tcp: fix listening_get_next()

Alexey Vlasov found /proc/net/tcp could sometime loop and display
millions of sockets in LISTEN state.

In 2.6.29, when we converted TCP hash tables to RCU, we left two
sk_next() calls in listening_get_next().

We must instead use sk_nulls_next() to properly detect an end of chain.

Reported-by: Alexey Vlasov <renton@renton.name>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 2 deletions

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index e13da6de1fc7..d978bb2f748b 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2030,7 +2030,7 @@ static void *listening_get_next(struct seq_file *seq, void *cur)
 get_req:
                         req = icsk->icsk_accept_queue.listen_opt->syn_table[st->sbucket];
                 }
-                sk        = sk_next(st->syn_wait_sk);
+                sk        = sk_nulls_next(st->syn_wait_sk);
                 st->state = TCP_SEQ_STATE_LISTENING;
                 read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
         } else {
@@ -2039,7 +2039,7 @@ get_req:
                 if (reqsk_queue_len(&icsk->icsk_accept_queue))
                         goto start_req;
                 read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
-                sk = sk_next(sk);
+                sk = sk_nulls_next(sk);
         }
 get_sk:
         sk_nulls_for_each_from(sk, node) {