socket: Unify getsockname and getpeername implementation

They are already implemented by the same get_name hook in the protocol
level. Bring the unification one level up to reduce code duplication
in preparation to supporting these as io_uring operations.

Reviewed-by: Kuniyuki Iwashima <[e-mail]>
Signed-off-by: Gabriel Krisman Bertazi <[e-mail]>
Signed-off-by: Jens Axboe <[e-mail]>

include/linux/socket.h

···
 extern int __sys_listen(int fd, int backlog);
 extern int __sys_listen_socket(struct socket *sock, int backlog);
 extern int __sys_getsockname(int fd, struct sockaddr __user *usockaddr,
-			     int __user *usockaddr_len);
-extern int __sys_getpeername(int fd, struct sockaddr __user *usockaddr,
-			     int __user *usockaddr_len);
+			     int __user *usockaddr_len, int peer);
 extern int __sys_socketpair(int family, int type, int protocol,
 			    int __user *usockvec);
 extern int __sys_shutdown_sock(struct socket *sock, int how);

net/compat.c

···
 		ret = __sys_accept4(a0, compat_ptr(a1), compat_ptr(a[2]), 0);
 		break;
 	case SYS_GETSOCKNAME:
-		ret = __sys_getsockname(a0, compat_ptr(a1), compat_ptr(a[2]));
+		ret = __sys_getsockname(a0, compat_ptr(a1), compat_ptr(a[2]), 0);
 		break;
 	case SYS_GETPEERNAME:
-		ret = __sys_getpeername(a0, compat_ptr(a1), compat_ptr(a[2]));
+		ret = __sys_getsockname(a0, compat_ptr(a1), compat_ptr(a[2]), 1);
 		break;
 	case SYS_SOCKETPAIR:
 		ret = __sys_socketpair(a0, a1, a[2], compat_ptr(a[3]));

net/socket.c

···
 }
 
 /*
- *	Get the local address ('name') of a socket object. Move the obtained
- *	name to user space.
+ *	Get the remote or local address ('name') of a socket object. Move the
+ *	obtained name to user space.
  */
-
 int __sys_getsockname(int fd, struct sockaddr __user *usockaddr,
-		      int __user *usockaddr_len)
+		      int __user *usockaddr_len, int peer)
 {
 	struct socket *sock;
 	struct sockaddr_storage address;
···
 	if (unlikely(!sock))
 		return -ENOTSOCK;
 
-	err = security_socket_getsockname(sock);
+	if (peer)
+		err = security_socket_getpeername(sock);
+	else
+		err = security_socket_getsockname(sock);
 	if (err)
 		return err;
 
-	err = READ_ONCE(sock->ops)->getname(sock, (struct sockaddr *)&address, 0);
+	err = READ_ONCE(sock->ops)->getname(sock, (struct sockaddr *)&address, peer);
 	if (err < 0)
 		return err;
 
···
 SYSCALL_DEFINE3(getsockname, int, fd, struct sockaddr __user *, usockaddr,
 		int __user *, usockaddr_len)
 {
-	return __sys_getsockname(fd, usockaddr, usockaddr_len);
-}
-
-/*
- *	Get the remote address ('name') of a socket object. Move the obtained
- *	name to user space.
- */
-
-int __sys_getpeername(int fd, struct sockaddr __user *usockaddr,
-		      int __user *usockaddr_len)
-{
-	struct socket *sock;
-	struct sockaddr_storage address;
-	CLASS(fd, f)(fd);
-	int err;
-
-	if (fd_empty(f))
-		return -EBADF;
-	sock = sock_from_file(fd_file(f));
-	if (unlikely(!sock))
-		return -ENOTSOCK;
-
-	err = security_socket_getpeername(sock);
-	if (err)
-		return err;
-
-	err = READ_ONCE(sock->ops)->getname(sock, (struct sockaddr *)&address, 1);
-	if (err < 0)
-		return err;
-
-	/* "err" is actually length in this case */
-	return move_addr_to_user(&address, err, usockaddr, usockaddr_len);
+	return __sys_getsockname(fd, usockaddr, usockaddr_len, 0);
 }
 
 SYSCALL_DEFINE3(getpeername, int, fd, struct sockaddr __user *, usockaddr,
 		int __user *, usockaddr_len)
 {
-	return __sys_getpeername(fd, usockaddr, usockaddr_len);
+	return __sys_getsockname(fd, usockaddr, usockaddr_len, 1);
 }
 
 /*
···
 	case SYS_GETSOCKNAME:
 		err =
 		    __sys_getsockname(a0, (struct sockaddr __user *)a1,
-				      (int __user *)a[2]);
+				      (int __user *)a[2], 0);
 		break;
 	case SYS_GETPEERNAME:
 		err =
-		    __sys_getpeername(a0, (struct sockaddr __user *)a1,
-				      (int __user *)a[2]);
+		    __sys_getsockname(a0, (struct sockaddr __user *)a1,
+				      (int __user *)a[2], 1);
 		break;
 	case SYS_SOCKETPAIR:
 		err = __sys_socketpair(a0, a1, a[2], (int __user *)a[3]);