Revert "xfrm: policy: Read seqcount outside of rcu-read side in xfrm_policy_lookup_by...

This reverts commit d7b0408934c749f546b01f2b33d07421a49b6f3e.

This commit tried to fix a locking bug introduced by commit 77cc278f7b20
("xfrm: policy: Use sequence counters with associated lock"). As it
turned out, this patch did not really fix the bug. A proper fix
for this bug is applied on top of this revert.

Signed-off-by: Steffen Klassert <[email protected]>

diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index e9d0df2a2ab1722a3301414069252a2c9ecaa69a..ce500f847b99118b1ee50afcfa101856943d2d91 100644 (file)
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -2092,15 +2092,12 @@ static struct xfrm_policy *xfrm_policy_lookup_bytype(struct net *net, u8 type,
        if (unlikely(!daddr || !saddr))
                return NULL;
 
- retry:
-       sequence = read_seqcount_begin(&xfrm_policy_hash_generation);
        rcu_read_lock();
-
-       chain = policy_hash_direct(net, daddr, saddr, family, dir);
-       if (read_seqcount_retry(&xfrm_policy_hash_generation, sequence)) {
-               rcu_read_unlock();
-               goto retry;
-       }
+ 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));
 
        ret = NULL;
        hlist_for_each_entry_rcu(pol, chain, bydst) {
@@ -2131,15 +2128,11 @@ static struct xfrm_policy *xfrm_policy_lookup_bytype(struct net *net, u8 type,
        }
 
 skip_inexact:
-       if (read_seqcount_retry(&xfrm_policy_hash_generation, sequence)) {
-               rcu_read_unlock();
+       if (read_seqcount_retry(&xfrm_policy_hash_generation, sequence))
                goto retry;
-       }
 
-       if (ret && !xfrm_pol_hold_rcu(ret)) {
-               rcu_read_unlock();
+       if (ret && !xfrm_pol_hold_rcu(ret))
                goto retry;
-       }
 fail:
        rcu_read_unlock();