linux-kernel - Re: [2.6 patch] unexport uts

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Date:	Wed, 21 May 2008 08:37:00 -0400
From:	Christoph Hellwig <hch@...radead.org>
To:	"Frank Ch. Eigler" <fche@...hat.com>
Cc:	Christoph Hellwig <hch@...radead.org>,
	Adrian Bunk <bunk@...nel.org>, linux-kernel@...r.kernel.org,
	"David S. Miller" <davem@...set.davemloft.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	systemtap@...rces.redhat.com, usb-storage@...ts.one-eyed-alien.net,
	linux-cifs-client@...ts.samba.org, linux-nfs@...r.kernel.org
Subject: Re: [2.6 patch] unexport uts_sem

On Tue, May 20, 2008 at 02:38:02PM -0400, Frank Ch. Eigler wrote:
> Sorry, I misspoke - this check is intended not to cross-check
> kernel-devel and the kernel itself, but the debuginfo or similar data
> that is given to describe target of a systemtap script.  I guess for
> new enough kernels we'll just do that using buildid hash codes.
> 
> By the way, there do appear to be a few suspect in-tree users of
> utsname() without uts_sem locking (usb/storage/usb.c

Just a debug printk.  Note sure why this particular one needs to
print the version, but if it really wants to do it it should rather use
UTS_RELEASE.

> cifs/connect.c,

This one is quite fishy. Not sure what it needs the name for but the
kernel utsname is probably a bad choise.  And yes, this one actually
is racy because the host name can change.

> char/random.c,

random.c is always built-in and utsname is called during the
single-threaded kernel initialization phase, so this is safe.

> fs/lockd/clntproc.c, ...).

Yes, this one is racy.  Should probably be fixed by starting lockd
with CLONE_NEWUTS so that it never changed during it's lifetime.
It's probably not a good idea when it changes with outstanding lockd
request anyway.

> If these need to be fixed,
> then wouldn't uts_sem need to come back exported?
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