From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [RFC PATCH (resend)] block layer zero-copy: missing
 access_ok() check
Date: Thu, 21 Mar 2013 17:33:13 -0400 (EDT)
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Cc: mathieu.desnoyers@efficios.com, linux-arch@vger.kernel.org, axboe@kernel.dk, security@kernel.org, gregkh@linuxfoundation.org, viro@zeniv.linux.org.uk, npiggin@kernel.dk

From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Fri, 15 Mar 2013 10:21:41 -0700

> Adding linux-arch. Guys, can you check your architectures?
 ...
>> * sparc: access_ok missing in get_user_pages_fast,
>>   -> no indication of any _PAGE_USER flag.

Well, access_ok() returns 1 unconditionally on sparc64.  I can add a
call there if you want.  :-)

And that's because the user virtual address space is %100 segregated
from the privileged one.  There are no "user address ranges"
vs. kernel ones.

For example, we can and do give 64-bit processes the full 64-bit
virtual address space for user mappings.

The page tables, outside of swapper_pg_dir, only map user pages.