4.15-stable review patch. If anyone has any objections, please let me know.
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From: Sowmini Varadhan sowmini.varadhan@oracle.com
commit 681648e67d43cf269c5590ecf021ed481f4551fc upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- net/rds/connection.c | 3 ++- net/rds/rds.h | 6 +++--- net/rds/tcp.c | 4 ++-- 3 files changed, 7 insertions(+), 6 deletions(-)
--- a/net/rds/connection.c +++ b/net/rds/connection.c @@ -366,6 +366,8 @@ void rds_conn_shutdown(struct rds_conn_p * 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_connect */ rds_cong_remove_conn(conn);
- put_net(conn->c_net); kfree(conn->c_path); kmem_cache_free(rds_conn_slab, conn);
--- a/net/rds/rds.h +++ b/net/rds/rds.h @@ -150,7 +150,7 @@ struct rds_connection {
/* Protocol version */ unsigned int c_version; - struct net *c_net; + possible_net_t c_net;
struct list_head c_map_item; unsigned long c_map_queued; @@ -165,13 +165,13 @@ struct rds_connection { static inline struct net *rds_conn_net(struct rds_connection *conn) { - return conn->c_net; + return read_pnet(&conn->c_net); }
static inline void rds_conn_net_set(struct rds_connection *conn, struct net *net) { - conn->c_net = get_net(net); + write_pnet(&conn->c_net, net); }
#define RDS_FLAG_CONG_BITMAP 0x01 --- a/net/rds/tcp.c +++ b/net/rds/tcp.c @@ -528,7 +528,7 @@ static void rds_tcp_kill_sock(struct net rds_tcp_listen_stop(lsock, &rtn->rds_tcp_accept_w); spin_lock_irq(&rds_tcp_conn_lock); list_for_each_entry_safe(tc, _tc, &rds_tcp_conn_list, t_tcp_node) { - struct net *c_net = tc->t_cpath->cp_conn->c_net; + struct net *c_net = read_pnet(&tc->t_cpath->cp_conn->c_net);
if (net != c_net || !tc->t_sock) continue; @@ -587,7 +587,7 @@ static void rds_tcp_sysctl_reset(struct
spin_lock_irq(&rds_tcp_conn_lock); list_for_each_entry_safe(tc, _tc, &rds_tcp_conn_list, t_tcp_node) { - struct net *c_net = tc->t_cpath->cp_conn->c_net; + struct net *c_net = read_pnet(&tc->t_cpath->cp_conn->c_net);
if (net != c_net || !tc->t_sock) continue;