[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 <nhorman@redhat.com>
Acked-by: JulianAnastasov
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/ipvs/ip_vs_conn.c b/net/ipv4/ipvs/ip_vs_conn.c
index fd6feb5..9f16ab3 100644
--- a/net/ipv4/ipvs/ip_vs_conn.c
+++ b/net/ipv4/ipvs/ip_vs_conn.c
@@ -548,7 +548,6 @@
{
if (del_timer(&cp->timer))
mod_timer(&cp->timer, jiffies);
- __ip_vs_conn_put(cp);
}
@@ -764,7 +763,6 @@
{
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 @@
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 @@
{
int idx;
struct ip_vs_conn *cp;
- struct ip_vs_conn *ct;
flush_again:
for (idx=0; idx<IP_VS_CONN_TAB_SIZE; idx++) {
@@ -839,18 +827,13 @@
ct_write_lock_bh(idx);
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);
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);
}