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

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This reverts commit b166a20b07.

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: syzbot+959223586843e69a2674@syzkaller.appspotmail.com
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Xin Long 2021-05-03 05:11:41 +08:00 • committed by David S. Miller
parent 2e9f60932a
commit 01bfe5e8e4
1 changed files with 8 additions and 5 deletions
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13
net/sctp/socket.c
View file

@ -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();