[PATCH 4.2 09/54] inet: fix races in reqsk_queue_hash_req()

Greg Kroah-Hartman
2015-10-23T17:47:03Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 29c6852602e259d2c1882f320b29d5c3fec0de04 ]

Before allowing lockless LISTEN processing, we need to make
sure to arm the SYN_RECV timer before the req socket is visible
in hash tables.

Also, req->rsk_hash should be written before we set rsk_refcnt
to a non zero value.

Fixes: fa76ce7328b2 ("inet: get rid of central tcp/dccp listener timer")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Ying Cai <ycai@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv4/inet_connection_sock.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -685,20 +685,20 @@ void reqsk_queue_hash_req(struct request
req->num_timeout = 0;
req->sk = NULL;

+ setup_timer(&req->rsk_timer, reqsk_timer_handler, (unsigned long)req);
+ mod_timer_pinned(&req->rsk_timer, jiffies + timeout);
+ req->rsk_hash = hash;
+
/* before letting lookups find us, make sure all req fields
* are committed to memory and refcnt initialized.
*/
smp_wmb();
atomic_set(&req->rsk_refcnt, 2);
- setup_timer(&req->rsk_timer, reqsk_timer_handler, (unsigned long)req);
- req->rsk_hash = hash;

spin_lock(&queue->syn_wait_lock);
req->dl_next = lopt->syn_table[hash];
lopt->syn_table[hash] = req;
spin_unlock(&queue->syn_wait_lock);
-
- mod_timer_pinned(&req->rsk_timer, jiffies + timeout);
}
EXPORT_SYMBOL(reqsk_queue_hash_req);