linux-kernel - Re: [PATCH 6/7] mm: kill vma flag VM

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Message-ID: <20120402144821.GA3334@redhat.com>
Date:	Mon, 2 Apr 2012 16:48:21 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
Cc:	Cyrill Gorcunov <gorcunov@...nvz.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Eric Paris <eparis@...hat.com>,
	"linux-security-module@...r.kernel.org"@jasper.es
Subject: Re: [PATCH 6/7] mm: kill vma flag VM_EXECUTABLE

On 04/02, Konstantin Khlebnikov wrote:
>
> In this patch I leave mm->exe_file lockless.
> After exec/fork we can change it only for current task and only if mm->mm_users == 1.
>
> something like this:
>
> task_lock(current);

OK, this protects against the race with get_task_mm()

> if (atomic_read(&current->mm->mm_users) == 1)

this means PR_SET_MM_EXE_FILE can fail simply because someone did
get_task_mm(). Or the caller is multithreaded.

> 	set_mm_exe_file(current->mm, new_file);

No, fput() can sleep.

Oleg.

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