netdev - [PATCH net-next] net: Set tw refcount before dropping the ehash chain lock.

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Message-ID: <20181220205908.1056118-1-jonathan.lemon@gmail.com>
Date:   Thu, 20 Dec 2018 12:59:08 -0800
From:   Jonathan Lemon <jonathan.lemon@...il.com>
To:     <netdev@...r.kernel.org>
CC:     <davem@...emloft.net>, <edumazet@...gle.com>, <kernel-team@...com>,
        Jonathan Lemon <jonathan.lemon@...il.com>
Subject: [PATCH net-next] net: Set tw refcount before dropping the ehash chain lock.

This protects against callers like inet_diag_dump_icsk(), which may walk the
chain on another cpu and change the refcount before the tw structure is ready.

Signed-off-by: Jonathan Lemon <jonathan.lemon@...il.com>
---
 net/ipv4/inet_timewait_sock.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/inet_timewait_sock.c b/net/ipv4/inet_timewait_sock.c
index 88c5069b5d20..128cfcada5e6 100644
--- a/net/ipv4/inet_timewait_sock.c
+++ b/net/ipv4/inet_timewait_sock.c
@@ -125,8 +125,6 @@ void inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk,
 	if (__sk_nulls_del_node_init_rcu(sk))
 		sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
 
-	spin_unlock(lock);
-
 	/* tw_refcnt is set to 3 because we have :
 	 * - one reference for bhash chain.
 	 * - one reference for ehash chain.
@@ -137,6 +135,8 @@ void inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk,
 	 * so we are not allowed to use tw anymore.
 	 */
 	refcount_set(&tw->tw_refcnt, 3);
+
+	spin_unlock(lock);
 }
 EXPORT_SYMBOL_GPL(inet_twsk_hashdance);
 
-- 
2.17.1