From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [kernel-hardening] Re: [PATCH v9 1/4] syscalls: Verify address
 limit before returning to user-mode
Date: Wed, 10 May 2017 01:14:31 -0700
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To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Mark Rutland <mark.rutland@arm.com>, Kernel Hardening <kernel-hardening@lists.openwall.com>, Greg KH <greg@kroah.com>, Heiko Carstens <heiko.carstens@de.ibm.com>, LKML <linux-kernel@vger.kernel.org>, David Howells <dhowells@redhat.com>, Dave Hansen <dave.hansen@intel.com>, "H . Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@kernel.org>, Pavel Tikhomirov <ptikhomirov@virtuozzo.com>, Peter Zijlstra <a.p.zijlstra@chello.nl>, linux-s390 <linux-s390@vger.kernel.org>, the arch/x86 maintainers <x86@kernel.org>, Russell King <linux@armlinux.org.uk>, Will Deacon <will.deacon@arm.com>, Christoph Hellwig <hch@infradead.org>, Christian Borntraeger <borntraeger@de.ibm.com>, =?iso-8859-1?Q?Ren=E9?= Nyffenegger <mail@renenyffenegger.ch>, Catalin Marinas <catalin.marinas@arm.com>, "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>, Rik van Riel <riel@redhat.com>, Kees Cook <keescook@c>
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On Wed, May 10, 2017 at 09:08:41AM +0100, Al Viro wrote:
> On Wed, May 10, 2017 at 09:37:04AM +0200, Arnd Bergmann wrote:
> 
> > > How about trying to remove all of them?  If we could actually get rid
> > > of all of them, we could drop the arch support, and we'd get faster,
> > > simpler, shorter uaccess code throughout the kernel.
> 
> BTW, not all get_user() under KERNEL_DS are plain loads.  There is an
> exception - probe_kernel_read().

And various calls that looks like opencoded versions, e.g. drivers/dio
or the ELF loader.

But in the long run we'll just need a separate primitive for that,
but that can wait until the set_fs calls outside the core code are
gone.