linux-kernel - umount(/proc) after CLONE

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Message-ID: <481609A5.1080905@msgid.tls.msk.ru>
Date:	Mon, 28 Apr 2008 21:30:13 +0400
From:	Michael Tokarev <mjt@....msk.ru>
To:	Linux-kernel <linux-kernel@...r.kernel.org>
Subject: umount(/proc) after CLONE_NEWNS in 2.6.25?

Since 2.6.25, it isn't possible anymore to umount
/proc after clone(CLONE_NEWNS).  It worked fine
before.  E.g:

# strace newnamespace umount -n /proc

2.6.24:

[pid 30121] clone(child_stack=0xff8c21f4, flags=CLONE_NEWNS|SIGCHLD) = 30122
[pid 30122] execve("/usr/sbin/umount", ["umount", "-n", "/proc"])
...
[pid 30122] oldumount("/proc")          = 0


2.6.25:

[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?

Thanks.

/mjt
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