linux-kernel - Re: Racy manipulation of task_struct->flags in cgroups code causes hard to reproduce kernel panics

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Message-ID: <CAGXu5j+P_kcgZuqYsemgL0KU_zRhz5HGJ6seh2oLyyst=cZP6g@mail.gmail.com>
Date:	Sat, 20 Sep 2014 10:15:50 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Zefan Li <lizefan@...wei.com>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	Ingo Molnar <mingo@...hat.com>, Tejun Heo <tj@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	cgroups@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	fernando_b1@....ntt.co.jp
Subject: Re: Racy manipulation of task_struct->flags in cgroups code causes
 hard to reproduce kernel panics

On Sat, Sep 20, 2014 at 7:30 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Sat, Sep 20, 2014 at 01:55:54PM +0800, Zefan Li wrote:
>> We should make the updating of this flag atomic.
>
>>  /* Per-process atomic flags. */
>>  #define PFA_NO_NEW_PRIVS 0x00000001  /* May not gain new privileges. */
>> +#define PFA_SPREAD_PAGE  0x00000002  /* Spread page cache over cpuset */
>> +#define PFA_SPREAD_SLAB  0x00000004  /* Spread some slab caches over cpuset */
>
> Ooh, I was not ware we had those.. /me checks where that came from. Hmm
> weird, while I did get that patch it had a seccomp prefix when landing
> in my inbox so I ignored it. However the commit has a sched prefix
> (which I would not have ignored). Dubious things happened here.

The series went through a lot of revisions, so it probably gained the
sched prefix later in its life. Is there anything that needs changing
about how this has been implemented?

-Kees

-- 
Kees Cook
Chrome OS Security
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