Allow passing O_PATH descriptors via SCM_RIGHTS datagrams

Just need to make sure that AF_UNIX garbage collector won't
confuse O_PATHed socket on filesystem for real AF_UNIX opened
socket.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/file_table.c

@@ -305,6 +305,8 @@ struct file *fget_raw(unsigned int fd)
 	return file;
 }
 
+EXPORT_SYMBOL(fget_raw);
+
 /*
  * Lightweight file lookup - no refcnt increment if fd table isn't shared.
  *

net/core/scm.c

@@ -95,7 +95,7 @@ static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp)
 		int fd = fdp[i];
 		struct file *file;
 
-		if (fd < 0 || !(file = fget(fd)))
+		if (fd < 0 || !(file = fget_raw(fd)))
 			return -EBADF;
 		*fpp++ = file;
 		fpl->count++;

net/unix/garbage.c

@@ -104,7 +104,7 @@ struct sock *unix_get_socket(struct file *filp)
 	/*
 	 *	Socket ?
 	 */
-	if (S_ISSOCK(inode->i_mode)) {
+	if (S_ISSOCK(inode->i_mode) && !(filp->f_mode & FMODE_PATH)) {
 		struct socket *sock = SOCKET_I(inode);
 		struct sock *s = sock->sk;