From 6af88da14ee284aaad6e4326da09a89191ab6165 Mon Sep 17 00:00:00 2001
From: "David S. Miller" <davem@davemloft.net>
Date: Sun, 8 May 2011 13:45:20 -0700
Subject: [PATCH] l2tp: Fix locking in l2tp_core.c
l2tp_xmit_skb() must take the socket lock. It makes use of ip_queue_xmit()
which expects to execute in a socket atomic context.
Since we execute this function in software interrupts, we cannot use the
usual lock_sock()/release_sock() sequence, instead we have to use
bh_lock_sock() and see if a user has the socket locked, and if so drop
the packet.
Signed-off-by: David S. Miller <davem@davemloft.net>
---
net/l2tp/l2tp_core.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index c64ce0a0bb03..78530299ae38 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -1060,6 +1060,12 @@ int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb, int hdr_len
IPSKB_REROUTED);
nf_reset(skb);
+ bh_lock_sock(sk);
+ if (sock_owned_by_user(sk)) {
+ dev_kfree_skb(skb);
+ goto out_unlock;
+ }
+
/* Get routing info from the tunnel socket */
skb_dst_drop(skb);
skb_dst_set(skb, dst_clone(__sk_dst_get(sk)));
@@ -1106,6 +1112,8 @@ int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb, int hdr_len
l2tp_skb_set_owner_w(skb, sk);
l2tp_xmit_core(session, skb, data_len);
+out_unlock:
+ bh_unlock_sock(sk);
abort:
return 0;
--
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