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authorEric Dumazet <edumazet@google.com>2012-12-21 07:32:10 +0000
committerDavid S. Miller <davem@davemloft.net>2012-12-21 13:14:07 -0800
commit9650388b5c56578fdccc79c57a8c82fb92b8e7f1 (patch)
tree059e144f4318f5690bac0ff7b294028408094e69
parent9fdc6bef5f1e8b5d3e65c2e7086033034b0dd307 (diff)
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>
-rw-r--r--net/ipv4/arp.c8
1 files changed, 3 insertions, 5 deletions
diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index ce6fbdfd40b8..1169ed41d587 100644
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -321,7 +321,7 @@ static void arp_error_report(struct neighbour *neigh, struct sk_buff *skb)
static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb)
{
__be32 saddr = 0;
- u8 *dst_ha = NULL;
+ u8 dst_ha[MAX_ADDR_LEN];
struct net_device *dev = neigh->dev;
__be32 target = *(__be32 *)neigh->primary_key;
int probes = atomic_read(&neigh->probes);
@@ -363,9 +363,9 @@ static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb)
if (probes < 0) {
if (!(neigh->nud_state & NUD_VALID))
pr_debug("trying to ucast probe in NUD_INVALID\n");
- dst_ha = neigh->ha;
- read_lock_bh(&neigh->lock);
+ neigh_ha_snapshot(dst_ha, neigh, dev);
} else {
+ memset(dst_ha, 0, dev->addr_len);
probes -= neigh->parms->app_probes;
if (probes < 0) {
#ifdef CONFIG_ARPD
@@ -377,8 +377,6 @@ static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb)
arp_send(ARPOP_REQUEST, ETH_P_ARP, target, dev, saddr,
dst_ha, dev->dev_addr, NULL);
- if (dst_ha)
- read_unlock_bh(&neigh->lock);
}
static int arp_ignore(struct in_device *in_dev, __be32 sip, __be32 tip)