netdev - Re: [PATCH v11 07/12] seccomp: add SECCOMP_RET

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Message-ID: <CAGXu5jJQhfSSwTU5fSGR_Q57LAQBFW25A_FtR2GFsxyT_ibnzQ@mail.gmail.com>
Date:	Mon, 27 Feb 2012 10:09:38 -0800
From:	Kees Cook <keescook@...omium.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Will Drewry <wad@...omium.org>, linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org, linux-doc@...r.kernel.org,
	kernel-hardening@...ts.openwall.com, netdev@...r.kernel.org,
	x86@...nel.org, arnd@...db.de, davem@...emloft.net, hpa@...or.com,
	mingo@...hat.com, peterz@...radead.org, rdunlap@...otime.net,
	mcgrathr@...omium.org, tglx@...utronix.de, luto@....edu,
	eparis@...hat.com, serge.hallyn@...onical.com, djm@...drot.org,
	scarybeasts@...il.com, indan@....nu, pmoore@...hat.com,
	akpm@...ux-foundation.org, corbet@....net, eric.dumazet@...il.com,
	markus@...omium.org, coreyb@...ux.vnet.ibm.com
Subject: Re: [PATCH v11 07/12] seccomp: add SECCOMP_RET_ERRNO

On Mon, Feb 27, 2012 at 9:11 AM, Oleg Nesterov <oleg@...hat.com> wrote:
> On 02/24, Will Drewry wrote:
>>
>>  static u32 seccomp_run_filters(int syscall)
>>  {
>>       struct seccomp_filter *f;
>> -     u32 ret = SECCOMP_RET_KILL;
>>       static const struct bpf_load_fn fns = {
>>               bpf_load,
>>               sizeof(struct seccomp_data),
>>       };
>> +     u32 ret = SECCOMP_RET_ALLOW;
>>       const void *sc_ptr = (const void *)(uintptr_t)syscall;
>>
>> +     /* Ensure unexpected behavior doesn't result in failing open. */
>> +     if (unlikely(current->seccomp.filter == NULL))
>> +             ret = SECCOMP_RET_KILL;
>
> Is "seccomp.filter == NULL" really possible?

It should not be, but I'm much more comfortable with this failing
closed. I think it's important to be as defensive as possible with
this code given its intended use.

-Kees

-- 
Kees Cook
ChromeOS Security
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