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Date:	Tue, 10 Nov 2015 17:22:30 -0800
From:	Badhri Jagan Sridharan <badhri@...gle.com>
To:	Richard Weinberger <richard.weinberger@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	David Howells <dhowells@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: init: How did init/do_mounts_rd.c overcome memory protection ?

Thanks Richard !!
That's the one that I was looking for.

On Tue, Nov 10, 2015 at 1:37 PM, Richard Weinberger
<richard.weinberger@...il.com> wrote:
> On Tue, Nov 10, 2015 at 7:38 PM, Badhri Jagan Sridharan
> <badhri@...gle.com> wrote:
>> Mighty upstream,
>>
>> I see that do_mounts_rd.c seems to make calls to sys_read and
>> sys_lseek functions. As these are syscall functions, they expects
>> some of the arguments to be from userspace.
>>
>> I was going through the article that Greg KH wrote a while back:
>> http://www.linuxjournal.com/article/8110?page=0,1 . I don't see any
>> references to set_fs/get_fs under init/*. Does the memory protection
>> get enabled only in the later stage ? Or does do_mounts_rd.c accomplish
>> this in some other way ?
>
> The stuff in init/ is PID 1 and it inherits addr_limit from the
> initial thread (PID 0 or swapper called).
> INIT_THREAD_INFO() sets addr_limit to KERNEL_DS.
>
> --
> Thanks,
> //richard
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