[PATCH 8/9] Unionfs: fix unionfs_setattr to handle ATTR_KILL_S*ID

[Erez Zadok <ezk@cs.sunysb.edu>]

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>
Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>
---
 fs/unionfs/inode.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/fs/unionfs/inode.c b/fs/unionfs/inode.c
index 4e59ace..6ca52f4 100644
--- a/fs/unionfs/inode.c
+++ b/fs/unionfs/inode.c
@@ -1048,6 +1048,13 @@ static int unionfs_setattr(struct dentry *dentry, struct iattr *ia)
 	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);
-- 
1.5.2.2