Commit 01bfe5e8 authored by Xin Long's avatar Xin Long Committed by David S. Miller
Browse files

Revert "net/sctp: fix race condition in sctp_destroy_sock" 



This reverts commit b166a20b.

This one has to be reverted as it introduced a dead lock, as
syzbot reported:

       CPU0                    CPU1
       ----                    ----
  lock(&net->sctp.addr_wq_lock);
                               lock(slock-AF_INET6);
                               lock(&net->sctp.addr_wq_lock);
  lock(slock-AF_INET6);

CPU0 is the thread of sctp_addr_wq_timeout_handler(), and CPU1
is that of sctp_close().

The original issue this commit fixed will be fixed in the next
patch.

Reported-by: default avatar <syzbot+959223586843e69a2674@syzkaller.appspotmail.com>
Signed-off-by: default avatarXin Long <lucien.xin@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 2e9f6093

net/sctp/socket.c

+8 −5
Original line number Diff line number Diff line
@@ -1520,9 +1520,11 @@ static void sctp_close(struct sock *sk, long timeout) 


	/* Supposedly, no process has access to the socket, but

	 * the net layers still may.

	 * Also, sctp_destroy_sock() needs to be called with addr_wq_lock

	 * held and that should be grabbed before socket lock.

	 */

	local_bh_disable();

	bh_lock_sock(sk);

	spin_lock_bh(&net->sctp.addr_wq_lock);

	bh_lock_sock_nested(sk);



	/* Hold the sock, since sk_common_release() will put sock_put()

	 * and we have just a little more cleanup.
@@ -1531,7 +1533,7 @@ static void sctp_close(struct sock *sk, long timeout) 
	sk_common_release(sk);



	bh_unlock_sock(sk);

	local_bh_enable();

	spin_unlock_bh(&net->sctp.addr_wq_lock);



	sock_put(sk);
@@ -4991,6 +4993,9 @@ static int sctp_init_sock(struct sock *sk) 
	sk_sockets_allocated_inc(sk);

	sock_prot_inuse_add(net, sk->sk_prot, 1);



	/* Nothing can fail after this block, otherwise

	 * sctp_destroy_sock() will be called without addr_wq_lock held

	 */

	if (net->sctp.default_auto_asconf) {

		spin_lock(&sock_net(sk)->sctp.addr_wq_lock);

		list_add_tail(&sp->auto_asconf_list,
@@ -5025,9 +5030,7 @@ static void sctp_destroy_sock(struct sock *sk) 


	if (sp->do_auto_asconf) {

		sp->do_auto_asconf = 0;

		spin_lock_bh(&sock_net(sk)->sctp.addr_wq_lock);

		list_del(&sp->auto_asconf_list);

		spin_unlock_bh(&sock_net(sk)->sctp.addr_wq_lock);

	}

	sctp_endpoint_free(sp->ep);

	local_bh_disable();