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xfrm: policy: add sequence count to sync with hash resize 

Once xfrm_policy_lookup_bytype doesn't grab xfrm_policy_lock anymore its
possible for a hash resize to occur in parallel.

Use sequence counter to block lookup in case a resize is in
progress and to also re-lookup in case hash table was altered
in the mean time (might cause use to not find the best-match).

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 15:17:54 +02:00 committed by Steffen Klassert
parent e1e551bc56
commit 30846090a7
1 changed files with 19 additions and 2 deletions
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21
net/xfrm/xfrm_policy.c
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@ -49,6 +49,7 @@ static struct xfrm_policy_afinfo __rcu *xfrm_policy_afinfo[NPROTO]
__read_mostly;
static struct kmem_cache *xfrm_dst_cache __read_mostly;
static __read_mostly seqcount_t xfrm_policy_hash_generation;
static void xfrm_init_pmtu(struct dst_entry *dst);
static int stale_bundle(struct dst_entry *dst);
@ -479,6 +480,10 @@ static void xfrm_bydst_resize(struct net *net, int dir)
return;
write_lock_bh(&net->xfrm.xfrm_policy_lock);
write_seqcount_begin(&xfrm_policy_hash_generation);
odst = rcu_dereference_protected(net->xfrm.policy_bydst[dir].table,
lockdep_is_held(&net->xfrm.xfrm_policy_lock));
odst = rcu_dereference_protected(net->xfrm.policy_bydst[dir].table,
lockdep_is_held(&net->xfrm.xfrm_policy_lock));
@ -489,6 +494,7 @@ static void xfrm_bydst_resize(struct net *net, int dir)
rcu_assign_pointer(net->xfrm.policy_bydst[dir].table, ndst);
net->xfrm.policy_bydst[dir].hmask = nhashmask;
write_seqcount_end(&xfrm_policy_hash_generation);
write_unlock_bh(&net->xfrm.xfrm_policy_lock);
synchronize_rcu();
@ -1104,7 +1110,8 @@ static struct xfrm_policy *xfrm_policy_lookup_bytype(struct net *net, u8 type,
struct xfrm_policy *pol, *ret;
const xfrm_address_t *daddr, *saddr;
struct hlist_head *chain;
u32 priority = ~0U;
unsigned int sequence;
u32 priority;
daddr = xfrm_flowi_daddr(fl, family);
saddr = xfrm_flowi_saddr(fl, family);
@ -1112,7 +1119,13 @@ static struct xfrm_policy *xfrm_policy_lookup_bytype(struct net *net, u8 type,
return NULL;
read_lock_bh(&net->xfrm.xfrm_policy_lock);
chain = policy_hash_direct(net, daddr, saddr, family, dir);
retry:
do {
sequence = read_seqcount_begin(&xfrm_policy_hash_generation);
chain = policy_hash_direct(net, daddr, saddr, family, dir);
} while (read_seqcount_retry(&xfrm_policy_hash_generation, sequence));
priority = ~0U;
ret = NULL;
hlist_for_each_entry_rcu(pol, chain, bydst) {
err = xfrm_policy_match(pol, fl, type, family, dir);
@ -1148,6 +1161,9 @@ 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);
fail:
read_unlock_bh(&net->xfrm.xfrm_policy_lock);
@ -3090,6 +3106,7 @@ static struct pernet_operations __net_initdata xfrm_net_ops = {
void __init xfrm_init(void)
{
register_pernet_subsys(&xfrm_net_ops);
seqcount_init(&xfrm_policy_hash_generation);
xfrm_input_init();
}