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author | Sowmini Varadhan <sowmini.varadhan@oracle.com> | 2016-06-04 14:00:00 -0700 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2016-06-07 15:10:15 -0700 |
commit | 9c79440e2c5e2518879f1599270f64c3ddda3baf (patch) | |
tree | 69cbc888d7d91fe1e3c197443f608e35d54a4c30 | |
parent | 0b6f760cff04a7cdfafc3ec6915e91fed0533d8d (diff) | |
download | linux-stable-9c79440e2c5e2518879f1599270f64c3ddda3baf.tar.gz linux-stable-9c79440e2c5e2518879f1599270f64c3ddda3baf.tar.bz2 linux-stable-9c79440e2c5e2518879f1599270f64c3ddda3baf.zip |
RDS: TCP: fix race windows in send-path quiescence by rds_tcp_accept_one()
The send path needs to be quiesced before resetting callbacks from
rds_tcp_accept_one(), and commit eb192840266f ("RDS:TCP: Synchronize
rds_tcp_accept_one with rds_send_xmit when resetting t_sock") achieves
this using the c_state and RDS_IN_XMIT bit following the pattern
used by rds_conn_shutdown(). However this leaves the possibility
of a race window as shown in the sequence below
take t_conn_lock in rds_tcp_conn_connect
send outgoing syn to peer
drop t_conn_lock in rds_tcp_conn_connect
incoming from peer triggers rds_tcp_accept_one, conn is
marked CONNECTING
wait for RDS_IN_XMIT to quiesce any rds_send_xmit threads
call rds_tcp_reset_callbacks
[.. race-window where incoming syn-ack can cause the conn
to be marked UP from rds_tcp_state_change ..]
lock_sock called from rds_tcp_reset_callbacks, and we set
t_sock to null
As soon as the conn is marked UP in the race-window above, rds_send_xmit()
threads will proceed to rds_tcp_xmit and may encounter a null-pointer
deref on the t_sock.
Given that rds_tcp_state_change() is invoked in softirq context, whereas
rds_tcp_reset_callbacks() is in workq context, and testing for RDS_IN_XMIT
after lock_sock could result in a deadlock with tcp_sendmsg, this
commit fixes the race by using a new c_state, RDS_TCP_RESETTING, which
will prevent a transition to RDS_CONN_UP from rds_tcp_state_change().
Signed-off-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r-- | net/rds/rds.h | 2 | ||||
-rw-r--r-- | net/rds/tcp.c | 14 | ||||
-rw-r--r-- | net/rds/tcp_connect.c | 2 | ||||
-rw-r--r-- | net/rds/tcp_listen.c | 7 | ||||
-rw-r--r-- | net/rds/threads.c | 10 |
5 files changed, 27 insertions, 8 deletions
diff --git a/net/rds/rds.h b/net/rds/rds.h index 80256b08eac0..387df5f32e49 100644 --- a/net/rds/rds.h +++ b/net/rds/rds.h @@ -74,6 +74,7 @@ enum { RDS_CONN_CONNECTING, RDS_CONN_DISCONNECTING, RDS_CONN_UP, + RDS_CONN_RESETTING, RDS_CONN_ERROR, }; @@ -813,6 +814,7 @@ void rds_connect_worker(struct work_struct *); void rds_shutdown_worker(struct work_struct *); void rds_send_worker(struct work_struct *); void rds_recv_worker(struct work_struct *); +void rds_connect_path_complete(struct rds_connection *conn, int curr); void rds_connect_complete(struct rds_connection *conn); /* transport.c */ diff --git a/net/rds/tcp.c b/net/rds/tcp.c index 7ab1b41ffc88..74ee126a6fe6 100644 --- a/net/rds/tcp.c +++ b/net/rds/tcp.c @@ -148,11 +148,23 @@ void rds_tcp_reset_callbacks(struct socket *sock, * potentially have transitioned to the RDS_CONN_UP state, * so we must quiesce any send threads before resetting * c_transport_data. We quiesce these threads by setting - * cp_state to something other than RDS_CONN_UP, and then + * c_state to something other than RDS_CONN_UP, and then * waiting for any existing threads in rds_send_xmit to * complete release_in_xmit(). (Subsequent threads entering * rds_send_xmit() will bail on !rds_conn_up(). + * + * However an incoming syn-ack at this point would end up + * marking the conn as RDS_CONN_UP, and would again permit + * rds_send_xmi() threads through, so ideally we would + * synchronize on RDS_CONN_UP after lock_sock(), but cannot + * do that: waiting on !RDS_IN_XMIT after lock_sock() may + * end up deadlocking with tcp_sendmsg(), and the RDS_IN_XMIT + * would not get set. As a result, we set c_state to + * RDS_CONN_RESETTTING, to ensure that rds_tcp_state_change + * cannot mark rds_conn_path_up() in the window before lock_sock() */ + atomic_set(&conn->c_state, RDS_CONN_RESETTING); + wait_event(conn->c_waitq, !test_bit(RDS_IN_XMIT, &conn->c_flags)); lock_sock(osock->sk); /* reset receive side state for rds_tcp_data_recv() for osock */ if (tc->t_tinc) { diff --git a/net/rds/tcp_connect.c b/net/rds/tcp_connect.c index fb82e0a0bf89..fba13d0305fb 100644 --- a/net/rds/tcp_connect.c +++ b/net/rds/tcp_connect.c @@ -60,7 +60,7 @@ void rds_tcp_state_change(struct sock *sk) case TCP_SYN_RECV: break; case TCP_ESTABLISHED: - rds_connect_complete(conn); + rds_connect_path_complete(conn, RDS_CONN_CONNECTING); break; case TCP_CLOSE_WAIT: case TCP_CLOSE: diff --git a/net/rds/tcp_listen.c b/net/rds/tcp_listen.c index d9fe53675d95..686b1d03a558 100644 --- a/net/rds/tcp_listen.c +++ b/net/rds/tcp_listen.c @@ -135,16 +135,15 @@ int rds_tcp_accept_one(struct socket *sock) !conn->c_outgoing) { goto rst_nsk; } else { - atomic_set(&conn->c_state, RDS_CONN_CONNECTING); - wait_event(conn->c_waitq, - !test_bit(RDS_IN_XMIT, &conn->c_flags)); rds_tcp_reset_callbacks(new_sock, conn); conn->c_outgoing = 0; + /* rds_connect_path_complete() marks RDS_CONN_UP */ + rds_connect_path_complete(conn, RDS_CONN_DISCONNECTING); } } else { rds_tcp_set_callbacks(new_sock, conn); + rds_connect_path_complete(conn, RDS_CONN_CONNECTING); } - rds_connect_complete(conn); /* marks RDS_CONN_UP */ new_sock = NULL; ret = 0; goto out; diff --git a/net/rds/threads.c b/net/rds/threads.c index 454aa6d23327..4a323045719b 100644 --- a/net/rds/threads.c +++ b/net/rds/threads.c @@ -71,9 +71,9 @@ struct workqueue_struct *rds_wq; EXPORT_SYMBOL_GPL(rds_wq); -void rds_connect_complete(struct rds_connection *conn) +void rds_connect_path_complete(struct rds_connection *conn, int curr) { - if (!rds_conn_transition(conn, RDS_CONN_CONNECTING, RDS_CONN_UP)) { + if (!rds_conn_transition(conn, curr, RDS_CONN_UP)) { printk(KERN_WARNING "%s: Cannot transition to state UP, " "current state is %d\n", __func__, @@ -90,6 +90,12 @@ void rds_connect_complete(struct rds_connection *conn) queue_delayed_work(rds_wq, &conn->c_send_w, 0); queue_delayed_work(rds_wq, &conn->c_recv_w, 0); } +EXPORT_SYMBOL_GPL(rds_connect_path_complete); + +void rds_connect_complete(struct rds_connection *conn) +{ + rds_connect_path_complete(conn, RDS_CONN_CONNECTING); +} EXPORT_SYMBOL_GPL(rds_connect_complete); /* |