net: Fix RCU splat in af_key

commit ba51b6be upstream.

Hit the following splat testing VRF change for ipsec:

[  113.475692] ===============================
[  113.476194] [ INFO: suspicious RCU usage. ]
[  113.476667] 4.2.0-rc6-1+deb7u2+clUNRELEASED #3.2.65-1+deb7u2+clUNRELEASED Not tainted
[  113.477545] -------------------------------
[  113.478013] /work/monster-14/dsa/kernel.git/include/linux/rcupdate.h:568 Illegal context switch in RCU read-side critical section!
[  113.479288]
[  113.479288] other info that might help us debug this:
[  113.479288]
[  113.480207]
[  113.480207] rcu_scheduler_active = 1, debug_locks = 1
[  113.480931] 2 locks held by setkey/6829:
[  113.481371]  #0:  (&net->xfrm.xfrm_cfg_mutex){+.+.+.}, at: [<ffffffff814e9887>] pfkey_sendmsg+0xfb/0x213
[  113.482509]  #1:  (rcu_read_lock){......}, at: [<ffffffff814e767f>] rcu_read_lock+0x0/0x6e
[  113.483509]
[  113.483509] stack backtrace:
[  113.484041] CPU: 0 PID: 6829 Comm: setkey Not tainted 4.2.0-rc6-1+deb7u2+clUNRELEASED #3.2.65-1+deb7u2+clUNRELEASED
[  113.485422] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.7.5.1-0-g8936dbb-20141113_115728-nilsson.home.kraxel.org 04/01/2014
[  113.486845]  0000000000000001 ffff88001d4c7a98 ffffffff81518af2 ffffffff81086962
[  113.487732]  ffff88001d538480 ffff88001d4c7ac8 ffffffff8107ae75 ffffffff8180a154
[  113.488628]  0000000000000b30 0000000000000000 00000000000000d0 ffff88001d4c7ad8
[  113.489525] Call Trace:
[  113.489813]  [<ffffffff81518af2>] dump_stack+0x4c/0x65
[  113.490389]  [<ffffffff81086962>] ? console_unlock+0x3d6/0x405
[  113.491039]  [<ffffffff8107ae75>] lockdep_rcu_suspicious+0xfa/0x103
[  113.491735]  [<ffffffff81064032>] rcu_preempt_sleep_check+0x45/0x47
[  113.492442]  [<ffffffff8106404d>] ___might_sleep+0x19/0x1c8
[  113.493077]  [<ffffffff81064268>] __might_sleep+0x6c/0x82
[  113.493681]  [<ffffffff81133190>] cache_alloc_debugcheck_before.isra.50+0x1d/0x24
[  113.494508]  [<ffffffff81134876>] kmem_cache_alloc+0x31/0x18f
[  113.495149]  [<ffffffff814012b5>] skb_clone+0x64/0x80
[  113.495712]  [<ffffffff814e6f71>] pfkey_broadcast_one+0x3d/0xff
[  113.496380]  [<ffffffff814e7b84>] pfkey_broadcast+0xb5/0x11e
[  113.497024]  [<ffffffff814e82d1>] pfkey_register+0x191/0x1b1
[  113.497653]  [<ffffffff814e9770>] pfkey_process+0x162/0x17e
[  113.498274]  [<ffffffff814e9895>] pfkey_sendmsg+0x109/0x213

In pfkey_sendmsg the net mutex is taken and then pfkey_broadcast takes
the RCU lock.

Since pfkey_broadcast takes the RCU lock the allocation argument is
pointless since GFP_ATOMIC must be used between the rcu_read_{,un}lock.
The one call outside of rcu can be done with GFP_KERNEL.

Fixes: 7f6b9dbd ("af_key: locking change")
Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

net/key/af_key.c

@@ -220,7 +220,7 @@ static int pfkey_broadcast_one(struct sk_buff *skb, struct sk_buff **skb2,
 #define BROADCAST_ONE		1
 #define BROADCAST_REGISTERED	2
 #define BROADCAST_PROMISC_ONLY	4
-static int pfkey_broadcast(struct sk_buff *skb, gfp_t allocation,
+static int pfkey_broadcast(struct sk_buff *skb,
 			   int broadcast_flags, struct sock *one_sk,
 			   struct net *net)
 {
@@ -246,7 +246,7 @@ static int pfkey_broadcast(struct sk_buff *skb, gfp_t allocation,
 		 * socket.
 		 */
 		if (pfk->promisc)
-			pfkey_broadcast_one(skb, &skb2, allocation, sk);
+			pfkey_broadcast_one(skb, &skb2, GFP_ATOMIC, sk);
 
 		/* the exact target will be processed later */
 		if (sk == one_sk)
@@ -261,7 +261,7 @@ static int pfkey_broadcast(struct sk_buff *skb, gfp_t allocation,
 				continue;
 		}
 
-		err2 = pfkey_broadcast_one(skb, &skb2, allocation, sk);
+		err2 = pfkey_broadcast_one(skb, &skb2, GFP_ATOMIC, sk);
 
 		/* Error is cleare after succecful sending to at least one
 		 * registered KM */
@@ -271,7 +271,7 @@ static int pfkey_broadcast(struct sk_buff *skb, gfp_t allocation,
 	rcu_read_unlock();
 
 	if (one_sk != NULL)
-		err = pfkey_broadcast_one(skb, &skb2, allocation, one_sk);
+		err = pfkey_broadcast_one(skb, &skb2, GFP_KERNEL, one_sk);
 
 	kfree_skb(skb2);
 	kfree_skb(skb);
@@ -294,7 +294,7 @@ static int pfkey_do_dump(struct pfkey_sock *pfk)
 		hdr = (struct sadb_msg *) pfk->dump.skb->data;
 		hdr->sadb_msg_seq = 0;
 		hdr->sadb_msg_errno = rc;
-		pfkey_broadcast(pfk->dump.skb, GFP_ATOMIC, BROADCAST_ONE,
+		pfkey_broadcast(pfk->dump.skb, BROADCAST_ONE,
 				&pfk->sk, sock_net(&pfk->sk));
 		pfk->dump.skb = NULL;
 	}
@@ -335,7 +335,7 @@ static int pfkey_error(const struct sadb_msg *orig, int err, struct sock *sk)
 	hdr->sadb_msg_len = (sizeof(struct sadb_msg) /
 			     sizeof(uint64_t));
 
-	pfkey_broadcast(skb, GFP_KERNEL, BROADCAST_ONE, sk, sock_net(sk));
+	pfkey_broadcast(skb, BROADCAST_ONE, sk, sock_net(sk));
 
 	return 0;
 }
@@ -1361,7 +1361,7 @@ static int pfkey_getspi(struct sock *sk, struct sk_buff *skb, const struct sadb_
 
 	xfrm_state_put(x);
 
-	pfkey_broadcast(resp_skb, GFP_KERNEL, BROADCAST_ONE, sk, net);
+	pfkey_broadcast(resp_skb, BROADCAST_ONE, sk, net);
 
 	return 0;
 }
@@ -1449,7 +1449,7 @@ static int key_notify_sa(struct xfrm_state *x, const struct km_event *c)
 	hdr->sadb_msg_seq = c->seq;
 	hdr->sadb_msg_pid = c->pid;
 
-	pfkey_broadcast(skb, GFP_ATOMIC, BROADCAST_ALL, NULL, xs_net(x));
+	pfkey_broadcast(skb, BROADCAST_ALL, NULL, xs_net(x));
 
 	return 0;
 }
@@ -1566,7 +1566,7 @@ static int pfkey_get(struct sock *sk, struct sk_buff *skb, const struct sadb_msg
 	out_hdr->sadb_msg_reserved = 0;
 	out_hdr->sadb_msg_seq = hdr->sadb_msg_seq;
 	out_hdr->sadb_msg_pid = hdr->sadb_msg_pid;
-	pfkey_broadcast(out_skb, GFP_ATOMIC, BROADCAST_ONE, sk, sock_net(sk));
+	pfkey_broadcast(out_skb, BROADCAST_ONE, sk, sock_net(sk));
 
 	return 0;
 }
@@ -1667,7 +1667,7 @@ static int pfkey_register(struct sock *sk, struct sk_buff *skb, const struct sad
 		return -ENOBUFS;
 	}
 
-	pfkey_broadcast(supp_skb, GFP_KERNEL, BROADCAST_REGISTERED, sk, sock_net(sk));
+	pfkey_broadcast(supp_skb, BROADCAST_REGISTERED, sk, sock_net(sk));
 
 	return 0;
 }
@@ -1686,7 +1686,7 @@ static int unicast_flush_resp(struct sock *sk, const struct sadb_msg *ihdr)
 	hdr->sadb_msg_errno = (uint8_t) 0;
 	hdr->sadb_msg_len = (sizeof(struct sadb_msg) / sizeof(uint64_t));
 
-	return pfkey_broadcast(skb, GFP_ATOMIC, BROADCAST_ONE, sk, sock_net(sk));
+	return pfkey_broadcast(skb, BROADCAST_ONE, sk, sock_net(sk));
 }
 
 static int key_notify_sa_flush(const struct km_event *c)
@@ -1707,7 +1707,7 @@ static int key_notify_sa_flush(const struct km_event *c)
 	hdr->sadb_msg_len = (sizeof(struct sadb_msg) / sizeof(uint64_t));
 	hdr->sadb_msg_reserved = 0;
 
-	pfkey_broadcast(skb, GFP_ATOMIC, BROADCAST_ALL, NULL, c->net);
+	pfkey_broadcast(skb, BROADCAST_ALL, NULL, c->net);
 
 	return 0;
 }
@@ -1768,7 +1768,7 @@ static int dump_sa(struct xfrm_state *x, int count, void *ptr)
 	out_hdr->sadb_msg_pid = pfk->dump.msg_pid;
 
 	if (pfk->dump.skb)
-		pfkey_broadcast(pfk->dump.skb, GFP_ATOMIC, BROADCAST_ONE,
+		pfkey_broadcast(pfk->dump.skb, BROADCAST_ONE,
 				&pfk->sk, sock_net(&pfk->sk));
 	pfk->dump.skb = out_skb;
 
@@ -1829,7 +1829,7 @@ static int pfkey_promisc(struct sock *sk, struct sk_buff *skb, const struct sadb
 		new_hdr->sadb_msg_errno = 0;
 	}
 
-	pfkey_broadcast(skb, GFP_KERNEL, BROADCAST_ALL, NULL, sock_net(sk));
+	pfkey_broadcast(skb, BROADCAST_ALL, NULL, sock_net(sk));
 	return 0;
 }
 
@@ -2160,7 +2160,7 @@ static int key_notify_policy(struct xfrm_policy *xp, int dir, const struct km_ev
 	out_hdr->sadb_msg_errno = 0;
 	out_hdr->sadb_msg_seq = c->seq;
 	out_hdr->sadb_msg_pid = c->pid;
-	pfkey_broadcast(out_skb, GFP_ATOMIC, BROADCAST_ALL, NULL, xp_net(xp));
+	pfkey_broadcast(out_skb, BROADCAST_ALL, NULL, xp_net(xp));
 	return 0;
 
 }
@@ -2386,7 +2386,7 @@ static int key_pol_get_resp(struct sock *sk, struct xfrm_policy *xp, const struc
 	out_hdr->sadb_msg_errno = 0;
 	out_hdr->sadb_msg_seq = hdr->sadb_msg_seq;
 	out_hdr->sadb_msg_pid = hdr->sadb_msg_pid;
-	pfkey_broadcast(out_skb, GFP_ATOMIC, BROADCAST_ONE, sk, xp_net(xp));
+	pfkey_broadcast(out_skb, BROADCAST_ONE, sk, xp_net(xp));
 	err = 0;
 
 out:
@@ -2639,7 +2639,7 @@ static int dump_sp(struct xfrm_policy *xp, int dir, int count, void *ptr)
 	out_hdr->sadb_msg_pid = pfk->dump.msg_pid;
 
 	if (pfk->dump.skb)
-		pfkey_broadcast(pfk->dump.skb, GFP_ATOMIC, BROADCAST_ONE,
+		pfkey_broadcast(pfk->dump.skb, BROADCAST_ONE,
 				&pfk->sk, sock_net(&pfk->sk));
 	pfk->dump.skb = out_skb;
 
@@ -2690,7 +2690,7 @@ static int key_notify_policy_flush(const struct km_event *c)
 	hdr->sadb_msg_satype = SADB_SATYPE_UNSPEC;
 	hdr->sadb_msg_len = (sizeof(struct sadb_msg) / sizeof(uint64_t));
 	hdr->sadb_msg_reserved = 0;
-	pfkey_broadcast(skb_out, GFP_ATOMIC, BROADCAST_ALL, NULL, c->net);
+	pfkey_broadcast(skb_out, BROADCAST_ALL, NULL, c->net);
 	return 0;
 
 }
@@ -2756,7 +2756,7 @@ static int pfkey_process(struct sock *sk, struct sk_buff *skb, const struct sadb
 	void *ext_hdrs[SADB_EXT_MAX];
 	int err;
 
-	pfkey_broadcast(skb_clone(skb, GFP_KERNEL), GFP_KERNEL,
+	pfkey_broadcast(skb_clone(skb, GFP_KERNEL),
 			BROADCAST_PROMISC_ONLY, NULL, sock_net(sk));
 
 	memset(ext_hdrs, 0, sizeof(ext_hdrs));
@@ -2962,7 +2962,7 @@ static int key_notify_sa_expire(struct xfrm_state *x, const struct km_event *c)
 	out_hdr->sadb_msg_seq = 0;
 	out_hdr->sadb_msg_pid = 0;
 
-	pfkey_broadcast(out_skb, GFP_ATOMIC, BROADCAST_REGISTERED, NULL, xs_net(x));
+	pfkey_broadcast(out_skb, BROADCAST_REGISTERED, NULL, xs_net(x));
 	return 0;
 }
 
@@ -3134,7 +3134,7 @@ static int pfkey_send_acquire(struct xfrm_state *x, struct xfrm_tmpl *t, struct
 		       xfrm_ctx->ctx_len);
 	}
 
-	return pfkey_broadcast(skb, GFP_ATOMIC, BROADCAST_REGISTERED, NULL, xs_net(x));
+	return pfkey_broadcast(skb, BROADCAST_REGISTERED, NULL, xs_net(x));
 }
 
 static struct xfrm_policy *pfkey_compile_policy(struct sock *sk, int opt,
@@ -3332,7 +3332,7 @@ static int pfkey_send_new_mapping(struct xfrm_state *x, xfrm_address_t *ipaddr,
 	n_port->sadb_x_nat_t_port_port = sport;
 	n_port->sadb_x_nat_t_port_reserved = 0;
 
-	return pfkey_broadcast(skb, GFP_ATOMIC, BROADCAST_REGISTERED, NULL, xs_net(x));
+	return pfkey_broadcast(skb, BROADCAST_REGISTERED, NULL, xs_net(x));
 }
 
 #ifdef CONFIG_NET_KEY_MIGRATE
@@ -3524,7 +3524,7 @@ static int pfkey_send_migrate(const struct xfrm_selector *sel, u8 dir, u8 type,
 	}
 
 	/* broadcast migrate message to sockets */
-	pfkey_broadcast(skb, GFP_ATOMIC, BROADCAST_ALL, NULL, &init_net);
+	pfkey_broadcast(skb, BROADCAST_ALL, NULL, &init_net);
 
 	return 0;