linux-kernel - Re: [PATCH v7 4/9] seccomp: move no_new

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Message-ID: <CALCETrU9x05ADgz9JToiw_BuCPz1h0xmOh=1R3eojL9far1aEA@mail.gmail.com>
Date:	Tue, 24 Jun 2014 12:34:36 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Kees Cook <keescook@...omium.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Alexei Starovoitov <ast@...mgrid.com>,
	"Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Daniel Borkmann <dborkman@...hat.com>,
	Will Drewry <wad@...omium.org>,
	Julien Tinnes <jln@...omium.org>,
	David Drysdale <drysdale@...gle.com>,
	Linux API <linux-api@...r.kernel.org>, X86 ML <x86@...nel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>, linux-mips@...ux-mips.org,
	linux-arch <linux-arch@...r.kernel.org>,
	LSM List <linux-security-module@...r.kernel.org>
Subject: Re: [PATCH v7 4/9] seccomp: move no_new_privs into seccomp

On Tue, Jun 24, 2014 at 12:30 PM, Oleg Nesterov <oleg@...hat.com> wrote:
> On 06/24, Andy Lutomirski wrote:
>>
>> On Tue, Jun 24, 2014 at 12:18 PM, Oleg Nesterov <oleg@...hat.com> wrote:
>> >>
>> >> -struct seccomp { };
>> >> +struct seccomp {
>> >> +     unsigned long flags;
>> >> +};
>> >
>> > A bit messy ;)
>> >
>> > I am wondering if we can simply do
>> >
>> >         static inline bool current_no_new_privs(void)
>> >         {
>> >                 if (current->no_new_privs)
>> >                         return true;
>> >
>> >         #ifdef CONFIG_SECCOMP
>> >                 if (test_thread_flag(TIF_SECCOMP))
>> >                         return true;
>> >         #endif
>>
>> Nope -- privileged users can enable seccomp w/o nnp.
>
> Indeed, I am stupid.
>
> Still it would be nice to cleanup this somehow. The new member is only
> used as a previous ->no_new_privs, just it is long to allow the concurent
> set/get. Logically it doesn't even belong to seccomp{}.

We could add an unsigned long atomic flags field to task_struct.

Grr.  Why isn't there an unsigned *int* atomic bitmask type?  Even u64
would be better.  unsigned long is useless.

>
> Oleg.
>



-- 
Andy Lutomirski
AMA Capital Management, LLC
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