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af_unix: Don't use spin_lock_nested() in copy_peercred().

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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@amazon.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Kuniyuki Iwashima 2024-06-20 13:56:23 -07:00 committed by Paolo Abeni
parent e4bd881d98
commit 22e5751b05
1 changed files with 3 additions and 10 deletions
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13
net/unix/af_unix.c
View file

@ -772,19 +772,12 @@ 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)