sctp: Fix a race between ICMP protocol unreachable and connect()

ICMP protocol unreachable handling completely disregarded
the fact that the user may have locked the socket.  It proceeded
to destroy the association, even though the user may have
held the lock and had a ref on the association.  This resulted
in the following:

Attempt to release alive inet socket f6afcc00

=========================
[ 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>

1 files changed, 18 insertions, 4 deletions

diff --git a/net/sctp/input.c b/net/sctp/input.c
index 2a570184e5a9..ea2192444ce6 100644
--- a/net/sctp/input.c
+++ b/net/sctp/input.c
@@ -440,11 +440,25 @@ 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. */