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Commit 90c1aff7 authored by David Windsor's avatar David Windsor Committed by Pablo Neira Ayuso
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ipvs: free ip_vs_dest structs when refcnt=0 



Currently, the ip_vs_dest cache frees ip_vs_dest objects when their
reference count becomes < 0.  Aside from not being semantically sound,
this is problematic for the new type refcount_t, which will be introduced
shortly in a separate patch. refcount_t is the new kernel type for
holding reference counts, and provides overflow protection and a
constrained interface relative to atomic_t (the type currently being
used for kernel reference counts).

Per Julian Anastasov: "The problem is that dest_trash currently holds
deleted dests (unlinked from RCU lists) with refcnt=0."  Changing
dest_trash to hold dest with refcnt=1 will allow us to free ip_vs_dest
structs when their refcnt=0, in ip_vs_dest_put_and_free().

Signed-off-by: default avatarDavid Windsor <dwindsor@gmail.com>
Signed-off-by: default avatarJulian Anastasov <ja@ssi.bg>
Signed-off-by: default avatarSimon Horman <horms@verge.net.au>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent a9e419dc

include/net/ip_vs.h

+1 −1
Original line number Diff line number Diff line
@@ -1421,7 +1421,7 @@ static inline void ip_vs_dest_put(struct ip_vs_dest *dest) 


static inline void ip_vs_dest_put_and_free(struct ip_vs_dest *dest)

{

	if (atomic_dec_return(&dest->refcnt) < 0)

	if (atomic_dec_and_test(&dest->refcnt))

		kfree(dest);

}

net/netfilter/ipvs/ip_vs_ctl.c

+3 −5
Original line number Diff line number Diff line
@@ -711,7 +711,6 @@ ip_vs_trash_get_dest(struct ip_vs_service *svc, int dest_af, 
		      dest->vport == svc->port))) {

			/* HIT */

			list_del(&dest->t_list);

			ip_vs_dest_hold(dest);

			goto out;

		}

	}
@@ -741,7 +740,7 @@ static void ip_vs_dest_free(struct ip_vs_dest *dest) 
 *  When the ip_vs_control_clearup is activated by ipvs module exit,

 *  the service tables must have been flushed and all the connections

 *  are expired, and the refcnt of each destination in the trash must

 *  be 0, so we simply release them here.

 *  be 1, so we simply release them here.

 */

static void ip_vs_trash_cleanup(struct netns_ipvs *ipvs)

{
@@ -1080,11 +1079,10 @@ static void __ip_vs_del_dest(struct netns_ipvs *ipvs, struct ip_vs_dest *dest, 
	if (list_empty(&ipvs->dest_trash) && !cleanup)

		mod_timer(&ipvs->dest_trash_timer,

			  jiffies + (IP_VS_DEST_TRASH_PERIOD >> 1));

	/* dest lives in trash without reference */

	/* dest lives in trash with reference */

	list_add(&dest->t_list, &ipvs->dest_trash);

	dest->idle_start = 0;

	spin_unlock_bh(&ipvs->dest_trash_lock);

	ip_vs_dest_put(dest);

}
@@ -1160,7 +1158,7 @@ static void ip_vs_dest_trash_expire(unsigned long data) 


	spin_lock(&ipvs->dest_trash_lock);

	list_for_each_entry_safe(dest, next, &ipvs->dest_trash, t_list) {

		if (atomic_read(&dest->refcnt) > 0)

		if (atomic_read(&dest->refcnt) > 1)

			continue;

		if (dest->idle_start) {

			if (time_before(now, dest->idle_start +