linux-kernel - Re: [PATCH] Reserve N process to root

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Date:	Wed, 10 Oct 2007 14:02:54 -0700 (PDT)
From:	g@...f.cl
To:	Valdis.Kletnieks@...edu
Cc:	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Reserve N process to root

> On Wed, 10 Oct 2007 09:46:22 EDT, Gustavo Chain said:
>> El Wed, 10 Oct 2007 15:14:06 +0930
>> David Newall <david@...idnewall.com> escribió:
>> > That was what I thought you had in mind; it protects from some kind
>> > of fork bomb, right?  But it doesn't seem useful unless you guarantee
>> > having a process already running (with CAP_SYS_ADMIN) *before* the
>> > bomb goes off.
>>
>> Not really, because fork bomb will never reach maximum pid possible.
>> And root will always have a "slot" to kill desired processes.
>
> What David meant was that "root will always have a slot" doesn't
> *actually*
> help unless you *also* have a way to actually *spawn* such a process.  In
> order
> to do the ps, kill, and so on that you need to recover, you need to
> already
> have either a root shell available, or a way to *get* a root shell that
> doesn't
> rely on a non-root process (so /bin/su doesn't help here).
>
> Many distros will leave a /sbin/mingetty running on tty1 through tty6, and
> you *can* use those to get a root shell.  David's point is that without
> something like that already in place, the patch doesn't help....
>
>

but once you are logged in, how can you "spawn" processes (ps, kill, and
so on) if the limit is reached ?

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