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authorSowmini Varadhan <sowmini.varadhan@oracle.com>2017-03-04 08:57:35 -0800
committerDavid S. Miller <davem@davemloft.net>2017-03-07 14:09:59 -0800
commitb21dd4506b71bdb9c5a20e759255cd2513ea7ebe (patch)
tree47be3cbc15140e37dfe4778a227a7a377390fe90 /net
parent16c09b1c7657522a321b04aa7f4300865b7cb292 (diff)
rds: tcp: Sequence teardown of listen and acceptor sockets to avoid races
Commit a93d01f5777e ("RDS: TCP: avoid bad page reference in rds_tcp_listen_data_ready") added the function rds_tcp_listen_sock_def_readable() to handle the case when a partially set-up acceptor socket drops into rds_tcp_listen_data_ready(). However, if the listen socket (rtn->rds_tcp_listen_sock) is itself going through a tear-down via rds_tcp_listen_stop(), the (*ready)() will be null and we would hit a panic of the form BUG: unable to handle kernel NULL pointer dereference at (null) IP: (null) : ? rds_tcp_listen_data_ready+0x59/0xb0 [rds_tcp] tcp_data_queue+0x39d/0x5b0 tcp_rcv_established+0x2e5/0x660 tcp_v4_do_rcv+0x122/0x220 tcp_v4_rcv+0x8b7/0x980 : In the above case, it is not fatal to encounter a NULL value for ready- we should just drop the packet and let the flush of the acceptor thread finish gracefully. In general, the tear-down sequence for listen() and accept() socket that is ensured by this commit is: rtn->rds_tcp_listen_sock = NULL; /* prevent any new accepts */ In rds_tcp_listen_stop(): serialize with, and prevent, further callbacks using lock_sock() flush rds_wq flush acceptor workq sock_release(listen socket) Signed-off-by: Sowmini Varadhan <sowmini.varadhan@oracle.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/rds/tcp.c15
-rw-r--r--net/rds/tcp.h2
-rw-r--r--net/rds/tcp_listen.c9
3 files changed, 18 insertions, 8 deletions
diff --git a/net/rds/tcp.c b/net/rds/tcp.c
index fbf807a0cc4a..225690076773 100644
--- a/net/rds/tcp.c
+++ b/net/rds/tcp.c
@@ -484,9 +484,10 @@ static void __net_exit rds_tcp_exit_net(struct net *net)
* we do need to clean up the listen socket here.
*/
if (rtn->rds_tcp_listen_sock) {
- rds_tcp_listen_stop(rtn->rds_tcp_listen_sock);
+ struct socket *lsock = rtn->rds_tcp_listen_sock;
+
rtn->rds_tcp_listen_sock = NULL;
- flush_work(&rtn->rds_tcp_accept_w);
+ rds_tcp_listen_stop(lsock, &rtn->rds_tcp_accept_w);
}
}
@@ -523,10 +524,10 @@ static void rds_tcp_kill_sock(struct net *net)
struct rds_tcp_connection *tc, *_tc;
LIST_HEAD(tmp_list);
struct rds_tcp_net *rtn = net_generic(net, rds_tcp_netid);
+ struct socket *lsock = rtn->rds_tcp_listen_sock;
- rds_tcp_listen_stop(rtn->rds_tcp_listen_sock);
rtn->rds_tcp_listen_sock = NULL;
- flush_work(&rtn->rds_tcp_accept_w);
+ rds_tcp_listen_stop(lsock, &rtn->rds_tcp_accept_w);
spin_lock_irq(&rds_tcp_conn_lock);
list_for_each_entry_safe(tc, _tc, &rds_tcp_conn_list, t_tcp_node) {
struct net *c_net = tc->t_cpath->cp_conn->c_net;
@@ -546,8 +547,12 @@ static void rds_tcp_kill_sock(struct net *net)
void *rds_tcp_listen_sock_def_readable(struct net *net)
{
struct rds_tcp_net *rtn = net_generic(net, rds_tcp_netid);
+ struct socket *lsock = rtn->rds_tcp_listen_sock;
+
+ if (!lsock)
+ return NULL;
- return rtn->rds_tcp_listen_sock->sk->sk_user_data;
+ return lsock->sk->sk_user_data;
}
static int rds_tcp_dev_event(struct notifier_block *this,
diff --git a/net/rds/tcp.h b/net/rds/tcp.h
index 9a1cc8906576..56ea6620fcf9 100644
--- a/net/rds/tcp.h
+++ b/net/rds/tcp.h
@@ -66,7 +66,7 @@ void rds_tcp_state_change(struct sock *sk);
/* tcp_listen.c */
struct socket *rds_tcp_listen_init(struct net *);
-void rds_tcp_listen_stop(struct socket *);
+void rds_tcp_listen_stop(struct socket *sock, struct work_struct *acceptor);
void rds_tcp_listen_data_ready(struct sock *sk);
int rds_tcp_accept_one(struct socket *sock);
int rds_tcp_keepalive(struct socket *sock);
diff --git a/net/rds/tcp_listen.c b/net/rds/tcp_listen.c
index 67d0929c7d3d..2c69a508a693 100644
--- a/net/rds/tcp_listen.c
+++ b/net/rds/tcp_listen.c
@@ -223,6 +223,9 @@ void rds_tcp_listen_data_ready(struct sock *sk)
* before it has been accepted and the accepter has set up their
* data_ready.. we only want to queue listen work for our listening
* socket
+ *
+ * (*ready)() may be null if we are racing with netns delete, and
+ * the listen socket is being torn down.
*/
if (sk->sk_state == TCP_LISTEN)
rds_tcp_accept_work(sk);
@@ -231,7 +234,8 @@ void rds_tcp_listen_data_ready(struct sock *sk)
out:
read_unlock_bh(&sk->sk_callback_lock);
- ready(sk);
+ if (ready)
+ ready(sk);
}
struct socket *rds_tcp_listen_init(struct net *net)
@@ -271,7 +275,7 @@ out:
return NULL;
}
-void rds_tcp_listen_stop(struct socket *sock)
+void rds_tcp_listen_stop(struct socket *sock, struct work_struct *acceptor)
{
struct sock *sk;
@@ -292,5 +296,6 @@ void rds_tcp_listen_stop(struct socket *sock)
/* wait for accepts to stop and close the socket */
flush_workqueue(rds_wq);
+ flush_work(acceptor);
sock_release(sock);
}