xfs: check directory name validity

Check directory entry names for invalid characters.

Signed-off-by: Darrick J. Wong <[e-mail]>
Reviewed-by: Brian Foster <[e-mail]>

fs/xfs/libxfs/xfs_dir2.c

···
 	xfs_trans_log_inode(tp, dp, XFS_ILOG_CORE);
 	return 0;
 }
+
+/* Returns true if the directory entry name is valid. */
+bool
+xfs_dir2_namecheck(
+	const void	*name,
+	size_t		length)
+{
+	/*
+	 * MAXNAMELEN includes the trailing null, but (name/length) leave it
+	 * out, so use >= for the length check.
+	 */
+	if (length >= MAXNAMELEN)
+		return false;
+
+	/* There shouldn't be any slashes or nulls here */
+	return !memchr(name, '/', length) && !memchr(name, 0, length);
+}

fs/xfs/libxfs/xfs_dir2.h

···
 unsigned char xfs_dir3_get_dtype(struct xfs_mount *mp, uint8_t filetype);
 void *xfs_dir3_data_endp(struct xfs_da_geometry *geo,
 		struct xfs_dir2_data_hdr *hdr);
+bool xfs_dir2_namecheck(const void *name, size_t length);
 
 #endif	/* __XFS_DIR2_H__ */

fs/xfs/scrub/dir.c

···
 		goto out;
 	}
 
+	/* Does this name make sense? */
+	if (!xfs_dir2_namecheck(name, namelen)) {
+		xchk_fblock_set_corrupt(sdc->sc, XFS_DATA_FORK, offset);
+		goto out;
+	}
+
 	if (!strncmp(".", name, namelen)) {
 		/* If this is "." then check that the inum matches the dir. */
 		if (xfs_sb_version_hasftype(&mp->m_sb) && type != DT_DIR)