From: Andrew Morton <akpm@linux-foundation.org>
To: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Pavel Emelyanov <xemul@parallels.com>,
Andrew Vagin <avagin@openvz.org>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Oleg Nesterov <oleg@redhat.com>, Greg KH <greg@kroah.com>
Subject: Re: [PATCH] pidns: remove recursion from free_pid_ns() v5
Date: Wed, 10 Oct 2012 13:54:08 -0700 [thread overview]
Message-ID: <20121010135408.515c2e21.akpm@linux-foundation.org> (raw)
In-Reply-To: <20121010204256.GD29501@moon>
On Thu, 11 Oct 2012 00:42:56 +0400
Cyrill Gorcunov <gorcunov@openvz.org> wrote:
> The free_pid_ns function done in recursion fashion:
>
> free_pid_ns(parent)
> put_pid_ns(parent)
> kref_put(&ns->kref, free_pid_ns);
> free_pid_ns
>
> thus if there was a huge nesting of namespaces the userspace
> may trigger avalanche calling of free_pid_ns leading to
> kernel stack exhausting and a panic eventually.
>
> This patch turns the recursion into iterative loop.
>
> v5 (from oleg@):
> - Drop @ret variable
> - Make put_pid_ns non-inline since it grows in size,
> in turn make free_pid_ns static
OK, let's try that. I'll sit on this until -rc2 to give it a bit of
time to cook.
A -stable backport might be needed. What capabilities does userspace
need to be able to trigger the kernel stack overflow?
next prev parent reply other threads:[~2012-10-10 20:54 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-10 20:42 [PATCH] pidns: remove recursion from free_pid_ns() v5 Cyrill Gorcunov
2012-10-10 20:54 ` Andrew Morton [this message]
2012-10-10 20:59 ` Eric W. Biederman
2012-10-10 21:14 ` Cyrill Gorcunov
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