Commit 21ee543e authored by Michal Kubecek's avatar Michal Kubecek Committed by David S. Miller
Browse files

xfrm: fix race between netns cleanup and state expire notification 



The xfrm_user module registers its pernet init/exit after xfrm
itself so that its net exit function xfrm_user_net_exit() is
executed before xfrm_net_exit() which calls xfrm_state_fini() to
cleanup the SA's (xfrm states). This opens a window between
zeroing net->xfrm.nlsk pointer and deleting all xfrm_state
instances which may access it (via the timer). If an xfrm state
expires in this window, xfrm_exp_state_notify() will pass null
pointer as socket to nlmsg_multicast().

As the notifications are called inside rcu_read_lock() block, it
is sufficient to retrieve the nlsk socket with rcu_dereference()
and check the it for null.

Signed-off-by: default avatarMichal Kubecek <mkubecek@suse.cz>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 1299b3c4

net/xfrm/xfrm_user.c

+25 −11
Original line number Diff line number Diff line
@@ -955,6 +955,20 @@ static struct sk_buff *xfrm_state_netlink(struct sk_buff *in_skb, 
	return skb;

}



/* A wrapper for nlmsg_multicast() checking that nlsk is still available.

 * Must be called with RCU read lock.

 */

static inline int xfrm_nlmsg_multicast(struct net *net, struct sk_buff *skb,

				       u32 pid, unsigned int group)

{

	struct sock *nlsk = rcu_dereference(net->xfrm.nlsk);



	if (nlsk)

		return nlmsg_multicast(nlsk, skb, pid, group, GFP_ATOMIC);

	else

		return -1;

}



static inline size_t xfrm_spdinfo_msgsize(void)

{

	return NLMSG_ALIGN(4)
@@ -2265,7 +2279,7 @@ static int xfrm_send_migrate(const struct xfrm_selector *sel, u8 dir, u8 type, 
	if (build_migrate(skb, m, num_migrate, k, sel, dir, type) < 0)

		BUG();



	return nlmsg_multicast(net->xfrm.nlsk, skb, 0, XFRMNLGRP_MIGRATE, GFP_ATOMIC);

	return xfrm_nlmsg_multicast(net, skb, 0, XFRMNLGRP_MIGRATE);

}

#else

static int xfrm_send_migrate(const struct xfrm_selector *sel, u8 dir, u8 type,
@@ -2456,7 +2470,7 @@ static int xfrm_exp_state_notify(struct xfrm_state *x, const struct km_event *c) 
		return -EMSGSIZE;

	}



	return nlmsg_multicast(net->xfrm.nlsk, skb, 0, XFRMNLGRP_EXPIRE, GFP_ATOMIC);

	return xfrm_nlmsg_multicast(net, skb, 0, XFRMNLGRP_EXPIRE);

}



static int xfrm_aevent_state_notify(struct xfrm_state *x, const struct km_event *c)
@@ -2471,7 +2485,7 @@ static int xfrm_aevent_state_notify(struct xfrm_state *x, const struct km_event 
	if (build_aevent(skb, x, c) < 0)

		BUG();



	return nlmsg_multicast(net->xfrm.nlsk, skb, 0, XFRMNLGRP_AEVENTS, GFP_ATOMIC);

	return xfrm_nlmsg_multicast(net, skb, 0, XFRMNLGRP_AEVENTS);

}



static int xfrm_notify_sa_flush(const struct km_event *c)
@@ -2497,7 +2511,7 @@ static int xfrm_notify_sa_flush(const struct km_event *c) 


	nlmsg_end(skb, nlh);



	return nlmsg_multicast(net->xfrm.nlsk, skb, 0, XFRMNLGRP_SA, GFP_ATOMIC);

	return xfrm_nlmsg_multicast(net, skb, 0, XFRMNLGRP_SA);

}



static inline size_t xfrm_sa_len(struct xfrm_state *x)
@@ -2584,7 +2598,7 @@ static int xfrm_notify_sa(struct xfrm_state *x, const struct km_event *c) 


	nlmsg_end(skb, nlh);



	return nlmsg_multicast(net->xfrm.nlsk, skb, 0, XFRMNLGRP_SA, GFP_ATOMIC);

	return xfrm_nlmsg_multicast(net, skb, 0, XFRMNLGRP_SA);



out_free_skb:

	kfree_skb(skb);
@@ -2675,7 +2689,7 @@ static int xfrm_send_acquire(struct xfrm_state *x, struct xfrm_tmpl *xt, 
	if (build_acquire(skb, x, xt, xp) < 0)

		BUG();



	return nlmsg_multicast(net->xfrm.nlsk, skb, 0, XFRMNLGRP_ACQUIRE, GFP_ATOMIC);

	return xfrm_nlmsg_multicast(net, skb, 0, XFRMNLGRP_ACQUIRE);

}



/* User gives us xfrm_user_policy_info followed by an array of 0
@@ -2789,7 +2803,7 @@ static int xfrm_exp_policy_notify(struct xfrm_policy *xp, int dir, const struct 
	if (build_polexpire(skb, xp, dir, c) < 0)

		BUG();



	return nlmsg_multicast(net->xfrm.nlsk, skb, 0, XFRMNLGRP_EXPIRE, GFP_ATOMIC);

	return xfrm_nlmsg_multicast(net, skb, 0, XFRMNLGRP_EXPIRE);

}



static int xfrm_notify_policy(struct xfrm_policy *xp, int dir, const struct km_event *c)
@@ -2851,7 +2865,7 @@ static int xfrm_notify_policy(struct xfrm_policy *xp, int dir, const struct km_e 


	nlmsg_end(skb, nlh);



	return nlmsg_multicast(net->xfrm.nlsk, skb, 0, XFRMNLGRP_POLICY, GFP_ATOMIC);

	return xfrm_nlmsg_multicast(net, skb, 0, XFRMNLGRP_POLICY);



out_free_skb:

	kfree_skb(skb);
@@ -2879,7 +2893,7 @@ static int xfrm_notify_policy_flush(const struct km_event *c) 


	nlmsg_end(skb, nlh);



	return nlmsg_multicast(net->xfrm.nlsk, skb, 0, XFRMNLGRP_POLICY, GFP_ATOMIC);

	return xfrm_nlmsg_multicast(net, skb, 0, XFRMNLGRP_POLICY);



out_free_skb:

	kfree_skb(skb);
@@ -2948,7 +2962,7 @@ static int xfrm_send_report(struct net *net, u8 proto, 
	if (build_report(skb, proto, sel, addr) < 0)

		BUG();



	return nlmsg_multicast(net->xfrm.nlsk, skb, 0, XFRMNLGRP_REPORT, GFP_ATOMIC);

	return xfrm_nlmsg_multicast(net, skb, 0, XFRMNLGRP_REPORT);

}



static inline size_t xfrm_mapping_msgsize(void)
@@ -3000,7 +3014,7 @@ static int xfrm_send_mapping(struct xfrm_state *x, xfrm_address_t *ipaddr, 
	if (build_mapping(skb, x, ipaddr, sport) < 0)

		BUG();



	return nlmsg_multicast(net->xfrm.nlsk, skb, 0, XFRMNLGRP_MAPPING, GFP_ATOMIC);

	return xfrm_nlmsg_multicast(net, skb, 0, XFRMNLGRP_MAPPING);

}



static bool xfrm_is_alive(const struct km_event *c)

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