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authorSowmini Varadhan <sowmini.varadhan@oracle.com>2017-11-30 22:11:28 +0300
committerDavid S. Miller <davem@davemloft.net>2017-12-01 23:25:15 +0300
commit681648e67d43cf269c5590ecf021ed481f4551fc (patch)
tree834b2c6ccc03c66ce9c4cd98c30a2efc7578f5c0 /net/rds/connection.c
parent2d746c93b6e55d34a98c8983b30d991707a2059b (diff)
downloadlinux-681648e67d43cf269c5590ecf021ed481f4551fc.tar.xz
rds: tcp: correctly sequence cleanup on netns deletion.
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 <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/connection.c')
-rw-r--r--net/rds/connection.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/net/rds/connection.c b/net/rds/connection.c
index 7ee2d5d68b78..9efc82c665b5 100644
--- a/net/rds/connection.c
+++ b/net/rds/connection.c
@@ -366,6 +366,8 @@ void rds_conn_shutdown(struct rds_conn_path *cp)
* to the conn hash, so we never trigger a reconnect on this
* conn - the reconnect is always triggered by the active peer. */
cancel_delayed_work_sync(&cp->cp_conn_w);
+ if (conn->c_destroy_in_prog)
+ return;
rcu_read_lock();
if (!hlist_unhashed(&conn->c_hash_node)) {
rcu_read_unlock();
@@ -445,7 +447,6 @@ void rds_conn_destroy(struct rds_connection *conn)
*/
rds_cong_remove_conn(conn);
- put_net(conn->c_net);
kfree(conn->c_path);
kmem_cache_free(rds_conn_slab, conn);