netdev - [PATCH 1/2] neigh: only allow init_net to change the default neigh

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Message-Id: <1371011651-30894-1-git-send-email-gaofeng@cn.fujitsu.com>
Date:	Wed, 12 Jun 2013 12:34:10 +0800
From:	Gao feng <gaofeng@...fujitsu.com>
To:	davem@...emloft.net
Cc:	ebiederm@...ssion.com, netdev@...r.kernel.org,
	Gao feng <gaofeng@...key.lan>,
	Gao feng <gaofeng@...fujitsu.com>
Subject: [PATCH 1/2] neigh: only allow init_net to change the default neigh_parms

From: Gao feng <gaofeng@...key.lan>

Though we don't export the /proc/sys/net/ipv[4,6]/neigh/default/
directory to the un-init_net, but we can still use cmd such as
"ip ntable change name arp_cache locktime 129" to change the locktime
of default neigh_parms.

This patch disallows the un-init_net to find out the neigh_table.parms.
So the un-init_net will failed to influence the init_net.

Signed-off-by: Gao feng <gaofeng@...fujitsu.com>
---
 net/core/neighbour.c | 25 ++++++++++++++-----------
 1 file changed, 14 insertions(+), 11 deletions(-)

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 5c56b21..e4027ff 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -1418,26 +1418,29 @@ static inline struct neigh_parms *lookup_neigh_parms(struct neigh_table *tbl,
 	struct neigh_parms *p;
 
 	for (p = &tbl->parms; p; p = p->next) {
-		if ((p->dev && p->dev->ifindex == ifindex && net_eq(neigh_parms_net(p), net)) ||
-		    (!p->dev && !ifindex))
+		if (p->dev && p->dev->ifindex == ifindex &&
+		    net_eq(neigh_parms_net(p), net))
 			return p;
+
+		if (!p->dev && !ifindex) {
+			if (net_eq(net, &init_net))
+				return p;
+			else
+				return ERR_PTR(-EPERM);
+		}
 	}
 
-	return NULL;
+	return ERR_PTR(-ENOENT);
 }
 
 struct neigh_parms *neigh_parms_alloc(struct net_device *dev,
 				      struct neigh_table *tbl)
 {
-	struct neigh_parms *p, *ref;
+	struct neigh_parms *p;
 	struct net *net = dev_net(dev);
 	const struct net_device_ops *ops = dev->netdev_ops;
 
-	ref = lookup_neigh_parms(tbl, net, 0);
-	if (!ref)
-		return NULL;
-
-	p = kmemdup(ref, sizeof(*p), GFP_KERNEL);
+	p = kmemdup(&tbl->parms, sizeof(*p), GFP_KERNEL);
 	if (p) {
 		p->tbl		  = tbl;
 		atomic_set(&p->refcnt, 1);
@@ -1999,8 +2002,8 @@ static int neightbl_set(struct sk_buff *skb, struct nlmsghdr *nlh)
 			ifindex = nla_get_u32(tbp[NDTPA_IFINDEX]);
 
 		p = lookup_neigh_parms(tbl, net, ifindex);
-		if (p == NULL) {
-			err = -ENOENT;
+		if (IS_ERR(p)) {
+			err = PTR_ERR(p);
 			goto errout_tbl_lock;
 		}
 
-- 
1.8.1.4

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