From: Arun Sharma <asharma@fb.com>
To: Balbir Singh <bsingharora@gmail.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
akpm@linux-foundation.org,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Subject: Re: [PATCH] mm: Enable MAP_UNINITIALIZED for archs with mmu
Date: Fri, 24 Feb 2012 11:11:12 -0800 [thread overview]
Message-ID: <4F47E0D0.9030409@fb.com> (raw)
In-Reply-To: <CAKTCnzk7TgDeYRZK0rCugopq0tO7BtM8jM9U0RJUTqNtz42ZKw@mail.gmail.com>
On 2/24/12 6:51 AM, Balbir Singh wrote:
> On Fri, Feb 24, 2012 at 8:17 AM, KAMEZAWA Hiroyuki
> <kamezawa.hiroyu@jp.fujitsu.com> wrote:
>>> They don't have access to each other's VMAs, but if "accidentally" one
>>> of them comes across an uninitialized page with data from another task,
>>> it's not a violation of the security model.
>
> Can you expand more on the single address space model?
I haven't thought this through yet. But I know that just adding
&& (cgroup_task_count() == 1)
to page_needs_clearing() is not going to do it. We'll have to design a
new mechanism (cgroup_mm_count_all()?) and make sure that it doesn't
race with fork() and inadvertently expose pages from the new address
space to the existing one.
A uid based approach such as the one implemented by Davide Libenzi
http://thread.gmane.org/gmane.linux.kernel/548928
http://thread.gmane.org/gmane.linux.kernel/548926
would probably apply the optimization to more use cases - but
conceptually a bit more complex. If we go with this more relaxed
approach, we'll have to design a race-free cgroup_uid_count() based
mechanism.
-Arun
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WARNING: multiple messages have this Message-ID (diff)
From: Arun Sharma <asharma@fb.com>
To: Balbir Singh <bsingharora@gmail.com>
Cc: <linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>,
<akpm@linux-foundation.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Subject: Re: [PATCH] mm: Enable MAP_UNINITIALIZED for archs with mmu
Date: Fri, 24 Feb 2012 11:11:12 -0800 [thread overview]
Message-ID: <4F47E0D0.9030409@fb.com> (raw)
In-Reply-To: <CAKTCnzk7TgDeYRZK0rCugopq0tO7BtM8jM9U0RJUTqNtz42ZKw@mail.gmail.com>
On 2/24/12 6:51 AM, Balbir Singh wrote:
> On Fri, Feb 24, 2012 at 8:17 AM, KAMEZAWA Hiroyuki
> <kamezawa.hiroyu@jp.fujitsu.com> wrote:
>>> They don't have access to each other's VMAs, but if "accidentally" one
>>> of them comes across an uninitialized page with data from another task,
>>> it's not a violation of the security model.
>
> Can you expand more on the single address space model?
I haven't thought this through yet. But I know that just adding
&& (cgroup_task_count() == 1)
to page_needs_clearing() is not going to do it. We'll have to design a
new mechanism (cgroup_mm_count_all()?) and make sure that it doesn't
race with fork() and inadvertently expose pages from the new address
space to the existing one.
A uid based approach such as the one implemented by Davide Libenzi
http://thread.gmane.org/gmane.linux.kernel/548928
http://thread.gmane.org/gmane.linux.kernel/548926
would probably apply the optimization to more use cases - but
conceptually a bit more complex. If we go with this more relaxed
approach, we'll have to design a race-free cgroup_uid_count() based
mechanism.
-Arun
next prev parent reply other threads:[~2012-02-24 19:11 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-18 18:51 [PATCH] mm: Enable MAP_UNINITIALIZED for archs with mmu Arun Sharma
2012-01-18 18:51 ` Arun Sharma
2012-01-19 2:42 ` KAMEZAWA Hiroyuki
2012-01-19 2:42 ` KAMEZAWA Hiroyuki
2012-01-24 0:54 ` Arun Sharma
2012-01-24 0:54 ` Arun Sharma
2012-01-24 3:07 ` KAMEZAWA Hiroyuki
2012-01-24 3:07 ` KAMEZAWA Hiroyuki
2012-01-25 1:45 ` Arun Sharma
2012-01-25 1:45 ` Arun Sharma
2012-02-22 0:34 ` Arun Sharma
2012-02-22 0:34 ` Arun Sharma
2012-02-23 7:45 ` Balbir Singh
2012-02-23 7:45 ` Balbir Singh
2012-02-23 18:42 ` Arun Sharma
2012-02-23 18:42 ` Arun Sharma
2012-02-24 2:47 ` KAMEZAWA Hiroyuki
2012-02-24 2:47 ` KAMEZAWA Hiroyuki
2012-02-24 14:51 ` Balbir Singh
2012-02-24 14:51 ` Balbir Singh
2012-02-24 19:11 ` Arun Sharma [this message]
2012-02-24 19:11 ` Arun Sharma
2012-02-25 4:13 ` Balbir Singh
2012-02-25 4:13 ` Balbir Singh
2012-02-27 18:32 ` Arun Sharma
2012-02-27 18:32 ` Arun Sharma
2012-02-24 19:26 ` Arun Sharma
2012-02-24 19:26 ` Arun Sharma
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