xfs: Check for extent overflow when adding/removing xattrs

Adding/removing an xattr can cause XFS_DA_NODE_MAXDEPTH extents to be
added. One extra extent for dabtree in case a local attr is large enough
to cause a double split.  It can also cause extent count to increase
proportional to the size of a remote xattr's value.

Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Chandan Babu R <chandanrlinux@gmail.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/libxfs/xfs_attr.c

@@ -396,6 +396,7 @@ xfs_attr_set(
 	struct xfs_trans_res	tres;
 	bool			rsvd = (args->attr_filter & XFS_ATTR_ROOT);
 	int			error, local;
+	int			rmt_blks = 0;
 	unsigned int		total;
 
 	if (XFS_FORCED_SHUTDOWN(dp->i_mount))
@@ -442,11 +443,15 @@ xfs_attr_set(
 		tres.tr_logcount = XFS_ATTRSET_LOG_COUNT;
 		tres.tr_logflags = XFS_TRANS_PERM_LOG_RES;
 		total = args->total;
+
+		if (!local)
+			rmt_blks = xfs_attr3_rmt_blocks(mp, args->valuelen);
 	} else {
 		XFS_STATS_INC(mp, xs_attr_remove);
 
 		tres = M_RES(mp)->tr_attrrm;
 		total = XFS_ATTRRM_SPACE_RES(mp);
+		rmt_blks = xfs_attr3_rmt_blocks(mp, XFS_XATTR_SIZE_MAX);
 	}
 
 	/*
@@ -460,6 +465,14 @@ xfs_attr_set(
 
 	xfs_ilock(dp, XFS_ILOCK_EXCL);
 	xfs_trans_ijoin(args->trans, dp, 0);
+
+	if (args->value || xfs_inode_hasattr(dp)) {
+		error = xfs_iext_count_may_overflow(dp, XFS_ATTR_FORK,
+				XFS_IEXT_ATTR_MANIP_CNT(rmt_blks));
+		if (error)
+			goto out_trans_cancel;
+	}
+
 	if (args->value) {
 		unsigned int	quota_flags = XFS_QMOPT_RES_REGBLKS;
 

fs/xfs/libxfs/xfs_inode_fork.h

@@ -60,6 +60,16 @@ struct xfs_ifork {
 #define XFS_IEXT_DIR_MANIP_CNT(mp) \
 	((XFS_DA_NODE_MAXDEPTH + 1 + 1) * (mp)->m_dir_geo->fsbcount)
 
+/*
+ * Adding/removing an xattr can cause XFS_DA_NODE_MAXDEPTH extents to
+ * be added. One extra extent for dabtree in case a local attr is
+ * large enough to cause a double split.  It can also cause extent
+ * count to increase proportional to the size of a remote xattr's
+ * value.
+ */
+#define XFS_IEXT_ATTR_MANIP_CNT(rmt_blks) \
+	(XFS_DA_NODE_MAXDEPTH + max(1, rmt_blks))
+
 /*
  * Fork handling.
  */