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Message-ID: <20240611222905.34695-12-kuniyu@amazon.com>
Date: Tue, 11 Jun 2024 15:29:05 -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 v2 net-next 11/11] af_unix: Don't use spin_lock_nested() in copy_peercred().
When (AF_UNIX, SOCK_STREAM) socket connect()s to a listening socket,
the listener's sk_peer_pid/sk_peer_cred are copied to the client in
copy_peercred().
Then, two sk_peer_locks are held there; one is client's and another
is listener's.
However, the latter is not needed because we hold the listner's
unix_state_lock() there and unix_listen() cannot update the cred
concurrently.
Let's drop the unnecessary spin_lock() and use the bare spin_lock()
for the client to protect concurrent read by getsockopt(SO_PEERCRED).
Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
---
net/unix/af_unix.c | 13 +++----------
1 file changed, 3 insertions(+), 10 deletions(-)
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 64bfd25a6b31..1309f0beacf0 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -757,19 +757,12 @@ static void update_peercred(struct sock *sk)
static void copy_peercred(struct sock *sk, struct sock *peersk)
{
- if (sk < peersk) {
- spin_lock(&sk->sk_peer_lock);
- spin_lock_nested(&peersk->sk_peer_lock, SINGLE_DEPTH_NESTING);
- } else {
- spin_lock(&peersk->sk_peer_lock);
- spin_lock_nested(&sk->sk_peer_lock, SINGLE_DEPTH_NESTING);
- }
+ lockdep_assert_held(&unix_sk(peersk)->lock);
- sk->sk_peer_pid = get_pid(peersk->sk_peer_pid);
+ spin_lock(&sk->sk_peer_lock);
+ sk->sk_peer_pid = get_pid(peersk->sk_peer_pid);
sk->sk_peer_cred = get_cred(peersk->sk_peer_cred);
-
spin_unlock(&sk->sk_peer_lock);
- spin_unlock(&peersk->sk_peer_lock);
}
static int unix_listen(struct socket *sock, int backlog)
--
2.30.2
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