Commit a2d6cbb0 authored Apr 10, 2017 by Rabin Vincent Committed by David S. Miller Apr 12, 2017

ipv6: Fix idev->addr_list corruption



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: 6a923934 (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>

parent df7dd8fc

net/ipv6/addrconf.c

+7 −4

Original line number	Diff line number	Diff line
		@@ -3626,14 +3626,19 @@ restart:
		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 @@ restart:
		} else {
		state = ifa->state;
		ifa->state = INET6_IFADDR_STATE_DEAD;

		list_move(&ifa->if_list, &del_list);
		}

		spin_unlock_bh(&ifa->lock);

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