linux-kernel - Re: [PATCH] user_ns: use correct check for single-threadedness

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Message-ID: <20150806143541.GA9414@redhat.com>
Date:	Thu, 6 Aug 2015 16:35:41 +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] user_ns: use correct check for single-threadedness

On 08/05, Eric W. Biederman wrote:
>
> So I have to ask.

I hope you are asking someone else, not me ;) I never understood what
exactly we try to restrict and why.

> Is it possible to rework these checks such that we
> look at the sighand struct and signal sharing handling sharing instead
> of the count on the mm_struct?

Then why we can't simply check thread_group_empty() == T ? Why should we
worry about CLONE_SIGHAND at all?

Oleg.

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