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

[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 <edumazet@google.com>
Cc: Willem de Bruijn <willemb@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

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

[Eric Dumazet]

On Thu, Jun 6, 2019 at 2:22 PM Eric Dumazet <edumazet@google.com> wrote:
>
> RCU 101 : Before taking a refcount, make sure the object is not already
>           scheduled for deletion.
>

I will send a V2, there is a second atomic_inc() which needs to be
changed in ipv6_flowlabel_opt()