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

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Message-ID: <4816A5EB.5090402@msgid.tls.msk.ru>
Date:	Tue, 29 Apr 2008 08:36:59 +0400
From:	Michael Tokarev <mjt@....msk.ru>
To:	Al Viro <viro@...IV.linux.org.uk>
CC:	Linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: umount(/proc) after CLONE_NEWNS in 2.6.25?

Al Viro wrote:
> On Tue, Apr 29, 2008 at 03:06:38AM +0100, Al Viro wrote:
> 
>>> 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...
> 
> ... or something much simpler:
> 
> ; cat /proc/mounts |grep proc
> proc /proc proc rw,nosuid,nodev,noexec 0 0
> usbfs /proc/bus/usb usbfs rw 0 0
> ;
> 
> and unmounting the stuff mounted under /proc before doing umount /proc
> works as expected.  Amazing how well the first cup of coffee helps...

Hey.  Don't paint ME *that* dumb... ;)

It was indeed the case here.  I never tried those things on my
home machine before, and decided to experiment, but I forgot
that it has /proc/bus/usb mounted.  And for comparison I used
another machine which does NOT have that filesystem mounted.
How.. dum^Wodd... ;)

Please excuse me for the noise.

/mj
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