Re: Fw: [Bug 47021] New: kernel panic with l2tpv3 & mtu > 1500

From: Eric Dumazet <edumazet@google.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@bugzilla.kernel.org
To: shemminger@linux-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@linux-foundation.org
        ReportedBy: a1bert@atlas.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@google.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);