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authorTimo Teräs <timo.teras@iki.fi>2010-03-31 00:17:05 +0000
committerDavid S. Miller <davem@davemloft.net>2010-04-01 19:41:35 -0700
commitea2dea9dacc256fe927857feb423872051642ae7 (patch)
tree507da54eb46680b833ead15c3e74f9312cf10c22 /net/xfrm
parentc8bf4d04f970fafb3430d332533e1cf103f2a018 (diff)
downloadlinux-2.6.34-ux500-ea2dea9dacc256fe927857feb423872051642ae7.tar.gz
xfrm: remove policy lock when accessing policy->walk.dead
All of the code considers ->dead as a hint that the cached policy needs to get refreshed. The read side can just drop the read lock without any side effects. The write side needs to make sure that it's written only exactly once. Only possible race is at xfrm_policy_kill(). This is fixed by checking result of __xfrm_policy_unlink() when needed. It will always succeed if the policy object is looked up from the hash list (so some checks are removed), but it needs to be checked if we are trying to unlink policy via a reference (appropriate checks added). Since policy->walk.dead is written exactly once, it no longer needs to be protected with a write lock. Signed-off-by: Timo Teras <timo.teras@iki.fi> Acked-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/xfrm')
-rw-r--r--net/xfrm/xfrm_policy.c31
-rw-r--r--net/xfrm/xfrm_user.c6
2 files changed, 10 insertions, 27 deletions
diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index 843e066649c..82789cf1c63 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -156,7 +156,7 @@ static void xfrm_policy_timer(unsigned long data)
read_lock(&xp->lock);
- if (xp->walk.dead)
+ if (unlikely(xp->walk.dead))
goto out;
dir = xfrm_policy_id2dir(xp->index);
@@ -297,17 +297,7 @@ static DECLARE_WORK(xfrm_policy_gc_work, xfrm_policy_gc_task);
static void xfrm_policy_kill(struct xfrm_policy *policy)
{
- int dead;
-
- write_lock_bh(&policy->lock);
- dead = policy->walk.dead;
policy->walk.dead = 1;
- write_unlock_bh(&policy->lock);
-
- if (unlikely(dead)) {
- WARN_ON(1);
- return;
- }
spin_lock_bh(&xfrm_policy_gc_lock);
hlist_add_head(&policy->bydst, &xfrm_policy_gc_list);
@@ -776,7 +766,6 @@ xfrm_policy_flush_secctx_check(struct net *net, u8 type, struct xfrm_audit *audi
int xfrm_policy_flush(struct net *net, u8 type, struct xfrm_audit *audit_info)
{
int dir, err = 0, cnt = 0;
- struct xfrm_policy *dp;
write_lock_bh(&xfrm_policy_lock);
@@ -794,10 +783,9 @@ int xfrm_policy_flush(struct net *net, u8 type, struct xfrm_audit *audit_info)
&net->xfrm.policy_inexact[dir], bydst) {
if (pol->type != type)
continue;
- dp = __xfrm_policy_unlink(pol, dir);
+ __xfrm_policy_unlink(pol, dir);
write_unlock_bh(&xfrm_policy_lock);
- if (dp)
- cnt++;
+ cnt++;
xfrm_audit_policy_delete(pol, 1, audit_info->loginuid,
audit_info->sessionid,
@@ -816,10 +804,9 @@ int xfrm_policy_flush(struct net *net, u8 type, struct xfrm_audit *audit_info)
bydst) {
if (pol->type != type)
continue;
- dp = __xfrm_policy_unlink(pol, dir);
+ __xfrm_policy_unlink(pol, dir);
write_unlock_bh(&xfrm_policy_lock);
- if (dp)
- cnt++;
+ cnt++;
xfrm_audit_policy_delete(pol, 1,
audit_info->loginuid,
@@ -1132,6 +1119,9 @@ int xfrm_sk_policy_insert(struct sock *sk, int dir, struct xfrm_policy *pol)
__xfrm_policy_link(pol, XFRM_POLICY_MAX+dir);
}
if (old_pol)
+ /* Unlinking succeeds always. This is the only function
+ * allowed to delete or replace socket policy.
+ */
__xfrm_policy_unlink(old_pol, XFRM_POLICY_MAX+dir);
write_unlock_bh(&xfrm_policy_lock);
@@ -1737,11 +1727,8 @@ restart:
goto error;
}
- for (pi = 0; pi < npols; pi++) {
- read_lock_bh(&pols[pi]->lock);
+ for (pi = 0; pi < npols; pi++)
pol_dead |= pols[pi]->walk.dead;
- read_unlock_bh(&pols[pi]->lock);
- }
write_lock_bh(&policy->lock);
if (unlikely(pol_dead || stale_bundle(dst))) {
diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index da5ba86181d..a267fbdda52 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -1770,13 +1770,9 @@ static int xfrm_add_pol_expire(struct sk_buff *skb, struct nlmsghdr *nlh,
if (xp == NULL)
return -ENOENT;
- read_lock(&xp->lock);
- if (xp->walk.dead) {
- read_unlock(&xp->lock);
+ if (unlikely(xp->walk.dead))
goto out;
- }
- read_unlock(&xp->lock);
err = 0;
if (up->hard) {
uid_t loginuid = NETLINK_CB(skb).loginuid;