linux-kernel - Re: [PATCH 1/2] unshare: Unsharing a thread does not require unsharing a vm

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Message-ID: <20150814175944.GA16652@redhat.com>
Date:	Fri, 14 Aug 2015 19:59:44 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	"Kirill A. Shutemov" <kirill@...temov.name>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kees Cook <keescook@...omium.org>,
	David Howells <dhowells@...hat.com>,
	linux-kernel@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Rik van Riel <riel@...hat.com>,
	Vladimir Davydov <vdavydov@...allels.com>,
	Ricky Zhou <rickyz@...omium.org>,
	Julien Tinnes <jln@...gle.com>
Subject: Re: [PATCH 1/2] unshare: Unsharing a thread does not require
	unsharing a vm

On 08/13, Oleg Nesterov wrote:
>
> On 08/13, Eric W. Biederman wrote:
> >
> > In the sense of document when these tests apply I think it makes a
> > teensy bit of sense to have the CLONE_VM there.  But if you want to send
> > me a cosmetic patch that removes that I will add it to my tree, with the
> > other two patches.
>
> Will do ;)

Yes, I still think it is pointless to check sighand->count if CLONE_VM.

> Eric, I need to run away, I'll try to answer other parts of our confusing
> discussion tomorrow.

No, lest stop it.

Yes, I was wrong, we can't avoid sighand->count check. Somehow I absolutely
forgot that we also need to ensure that unshare(SIGHAND) can't wrongly _fail_.

Oleg.

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