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Commit b65e3d7b authored by Florian Westphal's avatar Florian Westphal Committed by Steffen Klassert
Browse files

xfrm: state: add sequence count to detect hash resizes 



Once xfrm_state_find is lockless we have to cope with a concurrent
resize opertion.

We use a sequence counter to block in case a resize is in progress
and to detect if we might have missed a state that got moved to
a new hash table.

Signed-off-by: default avatarFlorian Westphal <fw@strlen.de>
Signed-off-by: default avatarSteffen Klassert <steffen.klassert@secunet.com>
parent df7274eb

net/xfrm/xfrm_state.c

+15 −0
Original line number Diff line number Diff line
@@ -36,6 +36,7 @@ 
 */



static unsigned int xfrm_state_hashmax __read_mostly = 1 * 1024 * 1024;

static __read_mostly seqcount_t xfrm_state_hash_generation = SEQCNT_ZERO(xfrm_state_hash_generation);



static inline bool xfrm_state_hold_rcu(struct xfrm_state __rcu *x)

{
@@ -127,6 +128,7 @@ static void xfrm_hash_resize(struct work_struct *work) 
	}



	spin_lock_bh(&net->xfrm.xfrm_state_lock);

	write_seqcount_begin(&xfrm_state_hash_generation);



	nhashmask = (nsize / sizeof(struct hlist_head)) - 1U;

	for (i = net->xfrm.state_hmask; i >= 0; i--)
@@ -143,6 +145,7 @@ static void xfrm_hash_resize(struct work_struct *work) 
	net->xfrm.state_byspi = nspi;

	net->xfrm.state_hmask = nhashmask;



	write_seqcount_end(&xfrm_state_hash_generation);

	spin_unlock_bh(&net->xfrm.xfrm_state_lock);



	osize = (ohashmask + 1) * sizeof(struct hlist_head);
@@ -787,10 +790,13 @@ xfrm_state_find(const xfrm_address_t *daddr, const xfrm_address_t *saddr, 
	struct xfrm_state *best = NULL;

	u32 mark = pol->mark.v & pol->mark.m;

	unsigned short encap_family = tmpl->encap_family;

	unsigned int sequence;

	struct km_event c;



	to_put = NULL;



	sequence = read_seqcount_begin(&xfrm_state_hash_generation);



	spin_lock_bh(&net->xfrm.xfrm_state_lock);

	h = xfrm_dst_hash(net, daddr, saddr, tmpl->reqid, encap_family);

	hlist_for_each_entry_rcu(x, net->xfrm.state_bydst + h, bydst) {
@@ -894,6 +900,15 @@ xfrm_state_find(const xfrm_address_t *daddr, const xfrm_address_t *saddr, 
	spin_unlock_bh(&net->xfrm.xfrm_state_lock);

	if (to_put)

		xfrm_state_put(to_put);



	if (read_seqcount_retry(&xfrm_state_hash_generation, sequence)) {

		*err = -EAGAIN;

		if (x) {

			xfrm_state_put(x);

			x = NULL;

		}

	}



	return x;

}