diff options
author | Sowmini Varadhan <sowmini.varadhan@oracle.com> | 2017-03-04 17:57:35 +0100 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2017-03-07 23:09:59 +0100 |
commit | b21dd4506b71bdb9c5a20e759255cd2513ea7ebe (patch) | |
tree | 47be3cbc15140e37dfe4778a227a7a377390fe90 /net/rds/tcp.c | |
parent | rds: tcp: Reorder initialization sequence in rds_tcp_init to avoid races (diff) | |
download | linux-b21dd4506b71bdb9c5a20e759255cd2513ea7ebe.tar.xz linux-b21dd4506b71bdb9c5a20e759255cd2513ea7ebe.zip |
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/rds/tcp.c')
-rw-r--r-- | net/rds/tcp.c | 15 |
1 files changed, 10 insertions, 5 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, |