[PATCH 4.0 09/55] sctp: fix ASCONF list handling

Greg Kroah-Hartman
2015-07-08T08:05:12Z

From: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>

[ Upstream commit 2d45a02d0166caf2627fe91897c6ffc3b19514c4 ]

->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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/net/netns/sctp.h | 1 +
include/net/sctp/structs.h | 4 ++++
net/sctp/socket.c | 43 ++++++++++++++++++++++++++++++++-----------
3 files changed, 37 insertions(+), 11 deletions(-)

--- a/include/net/netns/sctp.h
+++ b/include/net/netns/sctp.h
@@ -31,6 +31,7 @@ struct netns_sctp {
struct list_head addr_waitq;
struct timer_list addr_wq_timer;
struct list_head auto_asconf_splist;
+ /* Lock that protects both addr_waitq and auto_asconf_splist */
spinlock_t addr_wq_lock;

/* Lock that protects the local_addr_list writers */
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -223,6 +223,10 @@ struct sctp_sock {
atomic_t pd_mode;
/* Receive to here while partial delivery is in effect. */
struct sk_buff_head pd_lobby;
+
+ /* These must be the last fields, as they will skipped on copies,
+ * like on accept and peeloff operations
+ */
struct list_head auto_asconf_list;
int do_auto_asconf;
};
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -1533,8 +1533,10 @@ static void sctp_close(struct sock *sk,

/* 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()
@@ -1544,7 +1546,7 @@ static void sctp_close(struct sock *sk,
sk_common_release(sk);

bh_unlock_sock(sk);
- local_bh_enable();
+ spin_unlock_bh(&net->sctp.addr_wq_lock);

sock_put(sk);

@@ -3587,6 +3589,7 @@ static int sctp_setsockopt_auto_asconf(s
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;
@@ -3595,6 +3598,7 @@ static int sctp_setsockopt_auto_asconf(s
&sock_net(sk)->sctp.auto_asconf_splist);
sp->do_auto_asconf = 1;
}
+ spin_unlock_bh(&sock_net(sk)->sctp.addr_wq_lock);
return 0;
}

@@ -4128,18 +4132,28 @@ static int sctp_init_sock(struct sock *s
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;
@@ -7202,6 +7216,19 @@ void sctp_copy_sock(struct sock *newsk,
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.
*/
@@ -7216,7 +7243,6 @@ static void sctp_sock_migrate(struct soc
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.
@@ -7224,12 +7250,7 @@ static void sctp_sock_migrate(struct soc
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.