don't bother with path_get()/path_put() in unix_open_file()

Once unix_sock ->path is set, we are guaranteed that its ->path will remain
unchanged (and pinned) until the socket is closed.  OTOH, dentry_open()
does not modify the path passed to it.

IOW, there's no need to copy unix_sk(sk)->path in unix_open_file() - we
can just pass it to dentry_open() and be done with that.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Link: https://lore.kernel.org/20250712054157.GZ1880847@ZenIV
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: Al Viro

net/unix/af_unix.c

@@ -3201,7 +3201,6 @@ EXPORT_SYMBOL_GPL(unix_outq_len);
 
 static int unix_open_file(struct sock *sk)
 {
-	struct path path;
 	struct file *f;
 	int fd;
 
@@ -3211,27 +3210,20 @@ static int unix_open_file(struct sock *sk)
 	if (!smp_load_acquire(&unix_sk(sk)->addr))
 		return -ENOENT;
 
-	path = unix_sk(sk)->path;
-	if (!path.dentry)
+	if (!unix_sk(sk)->path.dentry)
 		return -ENOENT;
 
-	path_get(&path);
-
 	fd = get_unused_fd_flags(O_CLOEXEC);
 	if (fd < 0)
-		goto out;
+		return fd;
 
-	f = dentry_open(&path, O_PATH, current_cred());
+	f = dentry_open(&unix_sk(sk)->path, O_PATH, current_cred());
 	if (IS_ERR(f)) {
 		put_unused_fd(fd);
-		fd = PTR_ERR(f);
-		goto out;
+		return PTR_ERR(f);
 	}
 
 	fd_install(fd, f);
-out:
-	path_put(&path);
-
 	return fd;
 }