[PATCH net 1/2] ipv6: route: enforce RCU protection in rt6_update_exception_stamp_rt()

[Paolo Abeni]

We must access rt6_info->from under RCU read lock: move the
dereference under such lock, with proper annotation, and use
rcu_access_pointer() to check for null value outside the lock.

Fixes: a68886a69180 ("net/ipv6: Make from in rt6_info rcu protected")
Signed-off-by: Paolo Abeni <pab...@redhat.com>
---
 net/ipv6/route.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index bd09abd1fb22..cbaa8745d9ff 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1610,15 +1610,15 @@ static int rt6_remove_exception_rt(struct rt6_info *rt)
 static void rt6_update_exception_stamp_rt(struct rt6_info *rt)
 {
        struct rt6_exception_bucket *bucket;
-       struct fib6_info *from = rt->from;
        struct in6_addr *src_key = NULL;
        struct rt6_exception *rt6_ex;
+       struct fib6_info *from;
 
-       if (!from ||
-           !(rt->rt6i_flags & RTF_CACHE))
+       if (!rcu_access_pointer(rt->from) || !(rt->rt6i_flags & RTF_CACHE))
                return;
 
        rcu_read_lock();
+       from = rcu_dereference(rt->from);
        bucket = rcu_dereference(from->rt6i_exception_bucket);
 
 #ifdef CONFIG_IPV6_SUBTREES
-- 
2.20.1