linux-kernel - [RFC][PATCH 0/2] Correct behavior for listxattr and 'trusted' xattrs

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Date:	Tue, 2 Mar 2010 19:01:05 +1100 (EST)
From:	James Morris <jmorris@...ei.org>
To:	linux-fsdevel@...r.kernel.org
cc:	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	David Woodhouse <dwmw2@...radead.org>,
	Joel Becker <joel.becker@...cle.com>,
	Mark Fasheh <mfasheh@...e.com>, Alex Elder <aelder@....com>,
	Chris Mason <chris.mason@...cle.com>,
	a.gruenbacher@...puter.org
Subject: [RFC][PATCH 0/2] Correct behavior for listxattr and 'trusted'
 xattrs

I noticed that there are differences in the behavior of listxattr(2) for 
xattrs in the trusted namespace.

Some filesystems, such as ext[234], require CAP_SYS_ADMIN for this, i.e. 
trusted xattr names are hidden from unprivileged users.

I audited the kernel for users of the trusted xattr namespace, and found 
the following filesystems not checking for CAP_SYS_ADMIN:

  - jffs2
  - ocfs2
  - btrfs
  - xfs

I've created patches for jffs2 (tested) and ocfs2 (not tested) to add the 
check -- see following emails. btrfs and xfs have custom listxattr 
operations and will need a bit more work to fix.

I'm not sure what the initial intention was for the behavior, although 
given that several major filesystems are have been fielded with the 
CAP_SYS_ADMIN check, it seems most prudent to make this the standard 
behavior for all filesystems, in case any users are depending on it.

Thoughts?

- James
-- 
James Morris
<jmorris@...ei.org>
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