Commit f10b4cff authored Nov 30, 2017 by Sowmini Varadhan Committed by David S. Miller Dec 01, 2017

rds: tcp: atomically purge entries from rds_tcp_conn_list during netns delete



The rds_tcp_kill_sock() function parses the rds_tcp_conn_list
to find the rds_connection entries marked for deletion as part
of the netns deletion under the protection of the rds_tcp_conn_lock.
Since the rds_tcp_conn_list tracks rds_tcp_connections (which
have a 1:1 mapping with rds_conn_path), multiple tc entries in
the rds_tcp_conn_list will map to a single rds_connection, and will
be deleted as part of the rds_conn_destroy() operation that is
done outside the rds_tcp_conn_lock.

The rds_tcp_conn_list traversal done under the protection of
rds_tcp_conn_lock should not leave any doomed tc entries in
the list after the rds_tcp_conn_lock is released, else another
concurrently executiong netns delete (for a differnt netns) thread
may trip on these entries.

Reported-by: syzbot <syzkaller@googlegroups.com>
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>

parent 681648e6

net/rds/tcp.c

+7 −2

Original line number	Diff line number	Diff line
		@@ -306,6 +306,7 @@ static void rds_tcp_conn_free(void *arg)
		rdsdebug("freeing tc %p\n", tc);

		spin_lock_irqsave(&rds_tcp_conn_lock, flags);
		if (!tc->t_tcp_node_detached)
		list_del(&tc->t_tcp_node);
		spin_unlock_irqrestore(&rds_tcp_conn_lock, flags);

		@@ -510,8 +511,12 @@ static void rds_tcp_kill_sock(struct net *net)

		if (net != c_net \|\| !tc->t_sock)
		continue;
		if (!list_has_conn(&tmp_list, tc->t_cpath->cp_conn))
		if (!list_has_conn(&tmp_list, tc->t_cpath->cp_conn)) {
		list_move_tail(&tc->t_tcp_node, &tmp_list);
		} else {
		list_del(&tc->t_tcp_node);
		tc->t_tcp_node_detached = true;
		}
		}
		spin_unlock_irq(&rds_tcp_conn_lock);
		list_for_each_entry_safe(tc, _tc, &tmp_list, t_tcp_node)

net/rds/tcp.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -12,6 +12,7 @@ struct rds_tcp_incoming {
		struct rds_tcp_connection {

		struct list_head t_tcp_node;
		bool t_tcp_node_detached;
		struct rds_conn_path *t_cpath;
		/* t_conn_path_lock synchronizes the connection establishment between
		* rds_tcp_accept_one and rds_tcp_conn_path_connect