xfrm: fix rcu lock in xfrm_notify_userpolicy()

As stated in the comment above xfrm_nlmsg_multicast(), rcu read lock must
be held before calling this function.

Reported-by: syzbot+3d9866419b4aa8f985d6@syzkaller.appspotmail.com
Fixes: 703b94b93c19 ("xfrm: notify default policy on update")
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index 0eba0c2..3a3cb09 100644 (file)
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -1967,6 +1967,7 @@ static int xfrm_notify_userpolicy(struct net *net)
        int len = NLMSG_ALIGN(sizeof(*up));
        struct nlmsghdr *nlh;
        struct sk_buff *skb;
+       int err;
 
        skb = nlmsg_new(len, GFP_ATOMIC);
        if (skb == NULL)
@@ -1988,7 +1989,11 @@ static int xfrm_notify_userpolicy(struct net *net)
 
        nlmsg_end(skb, nlh);
 
-       return xfrm_nlmsg_multicast(net, skb, 0, XFRMNLGRP_POLICY);
+       rcu_read_lock();
+       err = xfrm_nlmsg_multicast(net, skb, 0, XFRMNLGRP_POLICY);
+       rcu_read_unlock();
+
+       return err;
 }
 
 static int xfrm_set_default(struct sk_buff *skb, struct nlmsghdr *nlh,