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Date:   Mon, 8 Jun 2020 16:48:34 +0530
From:   afzal mohammed <afzal.mohd.ma@gmail.com>
To:     Arnd Bergmann <arnd@arndb.de>
Cc:     Russell King <linux@armlinux.org.uk>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: ARM: vmsplit 4g/4g
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Hi,

On Sun, Jun 07, 2020 at 09:26:26PM +0200, Arnd Bergmann wrote:

> I think you have to use get_user_pages() though instead of
> get_user_pages_fast(),
> in order to be able to check the permission bits to prevent doing a
> copy_to_user()
> into read-only mappings.

i was not aware of this, is it documented somewhere ?, afaiu,
difference b/n get_user_pages_fast() & get_user_pages() is that fast
version will try to pin pages w/o acquiring mmap_sem if possible.

> Do you want me to review the uaccess patch to look for any missing
> corner cases, or do you want to do the whole set of user access helpers
> first?

i will cleanup and probably post RFC initially for the changes
handling copy_{from,to}_user() to get feedback.

Regards
afzal