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Commit e37cc8ad authored by Florian Westphal's avatar Florian Westphal Committed by Steffen Klassert
Browse files

xfrm: policy: use atomic_inc_not_zero in rcu section 



If we don't hold the policy lock anymore the refcnt might
already be 0, i.e. policy struct is about to be free'd.

Switch to atomic_inc_not_zero to avoid this.

On removal policies are already unlinked from the tables (lists)
before the last _put occurs so we are not supposed to find the same
'dead' entry on the next loop, so its safe to just repeat the lookup.

Signed-off-by: default avatarFlorian Westphal <fw@strlen.de>
Signed-off-by: default avatarSteffen Klassert <steffen.klassert@secunet.com>
parent 30846090

net/xfrm/xfrm_policy.c

+7 −1
Original line number Diff line number Diff line
@@ -60,6 +60,11 @@ static void __xfrm_policy_link(struct xfrm_policy *pol, int dir); 
static struct xfrm_policy *__xfrm_policy_unlink(struct xfrm_policy *pol,

						int dir);



static inline bool xfrm_pol_hold_rcu(struct xfrm_policy *policy)

{

	return atomic_inc_not_zero(&policy->refcnt);

}



static inline bool

__xfrm4_selector_match(const struct xfrm_selector *sel, const struct flowi *fl)

{
@@ -1164,7 +1169,8 @@ static struct xfrm_policy *xfrm_policy_lookup_bytype(struct net *net, u8 type, 
	if (read_seqcount_retry(&xfrm_policy_hash_generation, sequence))

		goto retry;



	xfrm_pol_hold(ret);

	if (ret && !xfrm_pol_hold_rcu(ret))

		goto retry;

fail:

	read_unlock_bh(&net->xfrm.xfrm_policy_lock);