Re: [PATCH for 4.18 2/6] rseq: use get_user/put_user rather than __get_user/__put_user

[Mathieu Desnoyers]

----- On Jul 9, 2018, at 2:04 PM, Linus Torvalds torvalds@xxxxxxxxxxxxxxxxxxxx wrote:

> On Mon, Jul 9, 2018 at 10:28 AM Mathieu Desnoyers
> <mathieu.desnoyers@xxxxxxxxxxxx> wrote:
>>
>> So, another twist to this story: ppc32 does not implement u64 get_user().
> 
> I was going to say that "that's not possible", since we actually have
> 64-bit arguments at least in the form of "loff_t __user *".
> 
> But when I started looking, it turns out that yeah, we do
> "copy_from_user()" on them, and instead made the x86 copy_from_user()
> have special cases for constant sizes.
> 
> So a 8-byte copy_from_user() is fine. It ends up being a "get_user()"
> on x86 anyway.

Given that this memory area has already been checked with access_ok()
on rseq registration, are you fine with leaving
__get_user/__put_user/__copy_{from,to}_user in place so we do the
minimal change at this stage of rc, or should I go ahead and replace
the lot with get_user/put_user/copy_{from,to}_user ?

Thanks,

Mathieu


-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com