xfs: check attribute name validity

Check extended attribute entry names for invalid characters.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>

fs/xfs/libxfs/xfs_attr.c

@@ -1336,3 +1336,20 @@ xfs_attr_node_get(xfs_da_args_t *args)
 	xfs_da_state_free(state);
 	return retval;
 }
+
+/* Returns true if the attribute entry name is valid. */
+bool
+xfs_attr_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 nulls here */
+	return !memchr(name, 0, length);
+}

fs/xfs/libxfs/xfs_attr.h

@@ -145,6 +145,6 @@ int xfs_attr_remove(struct xfs_inode *dp, const unsigned char *name, int flags);
 int xfs_attr_remove_args(struct xfs_da_args *args);
 int xfs_attr_list(struct xfs_inode *dp, char *buffer, int bufsize,
 		  int flags, struct attrlist_cursor_kern *cursor);
-
+bool xfs_attr_namecheck(const void *name, size_t length);
 
 #endif	/* __XFS_ATTR_H__ */

fs/xfs/scrub/attr.c

@@ -93,6 +93,12 @@ xchk_xattr_listent(
 		return;
 	}
 
+	/* Does this name make sense? */
+	if (!xfs_attr_namecheck(name, namelen)) {
+		xchk_fblock_set_corrupt(sx->sc, XFS_ATTR_FORK, args.blkno);
+		return;
+	}
+
 	args.flags = ATTR_KERNOTIME;
 	if (flags & XFS_ATTR_ROOT)
 		args.flags |= ATTR_ROOT;