linux-kernel - Re: umount(/proc) after CLONE

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Message-ID: <20080429020638.GJ5882@ZenIV.linux.org.uk>
Date:	Tue, 29 Apr 2008 03:06:38 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Michael Tokarev <mjt@....msk.ru>
Cc:	Linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: umount(/proc) after CLONE_NEWNS in 2.6.25?

On Tue, Apr 29, 2008 at 02:47:18AM +0100, Al Viro wrote:
> On Mon, Apr 28, 2008 at 07:27:59PM +0100, Al Viro wrote:
> > > [pid 6308] clone(child_stack=0xbfc9de94, flags=CLONE_NEWNS|SIGCHLD) = 6309
> > > [pid  6309] execve("/usr/sbin/umount", ["umount", "-n", "/proc"])
> > > ...
> > > [pid  6309] oldumount("/proc")          = -1 EBUSY (Device or resource busy)
> > > umount: /proc: device is busy
> > >
> > > Yes, various NAMESPACEs are enabled (i'm trying to experiment with
> > > those).
> > >
> > > Is it intentional?
> > 
> > It's very odd.  Could you bisect that down to offending changeset or
> > at least narrow the things down to -rc<something>?  I'm going down right
> > now, so won't be able to look into that until tonight...
> 
> Check the version of umount(8) you've got.  And see if that strace happens
> to have open of /proc/mounts, without matching close by the time it calls
> umount().  util-linux-ng 2.13.1 is _that_ dumb...

Umm...  Looks like something more odd is going on...
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