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Date: Wed, 29 Mar 2017 15:38:43 -0700
From: Andy Lutomirski <luto@...capital.net>
To: Kees Cook <keescook@...omium.org>
Cc: "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>,
Mark Rutland <mark.rutland@....com>, Andy Lutomirski <luto@...nel.org>, Hoeun Ryu <hoeun.ryu@...il.com>,
PaX Team <pageexec@...email.hu>, Emese Revfy <re.emese@...il.com>,
Russell King <linux@...linux.org.uk>, X86 ML <x86@...nel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap()
On Wed, Mar 29, 2017 at 11:15 AM, Kees Cook <keescook@...omium.org> wrote:
> Based on PaX's x86 pax_{open,close}_kernel() implementation, this
> allows HAVE_ARCH_RARE_WRITE to work on x86.
>
> +
> +static __always_inline unsigned long __arch_rare_write_begin(void)
> +{
> + unsigned long cr0;
> +
> + preempt_disable();
This looks wrong. DEBUG_LOCKS_WARN_ON(!irqs_disabled()) would work,
as would local_irq_disable(). There's no way that just disabling
preemption is enough.
(Also, how does this interact with perf nmis?)
--Andy
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