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![Sowmini Varadhan](/assets/img/avatar_default.png)
An rds_connection can get added during netns deletion between lines 528
and 529 of
506 static void rds_tcp_kill_sock(struct net *net)
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/* code to pull out all the rds_connections that should be destroyed */
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528 spin_unlock_irq(&rds_tcp_conn_lock);
529 list_for_each_entry_safe(tc, _tc, &tmp_list, t_tcp_node)
530 rds_conn_destroy(tc->t_cpath->cp_conn);
Such an rds_connection would miss out the rds_conn_destroy()
loop (that cancels all pending work) and (if it was scheduled
after netns deletion) could trigger the use-after-free.
A similar race-window exists for the module unload path
in rds_tcp_exit -> rds_tcp_destroy_conns
Concurrency with netns deletion (rds_tcp_kill_sock()) must be handled
by checking check_net() before enqueuing new work or adding new
connections.
Concurrency with module-unload is handled by maintaining a module
specific flag that is set at the start of the module exit function,
and must be checked before enqueuing new work or adding new connections.
This commit refactors existing RDS_DESTROY_PENDING checks added by
commit 3db6e0d172
("rds: use RCU to synchronize work-enqueue with
connection teardown") and consolidates all the concurrency checks
listed above into the function rds_destroy_pending().
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>
261 lines
7.8 KiB
C
261 lines
7.8 KiB
C
/*
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* Copyright (c) 2006 Oracle. All rights reserved.
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*
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* This software is available to you under a choice of one of two
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* licenses. You may choose to be licensed under the terms of the GNU
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* General Public License (GPL) Version 2, available from the file
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* COPYING in the main directory of this source tree, or the
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* OpenIB.org BSD license below:
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*
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* Redistribution and use in source and binary forms, with or
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* without modification, are permitted provided that the following
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* conditions are met:
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*
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* - Redistributions of source code must retain the above
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* copyright notice, this list of conditions and the following
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* disclaimer.
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*
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* - Redistributions in binary form must reproduce the above
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* copyright notice, this list of conditions and the following
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* disclaimer in the documentation and/or other materials
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* provided with the distribution.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*
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*/
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#include <linux/kernel.h>
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#include <linux/random.h>
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#include <linux/export.h>
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#include "rds.h"
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/*
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* All of connection management is simplified by serializing it through
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* work queues that execute in a connection managing thread.
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*
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* TCP wants to send acks through sendpage() in response to data_ready(),
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* but it needs a process context to do so.
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*
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* The receive paths need to allocate but can't drop packets (!) so we have
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* a thread around to block allocating if the receive fast path sees an
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* allocation failure.
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*/
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/* Grand Unified Theory of connection life cycle:
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* At any point in time, the connection can be in one of these states:
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* DOWN, CONNECTING, UP, DISCONNECTING, ERROR
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*
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* The following transitions are possible:
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* ANY -> ERROR
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* UP -> DISCONNECTING
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* ERROR -> DISCONNECTING
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* DISCONNECTING -> DOWN
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* DOWN -> CONNECTING
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* CONNECTING -> UP
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*
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* Transition to state DISCONNECTING/DOWN:
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* - Inside the shutdown worker; synchronizes with xmit path
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* through RDS_IN_XMIT, and with connection management callbacks
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* via c_cm_lock.
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*
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* For receive callbacks, we rely on the underlying transport
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* (TCP, IB/RDMA) to provide the necessary synchronisation.
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*/
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struct workqueue_struct *rds_wq;
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EXPORT_SYMBOL_GPL(rds_wq);
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void rds_connect_path_complete(struct rds_conn_path *cp, int curr)
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{
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if (!rds_conn_path_transition(cp, curr, RDS_CONN_UP)) {
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printk(KERN_WARNING "%s: Cannot transition to state UP, "
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"current state is %d\n",
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__func__,
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atomic_read(&cp->cp_state));
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rds_conn_path_drop(cp, false);
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return;
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}
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rdsdebug("conn %p for %pI4 to %pI4 complete\n",
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cp->cp_conn, &cp->cp_conn->c_laddr, &cp->cp_conn->c_faddr);
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cp->cp_reconnect_jiffies = 0;
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set_bit(0, &cp->cp_conn->c_map_queued);
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rcu_read_lock();
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if (!rds_destroy_pending(cp->cp_conn)) {
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queue_delayed_work(rds_wq, &cp->cp_send_w, 0);
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queue_delayed_work(rds_wq, &cp->cp_recv_w, 0);
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}
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rcu_read_unlock();
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}
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EXPORT_SYMBOL_GPL(rds_connect_path_complete);
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void rds_connect_complete(struct rds_connection *conn)
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{
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rds_connect_path_complete(&conn->c_path[0], RDS_CONN_CONNECTING);
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}
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EXPORT_SYMBOL_GPL(rds_connect_complete);
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/*
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* This random exponential backoff is relied on to eventually resolve racing
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* connects.
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*
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* If connect attempts race then both parties drop both connections and come
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* here to wait for a random amount of time before trying again. Eventually
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* the backoff range will be so much greater than the time it takes to
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* establish a connection that one of the pair will establish the connection
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* before the other's random delay fires.
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*
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* Connection attempts that arrive while a connection is already established
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* are also considered to be racing connects. This lets a connection from
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* a rebooted machine replace an existing stale connection before the transport
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* notices that the connection has failed.
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*
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* We should *always* start with a random backoff; otherwise a broken connection
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* will always take several iterations to be re-established.
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*/
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void rds_queue_reconnect(struct rds_conn_path *cp)
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{
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unsigned long rand;
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struct rds_connection *conn = cp->cp_conn;
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rdsdebug("conn %p for %pI4 to %pI4 reconnect jiffies %lu\n",
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conn, &conn->c_laddr, &conn->c_faddr,
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cp->cp_reconnect_jiffies);
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/* let peer with smaller addr initiate reconnect, to avoid duels */
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if (conn->c_trans->t_type == RDS_TRANS_TCP &&
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!IS_CANONICAL(conn->c_laddr, conn->c_faddr))
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return;
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set_bit(RDS_RECONNECT_PENDING, &cp->cp_flags);
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if (cp->cp_reconnect_jiffies == 0) {
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cp->cp_reconnect_jiffies = rds_sysctl_reconnect_min_jiffies;
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rcu_read_lock();
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if (!rds_destroy_pending(cp->cp_conn))
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queue_delayed_work(rds_wq, &cp->cp_conn_w, 0);
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rcu_read_unlock();
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return;
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}
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get_random_bytes(&rand, sizeof(rand));
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rdsdebug("%lu delay %lu ceil conn %p for %pI4 -> %pI4\n",
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rand % cp->cp_reconnect_jiffies, cp->cp_reconnect_jiffies,
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conn, &conn->c_laddr, &conn->c_faddr);
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rcu_read_lock();
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if (!rds_destroy_pending(cp->cp_conn))
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queue_delayed_work(rds_wq, &cp->cp_conn_w,
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rand % cp->cp_reconnect_jiffies);
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rcu_read_unlock();
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cp->cp_reconnect_jiffies = min(cp->cp_reconnect_jiffies * 2,
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rds_sysctl_reconnect_max_jiffies);
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}
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void rds_connect_worker(struct work_struct *work)
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{
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struct rds_conn_path *cp = container_of(work,
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struct rds_conn_path,
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cp_conn_w.work);
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struct rds_connection *conn = cp->cp_conn;
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int ret;
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if (cp->cp_index > 0 &&
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!IS_CANONICAL(cp->cp_conn->c_laddr, cp->cp_conn->c_faddr))
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return;
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clear_bit(RDS_RECONNECT_PENDING, &cp->cp_flags);
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ret = rds_conn_path_transition(cp, RDS_CONN_DOWN, RDS_CONN_CONNECTING);
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if (ret) {
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ret = conn->c_trans->conn_path_connect(cp);
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rdsdebug("conn %p for %pI4 to %pI4 dispatched, ret %d\n",
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conn, &conn->c_laddr, &conn->c_faddr, ret);
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if (ret) {
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if (rds_conn_path_transition(cp,
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RDS_CONN_CONNECTING,
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RDS_CONN_DOWN))
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rds_queue_reconnect(cp);
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else
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rds_conn_path_error(cp, "connect failed\n");
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}
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}
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}
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void rds_send_worker(struct work_struct *work)
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{
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struct rds_conn_path *cp = container_of(work,
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struct rds_conn_path,
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cp_send_w.work);
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int ret;
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if (rds_conn_path_state(cp) == RDS_CONN_UP) {
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clear_bit(RDS_LL_SEND_FULL, &cp->cp_flags);
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ret = rds_send_xmit(cp);
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cond_resched();
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rdsdebug("conn %p ret %d\n", cp->cp_conn, ret);
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switch (ret) {
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case -EAGAIN:
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rds_stats_inc(s_send_immediate_retry);
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queue_delayed_work(rds_wq, &cp->cp_send_w, 0);
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break;
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case -ENOMEM:
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rds_stats_inc(s_send_delayed_retry);
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queue_delayed_work(rds_wq, &cp->cp_send_w, 2);
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default:
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break;
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}
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}
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}
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void rds_recv_worker(struct work_struct *work)
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{
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struct rds_conn_path *cp = container_of(work,
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struct rds_conn_path,
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cp_recv_w.work);
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int ret;
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if (rds_conn_path_state(cp) == RDS_CONN_UP) {
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ret = cp->cp_conn->c_trans->recv_path(cp);
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rdsdebug("conn %p ret %d\n", cp->cp_conn, ret);
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switch (ret) {
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case -EAGAIN:
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rds_stats_inc(s_recv_immediate_retry);
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queue_delayed_work(rds_wq, &cp->cp_recv_w, 0);
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break;
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case -ENOMEM:
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rds_stats_inc(s_recv_delayed_retry);
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queue_delayed_work(rds_wq, &cp->cp_recv_w, 2);
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default:
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break;
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}
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}
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}
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void rds_shutdown_worker(struct work_struct *work)
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{
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struct rds_conn_path *cp = container_of(work,
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struct rds_conn_path,
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cp_down_w);
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rds_conn_shutdown(cp);
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}
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void rds_threads_exit(void)
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{
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destroy_workqueue(rds_wq);
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}
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int rds_threads_init(void)
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{
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rds_wq = create_singlethread_workqueue("krdsd");
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if (!rds_wq)
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return -ENOMEM;
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return 0;
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}
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