netdev - [PATCH v2 net-next 08/15] neighbour: Annotate access to struct pneigh

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Message-ID: <20250712203515.4099110-9-kuniyu@google.com>
Date: Sat, 12 Jul 2025 20:34:17 +0000
From: Kuniyuki Iwashima <kuniyu@...gle.com>
To: "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, David Ahern <dsahern@...nel.org>
Cc: Simon Horman <horms@...nel.org>, Kuniyuki Iwashima <kuniyu@...gle.com>, 
	Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org
Subject: [PATCH v2 net-next 08/15] neighbour: Annotate access to struct pneigh_entry.{flags,protocol}.

We will convert pneigh readers to RCU, and its flags and protocol
will be read locklessly.

Let's annotate the access to the two fields.

Note that all access to pn->permanent is under RTNL (neigh_add()
and pneigh_ifdown_and_unlock()), so WRITE_ONCE() and READ_ONCE()
are not needed.

Signed-off-by: Kuniyuki Iwashima <kuniyu@...gle.com>
---
 net/core/neighbour.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 6f688b643c82b..b8562c6c3e8ef 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -2044,10 +2044,10 @@ static int neigh_add(struct sk_buff *skb, struct nlmsghdr *nlh,
 		err = -ENOBUFS;
 		pn = pneigh_create(tbl, net, dst, dev);
 		if (pn) {
-			pn->flags = ndm_flags;
+			WRITE_ONCE(pn->flags, ndm_flags);
 			pn->permanent = !!(ndm->ndm_state & NUD_PERMANENT);
 			if (protocol)
-				pn->protocol = protocol;
+				WRITE_ONCE(pn->protocol, protocol);
 			err = 0;
 		}
 		goto out;
@@ -2683,8 +2683,9 @@ static int pneigh_fill_info(struct sk_buff *skb, struct pneigh_entry *pn,
 	if (nlh == NULL)
 		return -EMSGSIZE;
 
-	neigh_flags_ext = pn->flags >> NTF_EXT_SHIFT;
-	neigh_flags     = pn->flags & NTF_OLD_MASK;
+	neigh_flags = READ_ONCE(pn->flags);
+	neigh_flags_ext = neigh_flags >> NTF_EXT_SHIFT;
+	neigh_flags &= NTF_OLD_MASK;
 
 	ndm = nlmsg_data(nlh);
 	ndm->ndm_family	 = tbl->family;
@@ -2698,7 +2699,7 @@ static int pneigh_fill_info(struct sk_buff *skb, struct pneigh_entry *pn,
 	if (nla_put(skb, NDA_DST, tbl->key_len, pn->key))
 		goto nla_put_failure;
 
-	if (pn->protocol && nla_put_u8(skb, NDA_PROTOCOL, pn->protocol))
+	if (pn->protocol && nla_put_u8(skb, NDA_PROTOCOL, READ_ONCE(pn->protocol)))
 		goto nla_put_failure;
 	if (neigh_flags_ext && nla_put_u32(skb, NDA_FLAGS_EXT, neigh_flags_ext))
 		goto nla_put_failure;
-- 
2.50.0.727.gbf7dc18ff4-goog