l2tp_eth_dev_recv()

While investigating l2tp bug, I hit a bug in eth_type_trans(),
because not enough bytes were pulled in skb head.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/l2tp/l2tp_eth.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/l2tp/l2tp_eth.c b/net/l2tp/l2tp_eth.c
index f9ee74d..3bfb34a 100644
--- a/net/l2tp/l2tp_eth.c
+++ b/net/l2tp/l2tp_eth.c
@@ -153,7 +153,7 @@ static void l2tp_eth_dev_recv(struct l2tp_session *session, struct sk_buff *skb,
 		print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, skb->data, length);
 	}
 
-	if (!pskb_may_pull(skb, sizeof(ETH_HLEN)))
+	if (!pskb_may_pull(skb, ETH_HLEN))
 		goto error;
 
 	secpath_reset(skb);


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