linux-kernel - Re: [PATCH 0/7] test_user

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Message-ID: <55C38B30.5030405@imgtec.com>
Date:	Thu, 6 Aug 2015 17:28:32 +0100
From:	James Hogan <james.hogan@...tec.com>
To:	Kees Cook <keescook@...omium.org>
CC:	LKML <linux-kernel@...r.kernel.org>,
	linux-arch <linux-arch@...r.kernel.org>,
	Linux MIPS Mailing List <linux-mips@...ux-mips.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 0/7] test_user_copy improvements

Hi Kees,

On 05/08/15 21:26, Kees Cook wrote:
> On Wed, Aug 5, 2015 at 8:48 AM, James Hogan <james.hogan@...tec.com> wrote:
>> These patches extend the test_user_copy test module to handle lots more
>> cases of user accessors which architectures can override separately, and
>> in particular those which are important for checking the MIPS Enhanced
>> Virtual Addressing (EVA) implementations, which need to handle
>> overlapping user and kernel address spaces, with special instructions
>> for accessing user address space from kernel mode.
>>
>> - Checking that kernel pointers are accepted when user address limit is
>>   set to KERNEL_DS, as done by the kernel when it internally invokes
>>   system calls with kernel pointers.
>> - Checking of the unchecked accessors (which don't call access_ok()).
>>   Some of the tests are special cased for EVA at the moment which has
>>   stricter hardware guarantees for bad user accesses than other
>>   configurations.
>> - Checking of other sets of user accessors, including the inatomic user
>>   copies, copy_in_user, clear_user, the user string accessors, and the
>>   user checksum functions, all of which need special handling in arch
>>   code with EVA.
>>
>> Tested on MIPS with and without EVA, and on x86_64.
>>
>> James Hogan (7):
>>   test_user_copy: Check legit kernel accesses
>>   test_user_copy: Check unchecked accessors
>>   test_user_copy: Check __clear_user()/clear_user()
>>   test_user_copy: Check __copy_in_user()/copy_in_user()
>>   test_user_copy: Check __copy_{to,from}_user_inatomic()
>>   test_user_copy: Check user string accessors
>>   test_user_copy: Check user checksum functions
>>
>>  lib/test_user_copy.c | 221 +++++++++++++++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 221 insertions(+)
>>
>> Cc: Kees Cook <keescook@...omium.org>
>> Cc: Andrew Morton <akpm@...ux-foundation.org>
> 
> Ooooh! Nice! This is great, thank you. :) Great to hear it helped find
> a bug too. :)
> 
> I'm wondering if we need to macro-ize any of these. Probably not, but
> it just feels like there's a lot of repeated stuff now. But I think
> it's a bit of an illusion since each test is ever so slightly
> different from the others.

Yeh, I wondered that too, but I agree they're all slightly different in
their requirements so it'd just end up confusing things.

> 
> Acked-by: Kees Cook <keescook@...omium.org>

Thanks!

James


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