From fb3d89498d268c8dedc1ab5b15fa64f536564577 Mon Sep 17 00:00:00 2001 From: Neil Horman Date: Tue, 28 Jun 2005 15:40:02 -0700 Subject: [PATCH] [IPVS]: Close race conditions on ip_vs_conn_tab list modification 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. Signed-off-by: Neil Horman Acked-by: JulianAnastasov Signed-off-by: David S. Miller --- net/ipv4/ipvs/ip_vs_conn.c | 25 ++++--------------------- 1 file changed, 4 insertions(+), 21 deletions(-) diff --git a/net/ipv4/ipvs/ip_vs_conn.c b/net/ipv4/ipvs/ip_vs_conn.c index fd6feb5499fe..9f16ab309106 100644 --- a/net/ipv4/ipvs/ip_vs_conn.c +++ b/net/ipv4/ipvs/ip_vs_conn.c @@ -548,7 +548,6 @@ void ip_vs_conn_expire_now(struct ip_vs_conn *cp) { if (del_timer(&cp->timer)) mod_timer(&cp->timer, jiffies); - __ip_vs_conn_put(cp); } @@ -764,7 +763,6 @@ void ip_vs_random_dropentry(void) { int idx; struct ip_vs_conn *cp; - struct ip_vs_conn *ct; /* * Randomly scan 1/32 of the whole table every second @@ -801,21 +799,12 @@ void ip_vs_random_dropentry(void) continue; } - /* - * Drop the entry, and drop its ct if not referenced - */ - atomic_inc(&cp->refcnt); - ct_write_unlock(hash); - - if ((ct = cp->control)) - atomic_inc(&ct->refcnt); IP_VS_DBG(4, "del connection\n"); ip_vs_conn_expire_now(cp); - if (ct) { + if (cp->control) { IP_VS_DBG(4, "del conn template\n"); - ip_vs_conn_expire_now(ct); + ip_vs_conn_expire_now(cp->control); } - ct_write_lock(hash); } ct_write_unlock(hash); } @@ -829,7 +818,6 @@ static void ip_vs_conn_flush(void) { int idx; struct ip_vs_conn *cp; - struct ip_vs_conn *ct; flush_again: for (idx=0; idxrefcnt); - ct_write_unlock(idx); - if ((ct = cp->control)) - atomic_inc(&ct->refcnt); IP_VS_DBG(4, "del connection\n"); ip_vs_conn_expire_now(cp); - if (ct) { + if (cp->control) { IP_VS_DBG(4, "del conn template\n"); - ip_vs_conn_expire_now(ct); + ip_vs_conn_expire_now(cp->control); } - ct_write_lock(idx); } ct_write_unlock_bh(idx); } -- 2.20.1