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>

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);
 

fs/xfs/xfs_attr_item.c

@@ -498,6 +498,25 @@ xfs_attri_validate(
 	return xfs_verify_ino(mp, attrp->alfi_ino);
 }
 
+static int
+xfs_attri_iread_extents(
+	struct xfs_inode		*ip)
+{
+	struct xfs_trans		*tp;
+	int				error;
+
+	error = xfs_trans_alloc_empty(ip->i_mount, &tp);
+	if (error)
+		return error;
+
+	xfs_ilock(ip, XFS_ILOCK_EXCL);
+	error = xfs_iread_extents(tp, ip, XFS_ATTR_FORK);
+	xfs_iunlock(ip, XFS_ILOCK_EXCL);
+	xfs_trans_cancel(tp);
+
+	return error;
+}
+
 static inline struct xfs_attr_intent *
 xfs_attri_recover_work(
 	struct xfs_mount		*mp,
@@ -508,13 +527,22 @@ xfs_attri_recover_work(
 {
 	struct xfs_attr_intent		*attr;
 	struct xfs_da_args		*args;
+	struct xfs_inode		*ip;
 	int				local;
 	int				error;
 
-	error = xlog_recover_iget(mp,  attrp->alfi_ino, ipp);
+	error = xlog_recover_iget(mp,  attrp->alfi_ino, &ip);
 	if (error)
 		return ERR_PTR(error);
 
+	if (xfs_inode_has_attr_fork(ip)) {
+		error = xfs_attri_iread_extents(ip);
+		if (error) {
+			xfs_irele(ip);
+			return ERR_PTR(error);
+		}
+	}
+
 	attr = kzalloc(sizeof(struct xfs_attr_intent) +
 			sizeof(struct xfs_da_args), GFP_KERNEL | __GFP_NOFAIL);
 	args = (struct xfs_da_args *)(attr + 1);
@@ -531,7 +559,7 @@ xfs_attri_recover_work(
 	attr->xattri_nameval = xfs_attri_log_nameval_get(nv);
 	ASSERT(attr->xattri_nameval);
 
-	args->dp = *ipp;
+	args->dp = ip;
 	args->geo = mp->m_attr_geo;
 	args->whichfork = XFS_ATTR_FORK;
 	args->name = nv->name.i_addr;
@@ -561,6 +589,7 @@ xfs_attri_recover_work(
 	}
 
 	xfs_defer_add_item(dfp, &attr->xattri_list);
+	*ipp = ip;
 	return attr;
 }
 
@@ -615,16 +644,17 @@ xfs_attr_recover_work(
 		XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp,
 				&attrip->attri_format,
 				sizeof(attrip->attri_format));
-	if (error) {
-		xfs_trans_cancel(tp);
-		goto out_unlock;
-	}
+	if (error)
+		goto out_cancel;
 
 	error = xfs_defer_ops_capture_and_commit(tp, capture_list);
 out_unlock:
 	xfs_iunlock(ip, XFS_ILOCK_EXCL);
 	xfs_irele(ip);
 	return error;
+out_cancel:
+	xfs_trans_cancel(tp);
+	goto out_unlock;
 }
 
 /* Re-log an intent item to push the log tail forward. */

fs/xfs/xfs_attr_list.c

@@ -544,6 +544,7 @@ xfs_attr_list_ilocked(
 	struct xfs_attr_list_context	*context)
 {
 	struct xfs_inode		*dp = context->dp;
+	int				error;
 
 	xfs_assert_ilocked(dp, XFS_ILOCK_SHARED | XFS_ILOCK_EXCL);
 
@@ -554,6 +555,12 @@ xfs_attr_list_ilocked(
 		return 0;
 	if (dp->i_af.if_format == XFS_DINODE_FMT_LOCAL)
 		return xfs_attr_shortform_list(context);
+
+	/* Prerequisite for xfs_attr_is_leaf */
+	error = xfs_iread_extents(NULL, dp, XFS_ATTR_FORK);
+	if (error)
+		return error;
+
 	if (xfs_attr_is_leaf(dp))
 		return xfs_attr_leaf_list(context);
 	return xfs_attr_node_list(context);