linux-kernel - Re: [PATCH 2/2] exec: Make do_coredump more robust and safer when using pipes in core

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Date:	Mon, 29 Jun 2009 01:32:00 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Neil Horman <nhorman@...driver.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, earl_chew@...lent.com,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH 2/2] exec: Make do_coredump more robust and safer when
	using pipes in core_pattern (v3)

On 06/28, Neil Horman wrote:
>
> On Mon, Jun 29, 2009 at 12:24:55AM +0200, Oleg Nesterov wrote:
> >
> > Perhaps this sysctl should be added in a separate patch? This patch mixes
> > differents things imho.
> >
> No, I disagree. If we're going to have a sysctl, It should be added in this
> patch.  I agree that since these processes run as root, we can have all sort of
> bad things happen.  But I think theres an advantage to being able to limit the
> damage that a core_pattern process can do if it never exits.

Yes, but why it should be added in this patch?

> > But in fact I don't really understand why do we need the new sysctl. Yes,
> > if the collecting process never exits, the coredumping thread can't be reaped.
> > But this process runs as root, it can do other bad things. And let's suppose
> > it just does nothing, say sleeps forever, and do not read the data from pipe.
> > In that case, regardless of any sysctls, ->core_dump() never finishes too.
> >
> Not always true, in the event that the core file is smaller than the pipe size.

sure,

> But regardless, if ->core_dump never returns due to the aforementioned
> situation, the sysctl provides the ability to mitigate the damange that can do,
> since the dump count is held while ->core_dump is called.

Yes, I misread the sysctl code. Perhaps another reason to split this patch ;)

Oleg.

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