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| author | Sowmini Varadhan <sowmini.varadhan@oracle.com> | 2016-06-04 23:00:00 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2016-06-08 00:10:15 +0200 |
| commit | 9c79440e2c5e2518879f1599270f64c3ddda3baf (patch) | |
| tree | 69cbc888d7d91fe1e3c197443f608e35d54a4c30 /net/rds/rds.h | |
| parent | RDS: TCP: Retransmit half-sent datagrams when switching sockets in rds_tcp_re... (diff) | |
| download | linux-9c79440e2c5e2518879f1599270f64c3ddda3baf.tar.xz linux-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>
Diffstat (limited to 'net/rds/rds.h')
| -rw-r--r-- | net/rds/rds.h | 2 |
1 files changed, 2 insertions, 0 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 */ |