linux-kernel - Re: [PATCH 1/4] Cache xattr security drop check for write v2

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Date:	Sat, 18 Jun 2011 08:58:06 +0200
From:	Marco Stornelli <marco.stornelli@...il.com>
To:	Al Viro <viro@...IV.linux.org.uk>
CC:	Steven Whitehouse <swhiteho@...hat.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, chris.mason@...cle.com,
	josef@...hat.com, agruen@...bit.com,
	"Serge E. Hallyn" <serue@...ibm.com>
Subject: Re: [PATCH 1/4] Cache xattr security drop check for write v2

Hi,

Il 31/05/2011 22:07, Al Viro ha scritto:
> On Tue, May 31, 2011 at 07:42:26PM +0100, Steven Whitehouse wrote:
>
>> Yes, it should test for xattr too,
>
> Frankly, I suspect that the sanest way to handle that is this:
> 	* new superblock flag - MS_NOSEC
> 	* S_NOSEC is never set unless we have MS_NOSEC
> 	* mount_bdev() sets it before calling fill_super callback.
> 	* ocfs2 and fuse *clear* it in their fill_super
> 	* btrfs manually sets it in its ->mount()
> ... and if gfs2 or any other non-trivial fs wants to use that, it'll need
> to set MS_NOSEC in its ->mount() and take care of clearing S_NOSEC whenever
> we decide it might've gone stale (a-la your patch).
>

several fs now uses MS_NOSEC (because this flag is set in mount_bdev()) 
but I don't see any user of the function inode_has_no_xattr() in the 
latest version. If I well understand, a fs that wants to manage this 
feature has to set MS_NOSEC and calls when needed this function, isn't 
it? So at this point, why there aren't any user of this function?

Marco
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