netdev - [PATCH net-next] tcp/dccp: fix inet_reuseport_add

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Date:	Wed, 06 Apr 2016 22:07:34 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Ahern <dsa@...ulusnetworks.com>,
	David Miller <davem@...emloft.net>
Cc:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	edumazet@...gle.com
Subject: [PATCH net-next] tcp/dccp: fix inet_reuseport_add_sock()

From: Eric Dumazet <edumazet@...gle.com>

David Ahern reported panics in __inet_hash() caused by my recent commit.

The reason is inet_reuseport_add_sock() was still using
sk_nulls_for_each_rcu() instead of sk_for_each_rcu().
SO_REUSEPORT enabled listeners were causing an instant crash.

While chasing this bug, I found that I forgot to clear SOCK_RCU_FREE
flag, as it is inherited from the parent at clone time.

Fixes: 3b24d854cb35 ("tcp/dccp: do not touch listener sk_refcnt under synflood")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Reported-by: David Ahern <dsa@...ulusnetworks.com>
---
 net/ipv4/inet_connection_sock.c |    3 +++
 net/ipv4/inet_hashtables.c      |    3 +--
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index bc5196ea1bdf..ab69da2d2a77 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -661,6 +661,9 @@ struct sock *inet_csk_clone_lock(const struct sock *sk,
 		inet_sk(newsk)->inet_sport = htons(inet_rsk(req)->ir_num);
 		newsk->sk_write_space = sk_stream_write_space;
 
+		/* listeners have SOCK_RCU_FREE, not the children */
+		sock_reset_flag(newsk, SOCK_RCU_FREE);
+
 		newsk->sk_mark = inet_rsk(req)->ir_mark;
 		atomic64_set(&newsk->sk_cookie,
 			     atomic64_read(&inet_rsk(req)->ir_cookie));
diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index 98ba03b6f87d..fcadb670f50b 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -439,10 +439,9 @@ static int inet_reuseport_add_sock(struct sock *sk,
 						     bool match_wildcard))
 {
 	struct sock *sk2;
-	struct hlist_nulls_node *node;
 	kuid_t uid = sock_i_uid(sk);
 
-	sk_nulls_for_each_rcu(sk2, node, &ilb->head) {
+	sk_for_each_rcu(sk2, &ilb->head) {
 		if (sk2 != sk &&
 		    sk2->sk_family == sk->sk_family &&
 		    ipv6_only_sock(sk2) == ipv6_only_sock(sk) &&