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Commit ef8531b6 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

xfrm: fix RCU bugs 



This patch reverts commit 56892261 (xfrm: Use rcu_dereference_bh to
deference pointer protected by rcu_read_lock_bh), and fixes bugs
introduced in commit 418a99ac ( Replace rwlock on xfrm_policy_afinfo
with rcu )

1) We properly use RCU variant in this file, not a mix of RCU/RCU_BH

2) We must defer some writes after the synchronize_rcu() call or a reader
 can crash dereferencing NULL pointer.

3) Now we use the xfrm_policy_afinfo_lock spinlock only from process
context, we no longer need to block BH in xfrm_policy_register_afinfo()
and xfrm_policy_unregister_afinfo()

4) Can use RCU_INIT_POINTER() instead of rcu_assign_pointer() in
xfrm_policy_unregister_afinfo()

5) Remove a forward inline declaration (xfrm_policy_put_afinfo()),
  and also move xfrm_policy_get_afinfo() declaration.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Cc: Fan Du <fan.du@windriver.com>
Cc: Priyanka Jain <Priyanka.Jain@freescale.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 0115e8e3

net/xfrm/xfrm_policy.c

+39 −37
Original line number Diff line number Diff line
@@ -48,8 +48,6 @@ static struct xfrm_policy_afinfo __rcu *xfrm_policy_afinfo[NPROTO] 


static struct kmem_cache *xfrm_dst_cache __read_mostly;



static struct xfrm_policy_afinfo *xfrm_policy_get_afinfo(unsigned short family);

static inline void xfrm_policy_put_afinfo(struct xfrm_policy_afinfo *afinfo);

static void xfrm_init_pmtu(struct dst_entry *dst);

static int stale_bundle(struct dst_entry *dst);

static int xfrm_bundle_ok(struct xfrm_dst *xdst);
@@ -96,6 +94,24 @@ bool xfrm_selector_match(const struct xfrm_selector *sel, const struct flowi *fl 
	return false;

}



static struct xfrm_policy_afinfo *xfrm_policy_get_afinfo(unsigned short family)

{

	struct xfrm_policy_afinfo *afinfo;



	if (unlikely(family >= NPROTO))

		return NULL;

	rcu_read_lock();

	afinfo = rcu_dereference(xfrm_policy_afinfo[family]);

	if (unlikely(!afinfo))

		rcu_read_unlock();

	return afinfo;

}



static void xfrm_policy_put_afinfo(struct xfrm_policy_afinfo *afinfo)

{

	rcu_read_unlock();

}



static inline struct dst_entry *__xfrm_dst_lookup(struct net *net, int tos,

						  const xfrm_address_t *saddr,

						  const xfrm_address_t *daddr,
@@ -2421,7 +2437,7 @@ int xfrm_policy_register_afinfo(struct xfrm_policy_afinfo *afinfo) 
		return -EINVAL;

	if (unlikely(afinfo->family >= NPROTO))

		return -EAFNOSUPPORT;

	spin_lock_bh(&xfrm_policy_afinfo_lock);

	spin_lock(&xfrm_policy_afinfo_lock);

	if (unlikely(xfrm_policy_afinfo[afinfo->family] != NULL))

		err = -ENOBUFS;

	else {
@@ -2444,7 +2460,7 @@ int xfrm_policy_register_afinfo(struct xfrm_policy_afinfo *afinfo) 
			afinfo->garbage_collect = xfrm_garbage_collect_deferred;

		rcu_assign_pointer(xfrm_policy_afinfo[afinfo->family], afinfo);

	}

	spin_unlock_bh(&xfrm_policy_afinfo_lock);

	spin_unlock(&xfrm_policy_afinfo_lock);



	rtnl_lock();

	for_each_net(net) {
@@ -2477,23 +2493,26 @@ int xfrm_policy_unregister_afinfo(struct xfrm_policy_afinfo *afinfo) 
		return -EINVAL;

	if (unlikely(afinfo->family >= NPROTO))

		return -EAFNOSUPPORT;

	spin_lock_bh(&xfrm_policy_afinfo_lock);

	spin_lock(&xfrm_policy_afinfo_lock);

	if (likely(xfrm_policy_afinfo[afinfo->family] != NULL)) {

		if (unlikely(xfrm_policy_afinfo[afinfo->family] != afinfo))

			err = -EINVAL;

		else {

			struct dst_ops *dst_ops = afinfo->dst_ops;

			rcu_assign_pointer(xfrm_policy_afinfo[afinfo->family],

		else

			RCU_INIT_POINTER(xfrm_policy_afinfo[afinfo->family],

					 NULL);

	}

	spin_unlock(&xfrm_policy_afinfo_lock);

	if (!err) {

		struct dst_ops *dst_ops = afinfo->dst_ops;



		synchronize_rcu();



		dst_ops->kmem_cachep = NULL;

		dst_ops->check = NULL;

		dst_ops->negative_advice = NULL;

		dst_ops->link_failure = NULL;

		afinfo->garbage_collect = NULL;

	}

	}

	spin_unlock_bh(&xfrm_policy_afinfo_lock);

	synchronize_rcu();

	return err;

}

EXPORT_SYMBOL(xfrm_policy_unregister_afinfo);
@@ -2502,32 +2521,15 @@ static void __net_init xfrm_dst_ops_init(struct net *net) 
{

	struct xfrm_policy_afinfo *afinfo;



	rcu_read_lock_bh();

	afinfo = rcu_dereference_bh(xfrm_policy_afinfo[AF_INET]);

	rcu_read_lock();

	afinfo = rcu_dereference(xfrm_policy_afinfo[AF_INET]);

	if (afinfo)

		net->xfrm.xfrm4_dst_ops = *afinfo->dst_ops;

#if IS_ENABLED(CONFIG_IPV6)

	afinfo = rcu_dereference_bh(xfrm_policy_afinfo[AF_INET6]);

	afinfo = rcu_dereference(xfrm_policy_afinfo[AF_INET6]);

	if (afinfo)

		net->xfrm.xfrm6_dst_ops = *afinfo->dst_ops;

#endif

	rcu_read_unlock_bh();

}



static struct xfrm_policy_afinfo *xfrm_policy_get_afinfo(unsigned short family)

{

	struct xfrm_policy_afinfo *afinfo;

	if (unlikely(family >= NPROTO))

		return NULL;

	rcu_read_lock();

	afinfo = rcu_dereference(xfrm_policy_afinfo[family]);

	if (unlikely(!afinfo))

		rcu_read_unlock();

	return afinfo;

}



static inline void xfrm_policy_put_afinfo(struct xfrm_policy_afinfo *afinfo)

{

	rcu_read_unlock();

}