Patch "ipv6: Fix idev->addr_list corruption" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

    ipv6: Fix idev->addr_list corruption

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
ipv6-fix-idev-addr_list-corruption.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Rabin Vincent <[email protected]>
Date: Mon, 10 Apr 2017 08:36:39 +0200
Subject: ipv6: Fix idev->addr_list corruption

From: Rabin Vincent <[email protected]>

[ Upstream commit a2d6cbb0670d54806f18192cb0db266b4a6d285a ]

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

---
 net/ipv6/addrconf.c |   11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

@@ -3602,14 +3602,19 @@ 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;

@@ -3621,8 +3626,6 @@ restart:
 		} else {
 			state = ifa->state;
 			ifa->state = INET6_IFADDR_STATE_DEAD;
-
-			list_move(&ifa->if_list, &del_list);
 		}
 
 		spin_unlock_bh(&ifa->lock);

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/ipv6-fix-idev-addr_list-corruption.patch