Commit dd103c9a authored by Kuniyuki Iwashima's avatar Kuniyuki Iwashima Committed by Jakub Kicinski
Browse files

neighbour: Remove __pneigh_lookup(). 



__pneigh_lookup() is the lockless version of pneigh_lookup(),
but its only caller pndisc_is_router() holds the table lock and
reads pneigh_netry.flags.

This is because accessing pneigh_entry after pneigh_lookup() was
illegal unless the caller holds RTNL or the table lock.

Now, pneigh_entry is guaranteed to be alive during the RCU critical
section.

Let's call pneigh_lookup() and use READ_ONCE() for n->flags in
pndisc_is_router() and remove __pneigh_lookup().

Signed-off-by: default avatarKuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250716221221.442239-13-kuniyu@google.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent b9c89fa1

include/net/neighbour.h

+0 −2
Original line number Diff line number Diff line
@@ -381,8 +381,6 @@ void pneigh_enqueue(struct neigh_table *tbl, struct neigh_parms *p, 
		    struct sk_buff *skb);

struct pneigh_entry *pneigh_lookup(struct neigh_table *tbl, struct net *net,

				   const void *key, struct net_device *dev);

struct pneigh_entry *__pneigh_lookup(struct neigh_table *tbl, struct net *net,

				     const void *key, struct net_device *dev);

struct pneigh_entry *pneigh_create(struct neigh_table *tbl, struct net *net,

				   const void *key, struct net_device *dev);

int pneigh_delete(struct neigh_table *tbl, struct net *net, const void *key,

net/core/neighbour.c

+0 −11
Original line number Diff line number Diff line
@@ -737,17 +737,6 @@ static struct pneigh_entry *__pneigh_lookup_1(struct pneigh_entry *n, 
	return NULL;

}



struct pneigh_entry *__pneigh_lookup(struct neigh_table *tbl,

		struct net *net, const void *pkey, struct net_device *dev)

{

	unsigned int key_len = tbl->key_len;

	u32 hash_val = pneigh_hash(pkey, key_len);



	return __pneigh_lookup_1(rcu_dereference_protected(tbl->phash_buckets[hash_val], 1),

				 net, pkey, key_len, dev);

}

EXPORT_SYMBOL_GPL(__pneigh_lookup);



struct pneigh_entry *pneigh_lookup(struct neigh_table *tbl,

				   struct net *net, const void *pkey,

				   struct net_device *dev)

net/ipv6/ndisc.c

+2 −4
Original line number Diff line number Diff line
@@ -768,11 +768,9 @@ static int pndisc_is_router(const void *pkey, 
	struct pneigh_entry *n;

	int ret = -1;



	read_lock_bh(&nd_tbl.lock);

	n = __pneigh_lookup(&nd_tbl, dev_net(dev), pkey, dev);

	n = pneigh_lookup(&nd_tbl, dev_net(dev), pkey, dev);

	if (n)

		ret = !!(n->flags & NTF_ROUTER);

	read_unlock_bh(&nd_tbl.lock);

		ret = !!(READ_ONCE(n->flags) & NTF_ROUTER);



	return ret;

}