[PATCH net] ipv6: flowlabel: fl6_sock_lookup() must use atomic_inc_not_zero

[Eric Dumazet]

RCU 101 : Before taking a refcount, make sure the object is not already
          scheduled for deletion.

Fixes: 18367681a10b ("ipv6 flowlabel: Convert np->ipv6_fl_list to RCU.")
Signed-off-by: Eric Dumazet <eduma...@google.com>
Cc: Willem de Bruijn <will...@google.com>
---
 net/ipv6/ip6_flowlabel.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv6/ip6_flowlabel.c b/net/ipv6/ip6_flowlabel.c
index 
be5f3d7ceb966d609121f89a6cc5dcc605834c89..31dec1f00ad267b66449a42ab989236e9f7af5d9
 100644
--- a/net/ipv6/ip6_flowlabel.c
+++ b/net/ipv6/ip6_flowlabel.c
@@ -254,9 +254,9 @@ struct ip6_flowlabel *fl6_sock_lookup(struct sock *sk, 
__be32 label)
        rcu_read_lock_bh();
        for_each_sk_fl_rcu(np, sfl) {
                struct ip6_flowlabel *fl = sfl->fl;
-               if (fl->label == label) {
+
+               if (fl->label == label && atomic_inc_not_zero(&fl->users)) {
                        fl->lastuse = jiffies;
-                       atomic_inc(&fl->users);
                        rcu_read_unlock_bh();
                        return fl;
                }
-- 
2.22.0.rc1.311.g5d7573a151-goog