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Eric Dumazet 9650388b5c ipv4: arp: fix a lockdep splat in arp_solicit() 
Yan Burman reported following lockdep warning :

=============================================
[ INFO: possible recursive locking detected ]
3.7.0+ #24 Not tainted
---------------------------------------------
swapper/1/0 is trying to acquire lock:
  (&n->lock){++--..}, at: [<ffffffff8139f56e>] __neigh_event_send
+0x2e/0x2f0

but task is already holding lock:
  (&n->lock){++--..}, at: [<ffffffff813f63f4>] arp_solicit+0x1d4/0x280

other info that might help us debug this:
  Possible unsafe locking scenario:

        CPU0
        ----
   lock(&n->lock);
   lock(&n->lock);

  *** DEADLOCK ***

  May be due to missing lock nesting notation

4 locks held by swapper/1/0:
  #0:  (((&n->timer))){+.-...}, at: [<ffffffff8104b350>]
call_timer_fn+0x0/0x1c0
  #1:  (&n->lock){++--..}, at: [<ffffffff813f63f4>] arp_solicit
+0x1d4/0x280
  #2:  (rcu_read_lock_bh){.+....}, at: [<ffffffff81395400>]
dev_queue_xmit+0x0/0x5d0
  #3:  (rcu_read_lock_bh){.+....}, at: [<ffffffff813cb41e>]
ip_finish_output+0x13e/0x640

stack backtrace:
Pid: 0, comm: swapper/1 Not tainted 3.7.0+ #24
Call Trace:
  <IRQ>  [<ffffffff8108c7ac>] validate_chain+0xdcc/0x11f0
  [<ffffffff8108d570>] ? __lock_acquire+0x440/0xc30
  [<ffffffff81120565>] ? kmem_cache_free+0xe5/0x1c0
  [<ffffffff8108d570>] __lock_acquire+0x440/0xc30
  [<ffffffff813c3570>] ? inet_getpeer+0x40/0x600
  [<ffffffff8108d570>] ? __lock_acquire+0x440/0xc30
  [<ffffffff8139f56e>] ? __neigh_event_send+0x2e/0x2f0
  [<ffffffff8108ddf5>] lock_acquire+0x95/0x140
  [<ffffffff8139f56e>] ? __neigh_event_send+0x2e/0x2f0
  [<ffffffff8108d570>] ? __lock_acquire+0x440/0xc30
  [<ffffffff81448d4b>] _raw_write_lock_bh+0x3b/0x50
  [<ffffffff8139f56e>] ? __neigh_event_send+0x2e/0x2f0
  [<ffffffff8139f56e>] __neigh_event_send+0x2e/0x2f0
  [<ffffffff8139f99b>] neigh_resolve_output+0x16b/0x270
  [<ffffffff813cb62d>] ip_finish_output+0x34d/0x640
  [<ffffffff813cb41e>] ? ip_finish_output+0x13e/0x640
  [<ffffffffa046f146>] ? vxlan_xmit+0x556/0xbec [vxlan]
  [<ffffffff813cb9a0>] ip_output+0x80/0xf0
  [<ffffffff813ca368>] ip_local_out+0x28/0x80
  [<ffffffffa046f25a>] vxlan_xmit+0x66a/0xbec [vxlan]
  [<ffffffffa046f146>] ? vxlan_xmit+0x556/0xbec [vxlan]
  [<ffffffff81394a50>] ? skb_gso_segment+0x2b0/0x2b0
  [<ffffffff81449355>] ? _raw_spin_unlock_irqrestore+0x65/0x80
  [<ffffffff81394c57>] ? dev_queue_xmit_nit+0x207/0x270
  [<ffffffff813950c8>] dev_hard_start_xmit+0x298/0x5d0
  [<ffffffff813956f3>] dev_queue_xmit+0x2f3/0x5d0
  [<ffffffff81395400>] ? dev_hard_start_xmit+0x5d0/0x5d0
  [<ffffffff813f5788>] arp_xmit+0x58/0x60
  [<ffffffff813f59db>] arp_send+0x3b/0x40
  [<ffffffff813f6424>] arp_solicit+0x204/0x280
  [<ffffffff813a1a70>] ? neigh_add+0x310/0x310
  [<ffffffff8139f515>] neigh_probe+0x45/0x70
  [<ffffffff813a1c10>] neigh_timer_handler+0x1a0/0x2a0
  [<ffffffff8104b3cf>] call_timer_fn+0x7f/0x1c0
  [<ffffffff8104b350>] ? detach_if_pending+0x120/0x120
  [<ffffffff8104b748>] run_timer_softirq+0x238/0x2b0
  [<ffffffff813a1a70>] ? neigh_add+0x310/0x310
  [<ffffffff81043e51>] __do_softirq+0x101/0x280
  [<ffffffff814518cc>] call_softirq+0x1c/0x30
  [<ffffffff81003b65>] do_softirq+0x85/0xc0
  [<ffffffff81043a7e>] irq_exit+0x9e/0xc0
  [<ffffffff810264f8>] smp_apic_timer_interrupt+0x68/0xa0
  [<ffffffff8145122f>] apic_timer_interrupt+0x6f/0x80
  <EOI>  [<ffffffff8100a054>] ? mwait_idle+0xa4/0x1c0
  [<ffffffff8100a04b>] ? mwait_idle+0x9b/0x1c0
  [<ffffffff8100a6a9>] cpu_idle+0x89/0xe0
  [<ffffffff81441127>] start_secondary+0x1b2/0x1b6

Bug is from arp_solicit(), releasing the neigh lock after arp_send()
In case of vxlan, we eventually need to write lock a neigh lock later.

Its a false positive, but we can get rid of it without lockdep
annotations.

We can instead use neigh_ha_snapshot() helper.

Reported-by: Yan Burman <yanb@mellanox.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
 		2012-12-21 13:14:07 -08:00
..
9p virtio: 9p: correctly pass physical address to userspace for high pages 2012-10-22 18:19:36 +10:30
802 tokenring: delete all remaining driver support 2012-05-15 20:23:16 -04:00
8021q 8021q: fix vlan device to inherit the unicast filtering capability flag 2012-11-30 12:07:27 -05:00
appletalk userns: Print out socket uids in a user namespace aware fashion. 2012-08-14 21:48:06 -07:00
atm atm: use scnprintf() instead of sprintf() 2012-12-17 20:50:51 -08:00
ax25 userns: Convert net/ax25 to use kuid_t where appropriate 2012-08-14 21:49:42 -07:00
batman-adv batman-adv: use ETH_P_BATMAN 2012-11-30 10:50:22 +01:00
bluetooth Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/hid 2012-12-13 12:00:48 -08:00
bridge bridge: Correctly encode addresses when dumping mdb entries 2012-12-19 12:50:06 -08:00
caif caif_usb: Make the driver name check more efficient 2012-12-09 00:34:02 -05:00
can Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2012-12-13 12:00:02 -08:00
ceph Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client 2012-12-20 14:00:13 -08:00
core net: devnet_rename_seq should be a seqcount 2012-12-21 13:14:01 -08:00
dcb net: Allow DCBnl to use other namespaces besides init_net 2012-12-10 14:09:01 -05:00
dccp inet: Fix kmemleak in tcp_v4/6_syn_recv_sock and dccp_v4/6_request_recv_sock 2012-12-14 13:14:07 -05:00
decnet net: Push capable(CAP_NET_ADMIN) into the rtnl methods 2012-11-18 20:32:44 -05:00
dns_resolver Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2012-12-16 15:40:50 -08:00
dsa dsa: Hide core config options; make drivers select what they need 2012-11-26 17:10:44 -05:00
ethernet ipx: move peII functions 2012-07-19 10:48:00 -07:00
ieee802154 6lowpan: consider checksum bytes in fragmentation threshold 2012-11-30 12:19:24 -05:00
ipv4 ipv4: arp: fix a lockdep splat in arp_solicit() 2012-12-21 13:14:07 -08:00
ipv6 ipv6: addrconf.c: remove unnecessary "if" 2012-12-19 12:50:06 -08:00
ipx userns: Print out socket uids in a user namespace aware fashion. 2012-08-14 21:48:06 -07:00
irda TTY/Serial merge for 3.8-rc1 2012-12-11 14:08:47 -08:00
iucv net: remove skb_orphan_try() 2012-06-15 15:30:15 -07:00
key net: Allow userns root to control llc, netfilter, netlink, packet, and xfrm 2012-11-18 20:32:45 -05:00
l2tp Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2012-11-10 18:32:51 -05:00
lapb lapb: Neaten debugging 2012-05-17 18:45:20 -04:00
llc net: Allow userns root to control llc, netfilter, netlink, packet, and xfrm 2012-11-18 20:32:45 -05:00
mac80211 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2012-12-13 12:00:02 -08:00
mac802154 mac802154: fix destructon ordering for ieee802154 devices 2012-12-14 13:14:07 -05:00
netfilter Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2012-12-13 12:00:02 -08:00
netlabel Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2012-10-02 13:38:27 -07:00
netlink netlink: validate addr_len on bind 2012-12-17 20:50:51 -08:00
netrom net: change return values from -EACCES to -EPERM 2012-09-21 13:58:08 -04:00
nfc nfc: remove noisy message from llcp_sock_sendmsg 2012-12-13 12:58:10 -05:00
openvswitch openvswitch: Use RCU callback when detaching netdevices. 2012-11-28 14:04:34 -08:00
packet net: Allow userns root to control llc, netfilter, netlink, packet, and xfrm 2012-11-18 20:32:45 -05:00
phonet net: Push capable(CAP_NET_ADMIN) into the rtnl methods 2012-11-18 20:32:44 -05:00
rds net: rds: use this_cpu_* per-cpu helper 2012-11-19 18:59:44 -05:00
rfkill Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2012-12-13 12:00:02 -08:00
rose
…
rxrpc Merge branch 'modules-next' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux 2012-10-14 13:39:34 -07:00
sched Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2012-12-12 18:07:07 -08:00
sctp sctp: jsctp_sf_eat_sack: fix jprobes function signature mismatch 2012-12-15 17:14:39 -08:00
sunrpc Merge branch 'for-3.8' of git://linux-nfs.org/~bfields/linux 2012-12-20 14:04:11 -08:00
tipc tipc: refactor accept() code for improved readability 2012-12-07 17:23:24 -05:00
unix net: Don't export sysctls to unprivileged users 2012-11-18 20:30:55 -05:00
wanrouter wanmain: comparing array with NULL 2012-07-24 13:55:21 -07:00
wimax
…
wireless Merge branch 'for-john' of git://git.sipsolutions.net/mac80211-next 2012-12-11 16:04:03 -05:00
x25 net: Fix (nearly-)kernel-doc comments for various functions 2012-07-10 23:13:45 -07:00
xfrm Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/klassert/ipsec-next 2012-11-22 15:25:55 -05:00
Kconfig net: Add INET dependency on aes crypto for the sake of TCP fastopen. 2012-09-04 14:20:14 -04:00
Makefile ipv6: Preserve ipv6 functionality needed by NET 2012-11-18 02:34:00 -05:00
compat.c make get_file() return its argument 2012-09-26 21:10:25 -04:00
nonet.c
…
socket.c cgroup: net_cls: Rework update socket logic 2012-10-26 03:40:51 -04:00
sysctl_net.c user_ns: get rid of duplicate code in net_ctl_permissions 2012-11-18 20:32:45 -05:00