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Date: Fri, 14 Aug 2015 19:59:44 +0200
From: Oleg Nesterov <oleg@redhat.com>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>,
        Andrew Morton <akpm@linux-foundation.org>,
        Kees Cook <keescook@chromium.org>, David Howells <dhowells@redhat.com>,
        linux-kernel@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Rik van Riel <riel@redhat.com>,
        Vladimir Davydov <vdavydov@parallels.com>,
        Ricky Zhou <rickyz@chromium.org>, Julien Tinnes <jln@google.com>
Subject: Re: [PATCH 1/2] unshare: Unsharing a thread does not require
	unsharing a vm
Message-ID: <20150814175944.GA16652@redhat.com>
References: <20150806134426.GA6843@redhat.com> <871tf9cnbi.fsf_-_@x220.int.ebiederm.org> <87vbclb8op.fsf_-_@x220.int.ebiederm.org> <20150812174847.GA6703@redhat.com> <87614k73mo.fsf@x220.int.ebiederm.org> <20150813125550.GA13984@redhat.com> <87vbcjyzac.fsf@x220.int.ebiederm.org> <20150813161718.GA23114@redhat.com> <87vbcjtapu.fsf@x220.int.ebiederm.org> <20150813165011.GA25284@redhat.com>
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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.