netdev - [PATCH v3 net-next 05/11] af_unix: Don't acquire unix_state_lock() for sock_i

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Date: Fri, 14 Jun 2024 13:07:09 -0700
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
	<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>
CC: Kent Overstreet <kent.overstreet@...ux.dev>, Kuniyuki Iwashima
	<kuniyu@...zon.com>, Kuniyuki Iwashima <kuni1840@...il.com>,
	<netdev@...r.kernel.org>
Subject: [PATCH v3 net-next 05/11] af_unix: Don't acquire unix_state_lock() for sock_i_ino().

sk_diag_dump_peer() and sk_diag_dump() call unix_state_lock() for
sock_i_ino() which reads SOCK_INODE(sk->sk_socket)->i_ino, but it's
protected by sk->sk_callback_lock.

Let's remove unnecessary unix_state_lock().

Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
---
 net/unix/diag.c | 30 ++++++++++--------------------
 1 file changed, 10 insertions(+), 20 deletions(-)

diff --git a/net/unix/diag.c b/net/unix/diag.c
index 937edf4afed4..d2d66727b0da 100644
--- a/net/unix/diag.c
+++ b/net/unix/diag.c
@@ -47,9 +47,7 @@ static int sk_diag_dump_peer(struct sock *sk, struct sk_buff *nlskb)
 
 	peer = unix_peer_get(sk);
 	if (peer) {
-		unix_state_lock(peer);
 		ino = sock_i_ino(peer);
-		unix_state_unlock(peer);
 		sock_put(peer);
 
 		return nla_put_u32(nlskb, UNIX_DIAG_PEER, ino);
@@ -180,22 +178,6 @@ static int sk_diag_fill(struct sock *sk, struct sk_buff *skb, struct unix_diag_r
 	return -EMSGSIZE;
 }
 
-static int sk_diag_dump(struct sock *sk, struct sk_buff *skb, struct unix_diag_req *req,
-			struct user_namespace *user_ns,
-			u32 portid, u32 seq, u32 flags)
-{
-	int sk_ino;
-
-	unix_state_lock(sk);
-	sk_ino = sock_i_ino(sk);
-	unix_state_unlock(sk);
-
-	if (!sk_ino)
-		return 0;
-
-	return sk_diag_fill(sk, skb, req, user_ns, portid, seq, flags, sk_ino);
-}
-
 static int unix_diag_dump(struct sk_buff *skb, struct netlink_callback *cb)
 {
 	struct net *net = sock_net(skb->sk);
@@ -213,14 +195,22 @@ static int unix_diag_dump(struct sk_buff *skb, struct netlink_callback *cb)
 		num = 0;
 		spin_lock(&net->unx.table.locks[slot]);
 		sk_for_each(sk, &net->unx.table.buckets[slot]) {
+			int sk_ino;
+
 			if (num < s_num)
 				goto next;
+
 			if (!(req->udiag_states & (1 << READ_ONCE(sk->sk_state))))
 				goto next;
-			if (sk_diag_dump(sk, skb, req, sk_user_ns(skb->sk),
+
+			sk_ino = sock_i_ino(sk);
+			if (!sk_ino)
+				goto next;
+
+			if (sk_diag_fill(sk, skb, req, sk_user_ns(skb->sk),
 					 NETLINK_CB(cb->skb).portid,
 					 cb->nlh->nlmsg_seq,
-					 NLM_F_MULTI) < 0) {
+					 NLM_F_MULTI, sk_ino) < 0) {
 				spin_unlock(&net->unx.table.locks[slot]);
 				goto done;
 			}
-- 
2.30.2