Re: [kernel-hardening] [RFC PATCH] lib: Harden csum_partial_copy_from_user

[Vaishali Thakkar <vaishali.thakkar@oracle.com>]

On Thursday 03 November 2016 11:35 PM, Mark Rutland wrote:
> On Thu, Nov 03, 2016 at 10:26:41AM +0530, Vaishali Thakkar wrote:
>> On Thursday 03 November 2016 09:53 AM, Mark Rutland wrote:
>>> On Thu, Nov 03, 2016 at 07:44:35AM +0530, Vaishali Thakkar wrote:
>>>> On Thursday 03 November 2016 03:29 AM, Kees Cook wrote:
>>>>> On Wed, Nov 2, 2016 at 2:44 PM, Mark Rutland <mark.rutland@arm.com> wrote:
>>>>>> I know that both arm64 and x86 have a check_object_size() call in their
>>>>>> __copy_from_user() implementations.
>>>
>>>>>> Is that missing on some architectures?
> 
>>> Looking again, a grep shows many (even those with MMUs) don't do anything at
>>> all in v4.9-rc2:
>>>
>>> [mark@remoulade:~/src/linux]% for ARCH in arch/*; do
>>> printf "%d %s\n" $(git grep check_object_size -- "${ARCH}" | wc -l) ${ARCH};
>>> done | sort -n
> 
>> Hmm, should we go for sending patches for them? [atleast for the ones with MMUs
>> and then may be maintainers/developers can check the change]
> 
> If Al's uaccess unification work is arriving shortly, sending patches for those
> in parallel is just going to make matters more painful.
> 
> So it really depends on when that's likely to appear.

Makes sense.
 
>> Also, I think same goes for the the kasan_check. We have only arm64 and x86  
>> with these checks.
> 
> Yes. I'd hoped to collect all of those behind a common helper, something like:
> 
> static inline void check_uaccess_read(void *kaddr, const void __user *uaddr, unsigned long n)
> {
> 	kasan_check_write(kaddr, n);
> 	check_object_size(kaddr, n, false);
> 	any_uaddr_sanity_check(uaddr, n);
> }

Ok, sounds reasonable. 

Thanks.
 
> Thanks,
> Mark.
> 

-- 
Vaishali