xfs: error out if trying to add attrs and anextents > 0

commit 0f352f8e upstream.

We shouldn't assert if somehow we end up trying to add an attr fork to
an inode that apparently already has attr extents because this is an
indication of on-disk corruption.  Instead, return an error code to
userspace.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/xfs/libxfs/xfs_bmap.c

@@ -1153,6 +1153,10 @@ xfs_bmap_add_attrfork(
 		goto trans_cancel;
 	if (XFS_IFORK_Q(ip))
 		goto trans_cancel;
+	if (ip->i_d.di_anextents != 0) {
+		error = -EFSCORRUPTED;
+		goto trans_cancel;
+	}
 	if (ip->i_d.di_aformat != XFS_DINODE_FMT_EXTENTS) {
 		/*
 		 * For inodes coming from pre-6.2 filesystems.
@@ -1160,7 +1164,6 @@ xfs_bmap_add_attrfork(
 		ASSERT(ip->i_d.di_aformat == 0);
 		ip->i_d.di_aformat = XFS_DINODE_FMT_EXTENTS;
 	}
-	ASSERT(ip->i_d.di_anextents == 0);
 
 	xfs_trans_ijoin(tp, ip, 0);
 	xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);