From: Jeff Layton <jlayton@redhat.com>

Don't allow unionfs_setattr to trip the BUG() in notify_change. Clear
ATTR_MODE if the either ATTR_KILL_S*ID is set. This also allows the
lower filesystem to interpret these bits in its own way.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Cc: Josef 'Jeff' Sipek <jsipek@cs.sunysb.edu>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/unionfs/inode.c |    7 +++++++
 1 file changed, 7 insertions(+)

diff -puN fs/unionfs/inode.c~unionfs-fix-unionfs_setattr-to-handle-attr_kill_sid fs/unionfs/inode.c
--- a/fs/unionfs/inode.c~unionfs-fix-unionfs_setattr-to-handle-attr_kill_sid
+++ a/fs/unionfs/inode.c
@@ -1021,6 +1021,13 @@ static int unionfs_setattr(struct dentry
 	bend = dbend(dentry);
 	inode = dentry->d_inode;
 
+	/*
+	 * mode change is for clearing setuid/setgid. Allow lower filesystem
+	 * to reinterpret it in its own way.
+	 */
+	if (ia->ia_valid & (ATTR_KILL_SUID | ATTR_KILL_SGID))
+		ia->ia_valid &= ~ATTR_MODE;
+
 	for (bindex = bstart; (bindex <= bend) || (bindex == bstart);
 	     bindex++) {
 		lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
_