linux-kernel - Re: [PATCH v5 2/3] asm-generic: Add generic seccomp.h for secure computing mode 1

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Date:	Wed, 23 Jul 2014 21:41:30 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	AKASHI Takahiro <takahiro.akashi@...aro.org>,
	Will Drewry <wad@...omium.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>, dsaxena@...aro.org,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	linaro-kernel@...ts.linaro.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 2/3] asm-generic: Add generic seccomp.h for secure
 computing mode 1

On Wed, Jul 23, 2014 at 8:40 PM, Andy Lutomirski <luto@...capital.net> wrote:
> On 07/22/2014 02:14 AM, AKASHI Takahiro wrote:
>>
>> Those values (__NR_seccomp_*) are used solely in secure_computing()
>> to identify mode 1 system calls. If compat system calls have different
>> syscall numbers, asm/seccomp.h may override them.
>>
>> Acked-by: Arnd Bergmann <arnd@...db.de>
>> Signed-off-by: AKASHI Takahiro <takahiro.akashi@...aro.org>
>> ---
>>   include/asm-generic/seccomp.h |   28 ++++++++++++++++++++++++++++
>>   1 file changed, 28 insertions(+)
>>   create mode 100644 include/asm-generic/seccomp.h
>>
>> diff --git a/include/asm-generic/seccomp.h b/include/asm-generic/seccomp.h
>> new file mode 100644
>> index 0000000..5e97022
>> --- /dev/null
>> +++ b/include/asm-generic/seccomp.h
>> @@ -0,0 +1,28 @@
>> +/*
>> + * include/asm-generic/seccomp.h
>> + *
>> + * Copyright (C) 2014 Linaro Limited
>> + * Author: AKASHI Takahiro <takahiro.akashi@...aro.org>
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License version 2 as
>> + * published by the Free Software Foundation.
>> + */
>> +#ifndef _ASM_GENERIC_SECCOMP_H
>> +#define _ASM_GENERIC_SECCOMP_H
>> +
>> +#include <asm-generic/unistd.h>
>> +
>> +#if defined(CONFIG_COMPAT) && !defined(__NR_seccomp_read_32)
>> +#define __NR_seccomp_read_32           __NR_read
>> +#define __NR_seccomp_write_32          __NR_write
>> +#define __NR_seccomp_exit_32           __NR_exit
>> +#define __NR_seccomp_sigreturn_32      __NR_rt_sigreturn
>> +#endif /* CONFIG_COMPAT && ! already defined */
>> +
>> +#define __NR_seccomp_read              __NR_read
>> +#define __NR_seccomp_write             __NR_write
>> +#define __NR_seccomp_exit              __NR_exit
>> +#define __NR_seccomp_sigreturn         __NR_rt_sigreturn
>
>
> I don't like these names.  __NR_seccomp_read sounds like the number of a
> syscall called seccomp_read.
>
> Also, shouldn't something be including this header?  I'm confused.

Ah! Good catch. These names are correct (see kernel/seccomp.c's
mode1_syscalls and mode1_syscalls_32 arrays), but the location of this
change was unexpected. I was expecting this file to live in
arch/*/include/asm/seccomp.h, not in include/asm-generic/seccomp.h.

However, since it's always the same list, it might make sense to
consolidate them into a single place as a default to make arch porting
easier. However, I think that should be a separate patch.

-Kees

-- 
Kees Cook
Chrome OS Security
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