sctp: fix ASCONF list handling
->auto_asconf_splist is per namespace and mangled by functions like
sctp_setsockopt_auto_asconf() which doesn't guarantee any serialization.
Also, the call to inet_sk_copy_descendant() was backuping
->auto_asconf_list through the copy but was not honoring
->do_auto_asconf, which could lead to list corruption if it was
different between both sockets.
This commit thus fixes the list handling by using ->addr_wq_lock
spinlock to protect the list. A special handling is done upon socket
creation and destruction for that. Error handlig on sctp_init_sock()
will never return an error after having initialized asconf, so
sctp_destroy_sock() can be called without addrq_wq_lock. The lock now
will be take on sctp_close_sock(), before locking the socket, so we
don't do it in inverse order compared to sctp_addr_wq_timeout_handler().
Instead of taking the lock on sctp_sock_migrate() for copying and
restoring the list values, it's preferred to avoid rewritting it by
implementing sctp_copy_descendant().
Issue was found with a test application that kept flipping sysctl
default_auto_asconf on and off, but one could trigger it by issuing
simultaneous setsockopt() calls on multiple sockets or by
creating/destroying sockets fast enough. This is only triggerable
locally.
Fixes: 9f7d653b67ae ("sctp: Add Auto-ASCONF support (core).")
Reported-by: Ji Jianwen <jiji@redhat.com>
Suggested-by: Neil Horman <nhorman@tuxdriver.com>
Suggested-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index f09de7f..5f6c4e6 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -1528,8 +1528,10 @@
/* 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();
+ spin_lock_bh(&net->sctp.addr_wq_lock);
bh_lock_sock(sk);
/* Hold the sock, since sk_common_release() will put sock_put()
@@ -1539,7 +1541,7 @@
sk_common_release(sk);
bh_unlock_sock(sk);
- local_bh_enable();
+ spin_unlock_bh(&net->sctp.addr_wq_lock);
sock_put(sk);
@@ -3580,6 +3582,7 @@
if ((val && sp->do_auto_asconf) || (!val && !sp->do_auto_asconf))
return 0;
+ spin_lock_bh(&sock_net(sk)->sctp.addr_wq_lock);
if (val == 0 && sp->do_auto_asconf) {
list_del(&sp->auto_asconf_list);
sp->do_auto_asconf = 0;
@@ -3588,6 +3591,7 @@
&sock_net(sk)->sctp.auto_asconf_splist);
sp->do_auto_asconf = 1;
}
+ spin_unlock_bh(&sock_net(sk)->sctp.addr_wq_lock);
return 0;
}
@@ -4121,18 +4125,28 @@
local_bh_disable();
percpu_counter_inc(&sctp_sockets_allocated);
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,
&net->sctp.auto_asconf_splist);
sp->do_auto_asconf = 1;
- } else
+ spin_unlock(&sock_net(sk)->sctp.addr_wq_lock);
+ } else {
sp->do_auto_asconf = 0;
+ }
+
local_bh_enable();
return 0;
}
-/* Cleanup any SCTP per socket resources. */
+/* Cleanup any SCTP per socket resources. Must be called with
+ * sock_net(sk)->sctp.addr_wq_lock held if sp->do_auto_asconf is true
+ */
static void sctp_destroy_sock(struct sock *sk)
{
struct sctp_sock *sp;
@@ -7195,6 +7209,19 @@
newinet->mc_list = NULL;
}
+static inline void sctp_copy_descendant(struct sock *sk_to,
+ const struct sock *sk_from)
+{
+ int ancestor_size = sizeof(struct inet_sock) +
+ sizeof(struct sctp_sock) -
+ offsetof(struct sctp_sock, auto_asconf_list);
+
+ if (sk_from->sk_family == PF_INET6)
+ ancestor_size += sizeof(struct ipv6_pinfo);
+
+ __inet_sk_copy_descendant(sk_to, sk_from, ancestor_size);
+}
+
/* Populate the fields of the newsk from the oldsk and migrate the assoc
* and its messages to the newsk.
*/
@@ -7209,7 +7236,6 @@
struct sk_buff *skb, *tmp;
struct sctp_ulpevent *event;
struct sctp_bind_hashbucket *head;
- struct list_head tmplist;
/* Migrate socket buffer sizes and all the socket level options to the
* new socket.
@@ -7217,12 +7243,7 @@
newsk->sk_sndbuf = oldsk->sk_sndbuf;
newsk->sk_rcvbuf = oldsk->sk_rcvbuf;
/* Brute force copy old sctp opt. */
- if (oldsp->do_auto_asconf) {
- memcpy(&tmplist, &newsp->auto_asconf_list, sizeof(tmplist));
- inet_sk_copy_descendant(newsk, oldsk);
- memcpy(&newsp->auto_asconf_list, &tmplist, sizeof(tmplist));
- } else
- inet_sk_copy_descendant(newsk, oldsk);
+ sctp_copy_descendant(newsk, oldsk);
/* Restore the ep value that was overwritten with the above structure
* copy.
