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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: Florian Westphal <fw@strlen.de>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
This commit is contained in:
Florian Westphal 2016-08-11 15:17:55 +02:00 committed by Steffen Klassert
parent 30846090a7
commit e37cc8ade5
1 changed files with 7 additions and 1 deletions
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8
net/xfrm/xfrm_policy.c
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@ -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);