linux-kernel - [PATCH 4.4 50/68] ovl: handle ATTR

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Message-Id: <20160808180212.198883317@linuxfoundation.org>
Date:	Mon,  8 Aug 2016 21:11:25 +0200
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Eryu Guan <eguan@...hat.com>,
	Miklos Szeredi <mszeredi@...hat.com>,
	Eric Schultz <eric@...rtuperic.com>,
	Eric Hameleers <alien@...ckware.com>
Subject: [PATCH 4.4 50/68] ovl: handle ATTR_KILL*

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Miklos Szeredi <mszeredi@...hat.com>

commit b99c2d913810e56682a538c9f2394d76fca808f8 upstream.

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@...hat.com>
Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
Fixes: 4bacc9c9234c ("overlayfs: Make f_path always point to the overlay and f_inode to the underlay")
Cc: Eric Schultz <eric@...rtuperic.com>
Cc: Eric Hameleers <alien@...ckware.com>
[backported by Eric Hameleers as seen in https://bugzilla.kernel.org/show_bug.cgi?id=150711]
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>


---
 fs/overlayfs/inode.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -63,6 +63,9 @@ int ovl_setattr(struct dentry *dentry, s
 	if (!err) {
 		upperdentry = ovl_dentry_upper(dentry);
 
+		if (attr->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID))
+			attr->ia_valid &= ~ATTR_MODE;
+
 		mutex_lock(&upperdentry->d_inode->i_mutex);
 		err = notify_change(upperdentry, attr, NULL);
 		if (!err)