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Message-ID: <20170510192035.GI32165@htj.duckdns.org>
Date: Wed, 10 May 2017 15:20:35 -0400
From: Tejun Heo <tj@...nel.org>
To: Daniel Micay <danielmicay@...il.com>
Cc: Christoph Lameter <cl@...ux.com>, Kees Cook <keescook@...omium.org>,
kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH] mark most percpu globals as __ro_after_init
On Wed, May 10, 2017 at 01:59:32PM -0400, Daniel Micay wrote:
> On Wed, 2017-05-10 at 13:52 -0400, Tejun Heo wrote:
> > Hello, Daniel.
> >
> > On Wed, May 10, 2017 at 01:36:37PM -0400, Daniel Micay wrote:
> > > Moving pcpu_base_addr to this section comes from PaX where it's part
> > > of
> > > KERNEXEC. This extends it to the rest of the globals only written by
> > > the
> > > init code.
> >
> > How did you test the patch?
>
> Booted / did some stuff on x86 (it's running right now), and currently
> building it for a 3.18 arm64 kernel to test there.
>
> >
> > > -static struct list_head *pcpu_slot __read_mostly; /* chunk list
> > > slots */
> > > +static struct list_head *pcpu_slot __ro_after_init; /* chunk list
> > > slots */
> >
> > At least this one isn't read only.
>
> It's the array it points to being modified after it gets assigned to
> during init with pcpu_slot = memblock_virt_alloc(...), not the pointer
> variable itself. The references after init are all pcpu_slot[...]
> including taking references to slots in the array so there's always a
> dereference happening first.
Ah, right. Cool, applying to percpu/for-4.13.
Thanks.
--
tejun
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