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ipv6: Fix idev->addr_list corruption

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addrconf_ifdown() removes elements from the idev->addr_list without
holding the idev->lock.

If this happens while the loop in __ipv6_dev_get_saddr() is handling the
same element, that function ends up in an infinite loop:

  NMI watchdog: BUG: soft lockup - CPU#1 stuck for 23s! [test:1719]
  Call Trace:
   ipv6_get_saddr_eval+0x13c/0x3a0
   __ipv6_dev_get_saddr+0xe4/0x1f0
   ipv6_dev_get_saddr+0x1b4/0x204
   ip6_dst_lookup_tail+0xcc/0x27c
   ip6_dst_lookup_flow+0x38/0x80
   udpv6_sendmsg+0x708/0xba8
   sock_sendmsg+0x18/0x30
   SyS_sendto+0xb8/0xf8
   syscall_common+0x34/0x58

Fixes: 6a923934c3 (Revert "ipv6: Revert optional address flusing on ifdown.")
Signed-off-by: Rabin Vincent <rabinv@axis.com>
Acked-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Rabin Vincent 2017-04-10 08:36:39 +02:00 committed by David S. Miller
parent df7dd8fc96
commit a2d6cbb067
1 changed files with 7 additions and 4 deletions
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11
net/ipv6/addrconf.c
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@ -3626,14 +3626,19 @@ static int addrconf_ifdown(struct net_device *dev, int how)
INIT_LIST_HEAD(&del_list);
list_for_each_entry_safe(ifa, tmp, &idev->addr_list, if_list) {
struct rt6_info *rt = NULL;
bool keep;
addrconf_del_dad_work(ifa);
keep = keep_addr && (ifa->flags & IFA_F_PERMANENT) &&
!addr_is_local(&ifa->addr);
if (!keep)
list_move(&ifa->if_list, &del_list);
write_unlock_bh(&idev->lock);
spin_lock_bh(&ifa->lock);
if (keep_addr && (ifa->flags & IFA_F_PERMANENT) &&
!addr_is_local(&ifa->addr)) {
if (keep) {
/* set state to skip the notifier below */
state = INET6_IFADDR_STATE_DEAD;
ifa->state = 0;
@ -3645,8 +3650,6 @@ static int addrconf_ifdown(struct net_device *dev, int how)
} else {
state = ifa->state;
ifa->state = INET6_IFADDR_STATE_DEAD;
list_move(&ifa->if_list, &del_list);
}
spin_unlock_bh(&ifa->lock);