ovl: handle ATTR_KILL*

Before 4bacc9c9234c ("overlayfs: Make f_path...") file->f_path pointed to
the underlying file, hence suid/sgid removal on write worked fine.

After that patch file->f_path pointed to the overlay file, and the file
mode bits weren't copied to overlay_inode->i_mode.  So the suid/sgid
removal simply stopped working.

The fix is to copy the mode bits, but then ovl_setattr() needs to clear
ATTR_MODE to avoid the BUG() in notify_change().  So do this first, then in
the next patch copy the mode.

Reported-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: 4bacc9c9234c ("overlayfs: Make f_path always point to the overlay and f_inode to the underlay")
Cc: <stable@vger.kernel.org>

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index c831c2e..1233992 100644 (file)
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -80,6 +80,9 @@ int ovl_setattr(struct dentry *dentry, struct iattr *attr)
                                goto out_drop_write;
                }
 
+               if (attr->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID))
+                       attr->ia_valid &= ~ATTR_MODE;
+
                inode_lock(upperdentry->d_inode);
                err = notify_change(upperdentry, attr, NULL);
                if (!err)