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Merge branch 'sctp-race-fix'

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Xin Long says:

====================
sctp: fix the race condition in sctp_destroy_sock in a proper way

The original fix introduced a dead lock, and has to be removed in
Patch 1/2, and we will get a proper way to fix it in Patch 2/2.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2021-05-03 13:36:21 -07:00
commit d89ecd154c
1 changed files with 22 additions and 16 deletions
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38
net/sctp/socket.c
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@ -357,6 +357,18 @@ static struct sctp_af *sctp_sockaddr_af(struct sctp_sock *opt,
return af; return af;
} }
static void sctp_auto_asconf_init(struct sctp_sock *sp)
{
struct net *net = sock_net(&sp->inet.sk);
if (net->sctp.default_auto_asconf) {
spin_lock(&net->sctp.addr_wq_lock);
list_add_tail(&sp->auto_asconf_list, &net->sctp.auto_asconf_splist);
spin_unlock(&net->sctp.addr_wq_lock);
sp->do_auto_asconf = 1;
}
}
/* Bind a local address either to an endpoint or to an association. */ /* Bind a local address either to an endpoint or to an association. */
static int sctp_do_bind(struct sock *sk, union sctp_addr *addr, int len) static int sctp_do_bind(struct sock *sk, union sctp_addr *addr, int len)
{ {
@ -418,8 +430,10 @@ static int sctp_do_bind(struct sock *sk, union sctp_addr *addr, int len)
return -EADDRINUSE; return -EADDRINUSE;
/* Refresh ephemeral port. */ /* Refresh ephemeral port. */
if (!bp->port) if (!bp->port) {
bp->port = inet_sk(sk)->inet_num; bp->port = inet_sk(sk)->inet_num;
sctp_auto_asconf_init(sp);
}
/* Add the address to the bind address list. /* Add the address to the bind address list.
* Use GFP_ATOMIC since BHs will be disabled. * Use GFP_ATOMIC since BHs will be disabled.
@ -1520,9 +1534,11 @@ static void sctp_close(struct sock *sk, long timeout)
/* Supposedly, no process has access to the socket, but /* Supposedly, no process has access to the socket, but
* the net layers still may. * 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(); spin_lock_bh(&net->sctp.addr_wq_lock);
bh_lock_sock(sk); bh_lock_sock_nested(sk);
/* Hold the sock, since sk_common_release() will put sock_put() /* Hold the sock, since sk_common_release() will put sock_put()
* and we have just a little more cleanup. * and we have just a little more cleanup.
@ -1531,7 +1547,7 @@ static void sctp_close(struct sock *sk, long timeout)
sk_common_release(sk); sk_common_release(sk);
bh_unlock_sock(sk); bh_unlock_sock(sk);
local_bh_enable(); spin_unlock_bh(&net->sctp.addr_wq_lock);
sock_put(sk); sock_put(sk);
@ -4991,16 +5007,6 @@ static int sctp_init_sock(struct sock *sk)
sk_sockets_allocated_inc(sk); sk_sockets_allocated_inc(sk);
sock_prot_inuse_add(net, sk->sk_prot, 1); sock_prot_inuse_add(net, sk->sk_prot, 1);
if (net->sctp.default_auto_asconf) {
spin_lock(&sock_net(sk)->sctp.addr_wq_lock);
list_add_tail(&sp->auto_asconf_list,
&net->sctp.auto_asconf_splist);
sp->do_auto_asconf = 1;
spin_unlock(&sock_net(sk)->sctp.addr_wq_lock);
} else {
sp->do_auto_asconf = 0;
}
local_bh_enable(); local_bh_enable();
return 0; return 0;
@ -5025,9 +5031,7 @@ static void sctp_destroy_sock(struct sock *sk)
if (sp->do_auto_asconf) { if (sp->do_auto_asconf) {
sp->do_auto_asconf = 0; sp->do_auto_asconf = 0;
spin_lock_bh(&sock_net(sk)->sctp.addr_wq_lock);
list_del(&sp->auto_asconf_list); list_del(&sp->auto_asconf_list);
spin_unlock_bh(&sock_net(sk)->sctp.addr_wq_lock);
} }
sctp_endpoint_free(sp->ep); sctp_endpoint_free(sp->ep);
local_bh_disable(); local_bh_disable();
@ -9398,6 +9402,8 @@ static int sctp_sock_migrate(struct sock *oldsk, struct sock *newsk,
return err; return err;
} }
sctp_auto_asconf_init(newsp);
/* Move any messages in the old socket's receive queue that are for the /* Move any messages in the old socket's receive queue that are for the
* peeled off association to the new socket's receive queue. * peeled off association to the new socket's receive queue.
*/ */