[Patch] ipvs: close race conditions on ip_vs_conn_tab list modification

[Neil Horman]

Hello there-
	Patch to close a race condition in ip_vs_conn_flush.  In an smp system,
it is possible for an connection timer to expire, calling ip_vs_conn_expire
while the connection table is being flushed, before ct_write_lock_bh is
acquired.  Since the list iterator loop in ip_vs_con_flush releases and
re-acquires the spinlock (even though it doesn't re-enable softirqs), it is
possible for the expiration function to modify the connection list, while it is
being traversed in ip_vs_conn_flush.  The result is that the next pointer gets
set to NULL, and subsequently dereferenced, resulting in an oops.  This patch
removes the lock release and re-aquisition from the loop, closing the race
window.  Tested by myself, and those who origionally experienced the crash and
reported it to me, with successful results.

Signed-off-by: Neil Horman <nhorman@xxxxxxxxxx>

 ip_vs_conn.c |    2 --
 1 files changed, 2 deletions(-)

 
--- linux-2.6.git/net/ipv4/ipvs/ip_vs_conn.c.orig	2005-06-23 13:11:00.910372471 -0400
+++ linux-2.6.git/net/ipv4/ipvs/ip_vs_conn.c	2005-06-23 13:15:54.459852393 -0400
@@ -840,7 +838,6 @@
 
 		list_for_each_entry(cp, &ip_vs_conn_tab[idx], c_list) {
 			atomic_inc(&cp->refcnt);
-			ct_write_unlock(idx);
 
 			if ((ct = cp->control))
 				atomic_inc(&ct->refcnt);
@@ -850,7 +847,6 @@
 				IP_VS_DBG(4, "del conn template\n");
 				ip_vs_conn_expire_now(ct);
 			}
-			ct_write_lock(idx);
 		}
 		ct_write_unlock_bh(idx);
 	}
-- 
/***************************************************
 *Neil Horman
 *Software Engineer
 *Red Hat, Inc.
 *nhorman@xxxxxxxxxx
 *gpg keyid: 1024D / 0x92A74FA1
 *http://pgp.mit.edu
 ***************************************************/

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