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

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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>
This commit is contained in:
Sowmini Varadhan 2017-11-30 11:11:29 -08:00 committed by David S. Miller
parent 681648e67d
commit f10b4cff98
2 changed files with 8 additions and 2 deletions
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9
net/rds/tcp.c
View file

@ -306,7 +306,8 @@ static void rds_tcp_conn_free(void *arg)
rdsdebug("freeing tc %p\n", tc);
spin_lock_irqsave(&rds_tcp_conn_lock, flags);
list_del(&tc->t_tcp_node);
if (!tc->t_tcp_node_detached)
list_del(&tc->t_tcp_node);
spin_unlock_irqrestore(&rds_tcp_conn_lock, flags);
kmem_cache_free(rds_tcp_conn_slab, tc);
@ -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)

1
net/rds/tcp.h
View file

@ -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