From: Florian Westphal <fw@strlen.de>
Date: Thu, 27 Jun 2019 12:03:32 +0000 (+0200)
Subject: net: ipv4: fix infinite loop on secondary addr promotion
X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=6a9e9cea4c51dd7137f381710bb42e2ad6e7e285;p=openwrt%2Fstaging%2Fblogic.git

net: ipv4: fix infinite loop on secondary addr promotion

secondary address promotion causes infinite loop -- it arranges
for ifa->ifa_next to point back to itself.

Problem is that 'prev_prom' and 'last_prim' might point at the same entry,
so 'last_sec' pointer must be obtained after prev_prom->next update.

Fixes: 2638eb8b50cf ("net: ipv4: provide __rcu annotation for ifa_list")
Reported-by: Ran Rozenstein <ranro@mellanox.com>
Reported-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 7874303220c5..137d1892395d 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -428,8 +428,9 @@ no_promotions:
 		if (prev_prom) {
 			struct in_ifaddr *last_sec;
 
-			last_sec = rtnl_dereference(last_prim->ifa_next);
 			rcu_assign_pointer(prev_prom->ifa_next, next_sec);
+
+			last_sec = rtnl_dereference(last_prim->ifa_next);
 			rcu_assign_pointer(promote->ifa_next, last_sec);
 			rcu_assign_pointer(last_prim->ifa_next, promote);
 		}