[lucid/fsl-imx51,CVE,1/1] sctp: Fix a race between ICMP protocol unreachable and connect()

=========================
[ BUG: held lock freed! ]
-------------------------
somenu/2672 is freeing memory f6afcc00-f6afcfff, with a lock still held
there!
 (sk_lock-AF_INET){+.+.+.}, at: [<c122098a>] sctp_connect+0x13/0x4c
1 lock held by somenu/2672:
 #0:  (sk_lock-AF_INET){+.+.+.}, at: [<c122098a>] sctp_connect+0x13/0x4c

stack backtrace:
Pid: 2672, comm: somenu Not tainted 2.6.32-telco #55
Call Trace:
 [<c1232266>] ? printk+0xf/0x11
 [<c1038553>] debug_check_no_locks_freed+0xce/0xff
 [<c10620b4>] kmem_cache_free+0x21/0x66
 [<c1185f25>] __sk_free+0x9d/0xab
 [<c1185f9c>] sk_free+0x1c/0x1e
 [<c1216e38>] sctp_association_put+0x32/0x89
 [<c1220865>] __sctp_connect+0x36d/0x3f4
 [<c122098a>] ? sctp_connect+0x13/0x4c
 [<c102d073>] ? autoremove_wake_function+0x0/0x33
 [<c12209a8>] sctp_connect+0x31/0x4c
 [<c11d1e80>] inet_dgram_connect+0x4b/0x55
 [<c11834fa>] sys_connect+0x54/0x71
 [<c103a3a2>] ? lock_release_non_nested+0x88/0x239
 [<c1054026>] ? might_fault+0x42/0x7c
 [<c1054026>] ? might_fault+0x42/0x7c
 [<c11847ab>] sys_socketcall+0x6d/0x178
 [<c10da994>] ? trace_hardirqs_on_thunk+0xc/0x10
 [<c1002959>] syscall_call+0x7/0xb

This was because the sctp_wait_for_connect() would aqcure the socket
lock and then proceed to release the last reference count on the
association, thus cause the fully destruction path to finish freeing
the socket.

The simplest solution is to start a very short timer in case the socket
is owned by user.  When the timer expires, we can do some verification
and be able to do the release properly.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 50b5d6ad63821cea324a5a7a19854d4de1a0a819)
---
 include/net/sctp/sm.h      |    1 +
 include/net/sctp/structs.h |    3 +++
 net/sctp/input.c           |   22 ++++++++++++++++++----
 net/sctp/sm_sideeffect.c   |   35 +++++++++++++++++++++++++++++++++++
 net/sctp/transport.c       |    2 ++
 5 files changed, 59 insertions(+), 4 deletions(-)

diff --git a/include/net/sctp/sm.h b/include/net/sctp/sm.h
index c1dd893..76abe6c 100644
--- a/include/net/sctp/sm.h
+++ b/include/net/sctp/sm.h
@@ -278,6 +278,7 @@  int sctp_do_sm(sctp_event_t event_type, sctp_subtype_t subtype,
 /* 2nd level prototypes */
 void sctp_generate_t3_rtx_event(unsigned long peer);
 void sctp_generate_heartbeat_event(unsigned long peer);
+void sctp_generate_proto_unreach_event(unsigned long peer);
 
 void sctp_ootb_pkt_free(struct sctp_packet *);
 
diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index 3da3a69..a83eee3 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -1008,6 +1008,9 @@  struct sctp_transport {
 	/* Heartbeat timer is per destination. */
 	struct timer_list hb_timer;
 
+	/* Timer to handle ICMP proto unreachable envets */
+	struct timer_list proto_unreach_timer;
+
 	/* Since we're using per-destination retransmission timers
 	 * (see above), we're also using per-destination "transmitted"
 	 * queues.  This probably ought to be a private struct
diff --git a/net/sctp/input.c b/net/sctp/input.c
index c0c973e..4ffaf57 100644
--- a/net/sctp/input.c
+++ b/net/sctp/input.c
@@ -427,11 +427,25 @@  void sctp_icmp_proto_unreachable(struct sock *sk,
 {
 	SCTP_DEBUG_PRINTK("%s\n",  __func__);
 
-	sctp_do_sm(SCTP_EVENT_T_OTHER,
-		   SCTP_ST_OTHER(SCTP_EVENT_ICMP_PROTO_UNREACH),
-		   asoc->state, asoc->ep, asoc, t,
-		   GFP_ATOMIC);
+	if (sock_owned_by_user(sk)) {
+		if (timer_pending(&t->proto_unreach_timer))
+			return;
+		else {
+			if (!mod_timer(&t->proto_unreach_timer,
+						jiffies + (HZ/20)))
+				sctp_association_hold(asoc);
+		}
+			
+	} else {
+		if (timer_pending(&t->proto_unreach_timer) &&
+		    del_timer(&t->proto_unreach_timer))
+			sctp_association_put(asoc);
 
+		sctp_do_sm(SCTP_EVENT_T_OTHER,
+			   SCTP_ST_OTHER(SCTP_EVENT_ICMP_PROTO_UNREACH),
+			   asoc->state, asoc->ep, asoc, t,
+			   GFP_ATOMIC);
+	}
 }
 
 /* Common lookup code for icmp/icmpv6 error handler. */
diff --git a/net/sctp/sm_sideeffect.c b/net/sctp/sm_sideeffect.c
index 86426aa..25c0131 100644
--- a/net/sctp/sm_sideeffect.c
+++ b/net/sctp/sm_sideeffect.c
@@ -397,6 +397,41 @@  out_unlock:
 	sctp_transport_put(transport);
 }
 
+/* Handle the timeout of the ICMP protocol unreachable timer.  Trigger
+ * the correct state machine transition that will close the association.
+ */
+void sctp_generate_proto_unreach_event(unsigned long data)
+{
+	struct sctp_transport *transport = (struct sctp_transport *) data;
+	struct sctp_association *asoc = transport->asoc;
+	
+	sctp_bh_lock_sock(asoc->base.sk);
+	if (sock_owned_by_user(asoc->base.sk)) {
+		SCTP_DEBUG_PRINTK("%s:Sock is busy.\n", __func__);
+
+		/* Try again later.  */
+		if (!mod_timer(&transport->proto_unreach_timer,
+				jiffies + (HZ/20)))
+			sctp_association_hold(asoc);
+		goto out_unlock;
+	}
+
+	/* Is this structure just waiting around for us to actually
+	 * get destroyed?
+	 */
+	if (asoc->base.dead)
+		goto out_unlock;
+
+	sctp_do_sm(SCTP_EVENT_T_OTHER,
+		   SCTP_ST_OTHER(SCTP_EVENT_ICMP_PROTO_UNREACH),
+		   asoc->state, asoc->ep, asoc, transport, GFP_ATOMIC);
+
+out_unlock:
+	sctp_bh_unlock_sock(asoc->base.sk);
+	sctp_association_put(asoc);
+}
+
+
 /* Inject a SACK Timeout event into the state machine.  */
 static void sctp_generate_sack_event(unsigned long data)
 {
diff --git a/net/sctp/transport.c b/net/sctp/transport.c
index e5dde45..8312b56 100644
--- a/net/sctp/transport.c
+++ b/net/sctp/transport.c
@@ -108,6 +108,8 @@  static struct sctp_transport *sctp_transport_init(struct sctp_transport *peer,
 			(unsigned long)peer);
 	setup_timer(&peer->hb_timer, sctp_generate_heartbeat_event,
 			(unsigned long)peer);
+	setup_timer(&peer->proto_unreach_timer,
+		    sctp_generate_proto_unreach_event, (unsigned long)peer);
 
 	/* Initialize the 64-bit random nonce sent with heartbeat. */
 	get_random_bytes(&peer->hb_nonce, sizeof(peer->hb_nonce));