fuse: readdir: check for slash in names

commit efeb9e60 upstream.

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 <mszeredi@suse.cz>
[bwh: Backported to 3.2: drop changes to parse_dirplusfile() which we
 don't have]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

fs/fuse/dir.c

@@ -1063,6 +1063,8 @@ static int parse_dirfile(char *buf, size_t nbytes, struct file *file,
 			return -EIO;
 		if (reclen > nbytes)
 			break;
+		if (memchr(dirent->name, '/', dirent->namelen) != NULL)
+			return -EIO;
 
 		over = filldir(dstbuf, dirent->name, dirent->namelen,
 			       file->f_pos, dirent->ino, dirent->type);