fuse: readdir: check for slash in names

Userspace can add names containing a slash character to the directory
listing. Don't allow this as it could cause all sorts of trouble.

Signed-off-by: Miklos Szeredi <[e-mail]>
Cc: [e-mail]

fs/fuse/dir.c

···
 			return -EIO;
 		if (reclen > nbytes)
 			break;
+		if (memchr(dirent->name, '/', dirent->namelen) != NULL)
+			return -EIO;
 
 		if (!dir_emit(ctx, dirent->name, dirent->namelen,
 			       dirent->ino, dirent->type))
···
 			return -EIO;
 		if (reclen > nbytes)
 			break;
+		if (memchr(dirent->name, '/', dirent->namelen) != NULL)
+			return -EIO;
 
 		if (!over) {
 			/* We fill entries into dstbuf only as much as