kernel.git/net/rds/connection.c, branch linux-4.16.y

rds: do not call ->conn_alloc with GFP_KERNEL

2018-02-13T18:52:02Z

Commit ebeeb1ad9b8a ("rds: tcp: use rds_destroy_pending() to synchronize netns/module teardown and rds connection/workq management") adds an rcu read critical section to __rd_conn_create. The memory allocations in that critcal section need to use GFP_ATOMIC to avoid sleeping. This patch was verified with syzkaller reproducer. Reported-by: syzbot+a0564419941aaae3fe3c@syzkaller.appspotmail.com Fixes: ebeeb1ad9b8a ("rds: tcp: use rds_destroy_pending() to synchronize netns/module teardown and rds connection/workq management") Signed-off-by: Sowmini Varadhan Acked-by: Santosh Shilimkar Signed-off-by: David S. Miller

rds: tcp: use rds_destroy_pending() to synchronize netns/module teardown and rds connection/workq management

2018-02-08T20:23:52Z

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) : /* code to pull out all the rds_connections that should be destroyed */ : 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 3db6e0d172c9 ("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 Acked-by: Santosh Shilimkar Signed-off-by: David S. Miller

rds: use RCU to synchronize work-enqueue with connection teardown

2018-01-05T18:39:18Z

rds_sendmsg() can enqueue work on cp_send_w from process context, but it should not enqueue this work if connection teardown has commenced (else we risk enquing work after rds_conn_path_destroy() has assumed that all work has been cancelled/flushed). Similarly some other functions like rds_cong_queue_updates and rds_tcp_data_ready are called in softirq context, and may end up enqueuing work on rds_wq after rds_conn_path_destroy() has assumed that all workqs are quiesced. Check the RDS_DESTROY_PENDING bit and use rcu synchronization to avoid all these races. Signed-off-by: Sowmini Varadhan Acked-by: Santosh Shilimkar Signed-off-by: David S. Miller

rds: Use atomic flag to track connections being destroyed

2018-01-05T18:39:18Z

Replace c_destroy_in_prog by using a bit in cp_flags that can set/tested atomically. Signed-off-by: Sowmini Varadhan Acked-by: Santosh Shilimkar Signed-off-by: David S. Miller

rds: debug: fix null check on static array

2017-12-06T20:02:48Z

t_name cannot be NULL since it is an array field of a struct. Replacing null check on static array with string length check using strnlen() Signed-off-by: Prashant Bhole Acked-by: Sowmini Varadhan Acked-by: Santosh Shilimkar Signed-off-by: David S. Miller

rds: tcp: correctly sequence cleanup on netns deletion.

2017-12-01T20:25:15Z

Commit 8edc3affc077 ("rds: tcp: Take explicit refcounts on struct net") introduces a regression in rds-tcp netns cleanup. The cleanup_net(), (and thus rds_tcp_dev_event notification) is only called from put_net() when all netns refcounts go to 0, but this cannot happen if the rds_connection itself is holding a c_net ref that it expects to release in rds_tcp_kill_sock. Instead, the rds_tcp_kill_sock callback should make sure to tear down state carefully, ensuring that the socket teardown is only done after all data-structures and workqs that depend on it are quiesced. The original motivation for commit 8edc3affc077 ("rds: tcp: Take explicit refcounts on struct net") was to resolve a race condition reported by syzkaller where workqs for tx/rx/connect were triggered after the namespace was deleted. Those worker threads should have been cancelled/flushed before socket tear-down and indeed, rds_conn_path_destroy() does try to sequence this by doing /* cancel cp_send_w */ /* cancel cp_recv_w */ /* flush cp_down_w */ /* free data structures */ Here the "flush cp_down_w" will trigger rds_conn_shutdown and thus invoke rds_tcp_conn_path_shutdown() to close the tcp socket, so that we ought to have satisfied the requirement that "socket-close is done after all other dependent state is quiesced". However, rds_conn_shutdown has a bug in that it *always* triggers the reconnect workq (and if connection is successful, we always restart tx/rx workqs so with the right timing, we risk the race conditions reported by syzkaller). Netns deletion is like module teardown- no need to restart a reconnect in this case. We can use the c_destroy_in_prog bit to avoid restarting the reconnect. Fixes: 8edc3affc077 ("rds: tcp: Take explicit refcounts on struct net") Signed-off-by: Sowmini Varadhan Acked-by: Santosh Shilimkar Signed-off-by: David S. Miller

rds: reduce memory footprint for RDS when transport is RDMA

2017-08-03T16:27:59Z

RDS over IB does not use multipath RDS, so the array of additional rds_conn_path structures is always superfluous in this case. Reduce the memory footprint of the rds module by making this a dynamic allocation predicated on whether the transport is mp_capable. Signed-off-by: Sowmini Varadhan Acked-by: Santosh Shilimkar Tested-by: Efrain Galaviz Signed-off-by: David S. Miller

rds: cancel send/recv work before queuing connection shutdown

2017-07-17T02:07:35Z

We could end up executing rds_conn_shutdown before the rds_recv_worker thread, then rds_conn_shutdown -> rds_tcp_conn_shutdown can do a sock_release and set sock->sk to null, which may interleave in bad ways with rds_recv_worker, e.g., it could result in: "BUG: unable to handle kernel NULL pointer dereference at 0000000000000078" [ffff881769f6fd70] release_sock at ffffffff815f337b [ffff881769f6fd90] rds_tcp_recv at ffffffffa043c888 [rds_tcp] [ffff881769f6fdb0] rds_recv_worker at ffffffffa04a4810 [rds] [ffff881769f6fde0] process_one_work at ffffffff810a14c1 [ffff881769f6fe40] worker_thread at ffffffff810a1940 [ffff881769f6fec0] kthread at ffffffff810a6b1e Also, do not enqueue any new shutdown workq items when the connection is shutting down (this may happen for rds-tcp in softirq mode, if a FIN or CLOSE is received while the modules is in the middle of an unload) Signed-off-by: Sowmini Varadhan Signed-off-by: David S. Miller

rds: tcp: set linger to 1 when unloading a rds-tcp

2017-06-22T15:34:04Z

If we are unloading the rds_tcp module, we can set linger to 1 and drop pending packets to accelerate reconnect. The peer will end up resetting the connection based on new generation numbers of the new incarnation, so hanging on to unsent TCP packets via linger is mostly pointless in this case. Signed-off-by: Sowmini Varadhan Tested-by: Jenny Xu Signed-off-by: David S. Miller

rds: tcp: remove cp_outgoing

2017-06-16T16:45:14Z

After commit 1a0e100fb2c9 ("RDS: TCP: Force every connection to be initiated by numerically smaller IP address") we no longer need the logic associated with cp_outgoing, so clean up usage of this field. Signed-off-by: Sowmini Varadhan Tested-by: Imanti Mendez Signed-off-by: David S. Miller