icmp: icmp_sk() should not use smp_processor_id() in preemptible code

Pass namespace into icmp_xmit_lock, obtain socket inside and return
it as a result for caller.

Thanks Alexey Dobryan for this report:

Steps to reproduce:

CONFIG_PREEMPT=y
CONFIG_DEBUG_PREEMPT=y
tracepath <something>

BUG: using smp_processor_id() in preemptible [00000000] code: tracepath/3205
caller is icmp_sk+0x15/0x30
Pid: 3205, comm: tracepath Not tainted 2.6.27-rc4 #1

Call Trace:
[<ffffffff8031af14>] debug_smp_processor_id+0xe4/0xf0
[<ffffffff80409405>] icmp_sk+0x15/0x30
[<ffffffff8040a17b>] icmp_send+0x4b/0x3f0
[<ffffffff8025a415>] ? trace_hardirqs_on_caller+0xd5/0x160
[<ffffffff8025a4ad>] ? trace_hardirqs_on+0xd/0x10
[<ffffffff8023a475>] ? local_bh_enable_ip+0x95/0x110
[<ffffffff804285b9>] ? _spin_unlock_bh+0x39/0x40
[<ffffffff8025a26c>] ? mark_held_locks+0x4c/0x90
[<ffffffff8025a4ad>] ? trace_hardirqs_on+0xd/0x10
[<ffffffff8025a415>] ? trace_hardirqs_on_caller+0xd5/0x160
[<ffffffff803e91b4>] ip_fragment+0x8d4/0x900
[<ffffffff803e7030>] ? ip_finish_output2+0x0/0x290
[<ffffffff803e91e0>] ? ip_finish_output+0x0/0x60
[<ffffffff803e6650>] ? dst_output+0x0/0x10
[<ffffffff803e922c>] ip_finish_output+0x4c/0x60
[<ffffffff803e92e3>] ip_output+0xa3/0xf0
[<ffffffff803e68d0>] ip_local_out+0x20/0x30
[<ffffffff803e753f>] ip_push_pending_frames+0x27f/0x400
[<ffffffff80406313>] udp_push_pending_frames+0x233/0x3d0
[<ffffffff804067d1>] udp_sendmsg+0x321/0x6f0
[<ffffffff8040d155>] inet_sendmsg+0x45/0x80
[<ffffffff803b967f>] sock_sendmsg+0xdf/0x110
[<ffffffff8024a100>] ? autoremove_wake_function+0x0/0x40
[<ffffffff80257ce5>] ? validate_chain+0x415/0x1010
[<ffffffff8027dc10>] ? __do_fault+0x140/0x450
[<ffffffff802597d0>] ? __lock_acquire+0x260/0x590
[<ffffffff803b9e55>] ? sockfd_lookup_light+0x45/0x80
[<ffffffff803ba50a>] sys_sendto+0xea/0x120
[<ffffffff80428e42>] ? _spin_unlock_irqrestore+0x42/0x80
[<ffffffff803134bc>] ? __up_read+0x4c/0xb0
[<ffffffff8024e0c6>] ? up_read+0x26/0x30
[<ffffffff8020b8bb>] system_call_fastpath+0x16/0x1b

icmp6_sk() is similar.

Signed-off-by: Denis V. Lunev <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/ipv4/icmp.c

···
 	return net->ipv4.icmp_sk[smp_processor_id()];
 }
 
-static inline int icmp_xmit_lock(struct sock *sk)
+static inline struct sock *icmp_xmit_lock(struct net *net)
 {
+	struct sock *sk;
+
 	local_bh_disable();
+
+	sk = icmp_sk(net);
 
 	if (unlikely(!spin_trylock(&sk->sk_lock.slock))) {
 		/* This can happen if the output path signals a
 		 * dst_link_failure() for an outgoing ICMP packet.
 		 */
 		local_bh_enable();
-		return 1;
+		return NULL;
 	}
-	return 0;
+	return sk;
 }
 
 static inline void icmp_xmit_unlock(struct sock *sk)
···
 	struct ipcm_cookie ipc;
 	struct rtable *rt = skb->rtable;
 	struct net *net = dev_net(rt->u.dst.dev);
-	struct sock *sk = icmp_sk(net);
-	struct inet_sock *inet = inet_sk(sk);
+	struct sock *sk;
+	struct inet_sock *inet;
 	__be32 daddr;
 
 	if (ip_options_echo(&icmp_param->replyopts, skb))
 		return;
 
-	if (icmp_xmit_lock(sk))
+	sk = icmp_xmit_lock(net);
+	if (sk == NULL)
 		return;
+	inet = inet_sk(sk);
 
 	icmp_param->data.icmph.checksum = 0;
 
···
 	if (!rt)
 		goto out;
 	net = dev_net(rt->u.dst.dev);
-	sk = icmp_sk(net);
 
 	/*
 	 *	Find the original header. It is expected to be valid, of course.
···
 		}
 	}
 
-	if (icmp_xmit_lock(sk))
+	sk = icmp_xmit_lock(net);
+	if (sk == NULL)
 		return;
 
 	/*

net/ipv6/icmp.c

···
 	.flags		=	INET6_PROTO_NOPOLICY|INET6_PROTO_FINAL,
 };
 
-static __inline__ int icmpv6_xmit_lock(struct sock *sk)
+static __inline__ struct sock *icmpv6_xmit_lock(struct net *net)
 {
+	struct sock *sk;
+
 	local_bh_disable();
 
+	sk = icmpv6_sk(net);
 	if (unlikely(!spin_trylock(&sk->sk_lock.slock))) {
 		/* This can happen if the output path (f.e. SIT or
 		 * ip6ip6 tunnel) signals dst_link_failure() for an
 		 * outgoing ICMP6 packet.
 		 */
 		local_bh_enable();
-		return 1;
+		return NULL;
 	}
-	return 0;
+	return sk;
 }
 
 static __inline__ void icmpv6_xmit_unlock(struct sock *sk)
···
 	fl.fl_icmp_code = code;
 	security_skb_classify_flow(skb, &fl);
 
-	sk = icmpv6_sk(net);
-	np = inet6_sk(sk);
-
-	if (icmpv6_xmit_lock(sk))
+	sk = icmpv6_xmit_lock(net);
+	if (sk == NULL)
 		return;
+	np = inet6_sk(sk);
 
 	if (!icmpv6_xrlim_allow(sk, type, &fl))
 		goto out;
···
 	fl.fl_icmp_type = ICMPV6_ECHO_REPLY;
 	security_skb_classify_flow(skb, &fl);
 
-	sk = icmpv6_sk(net);
-	np = inet6_sk(sk);
-
-	if (icmpv6_xmit_lock(sk))
+	sk = icmpv6_xmit_lock(net);
+	if (sk == NULL)
 		return;
+	np = inet6_sk(sk);
 
 	if (!fl.oif && ipv6_addr_is_multicast(&fl.fl6_dst))
 		fl.oif = np->mcast_oif;