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neighbour: Remove __pneigh_lookup().

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__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: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250716221221.442239-13-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Kuniyuki Iwashima
2025-07-16 22:08:17 +00:00
committed by Jakub Kicinski
parent b9c89fa128
commit dd103c9a53
3 changed files with 2 additions and 17 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
include/net/neighbour.h
View File

@@ -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,

11
net/core/neighbour.c
View File

@@ -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)

6
net/ipv6/ndisc.c
View File

@@ -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;
}