linux-kernel - Re: [PATCH 3.5 2/2] seccomp: Future-proof against silly tracers

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Message-ID: <CABqD9hanETRn77YoXb0LzgcxVJKnV6Pkfkow_b2=456rad=fNg@mail.gmail.com>
Date:	Thu, 2 Aug 2012 09:32:15 -0500
From:	Will Drewry <wad@...omium.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH 3.5 2/2] seccomp: Future-proof against silly tracers

On Thu, Jul 26, 2012 at 10:41 AM, Andy Lutomirski <luto@...capital.net> wrote:
> On Tue, Jul 17, 2012 at 4:19 PM, Andy Lutomirski <luto@...capital.net> wrote:
>> Currently, if a tracer changes a syscall nr to __NR_future_enosys,
>> behavior will differ between kernels that know about
>> __NR_future_enosys (and return -ENOSYS) and older kernels (which
>> return the value from pt_regs).  This is silly; we should just
>> return -ENOSYS.
>>
>> This is unlikely to ever happen on x86 because the return value in
>> pt_regs starts out as -ENOSYS, but a silly tracer can change that.
>>
>> Signed-off-by: Andy Lutomirski <luto@...capital.net>
>> Cc: Will Drewry <wad@...omium.org>
>> ---
>>  arch/x86/include/asm/syscall.h |   11 +++++++++++
>>  kernel/seccomp.c               |   15 +++++++++++++++
>>  2 files changed, 26 insertions(+), 0 deletions(-)
>
> Will, can you pick this, or some version of it, up in your
> seccomp-for-ARM tree or wherever your development is?

I'm still not sure about this change though the end result is nice.
Regardless, I'll explore it when I can -- my family has just increased
in size, so I'm going to be a bit delayed!

cheers!
will
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