xfs: attr fork iext must be loaded before calling xfs_attr_is_leaf

Christoph noticed that the xfs_attr_is_leaf in xfs_attr_get_ilocked can
access the incore extent tree of the attr fork, but nothing in the
xfs_attr_get path guarantees that the incore tree is actually loaded.

Most of the time it is, but seeing as xfs_attr_is_leaf ignores the
return value of xfs_iext_get_extent I guess we've been making choices
based on random stack contents and nobody's complained?

Reported-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

1 files changed, 17 insertions, 0 deletions

diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
index f8f7445b063c..54edc690ac1e 100644
--- a/fs/xfs/libxfs/xfs_attr.c
+++ b/fs/xfs/libxfs/xfs_attr.c
@@ -87,6 +87,8 @@ xfs_attr_is_leaf(
 	struct xfs_iext_cursor	icur;
 	struct xfs_bmbt_irec	imap;
 
+	ASSERT(!xfs_need_iread_extents(ifp));
+
 	if (ifp->if_nextents != 1 || ifp->if_format != XFS_DINODE_FMT_EXTENTS)
 		return false;
 
@@ -224,11 +226,21 @@ int
 xfs_attr_get_ilocked(
 	struct xfs_da_args	*args)
 {
+	int			error;
+
 	xfs_assert_ilocked(args->dp, XFS_ILOCK_SHARED | XFS_ILOCK_EXCL);
 
 	if (!xfs_inode_hasattr(args->dp))
 		return -ENOATTR;
 
+	/*
+	 * The incore attr fork iext tree must be loaded for xfs_attr_is_leaf
+	 * to work correctly.
+	 */
+	error = xfs_iread_extents(args->trans, args->dp, XFS_ATTR_FORK);
+	if (error)
+		return error;
+
 	if (args->dp->i_af.if_format == XFS_DINODE_FMT_LOCAL)
 		return xfs_attr_shortform_getvalue(args);
 	if (xfs_attr_is_leaf(args->dp))
@@ -870,6 +882,11 @@ xfs_attr_lookup(
 		return -ENOATTR;
 	}
 
+	/* Prerequisite for xfs_attr_is_leaf */
+	error = xfs_iread_extents(args->trans, args->dp, XFS_ATTR_FORK);
+	if (error)
+		return error;
+
 	if (xfs_attr_is_leaf(dp)) {
 		error = xfs_attr_leaf_hasname(args, &bp);