linux-kernel - Re: [Resend][PATCH] x86/power/64: Always create temporary identity mapping correctly

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Message-ID: <alpine.LNX.2.00.1608092119260.22028@cbobk.fhfr.pm>
Date:	Tue, 9 Aug 2016 22:02:25 +0200 (CEST)
From:	Jiri Kosina <jikos@...nel.org>
To:	"Rafael J. Wysocki" <rafael@...nel.org>
cc:	Thomas Garnier <thgarnie@...gle.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Linux PM list <linux-pm@...r.kernel.org>,
	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Yinghai Lu <yinghai@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H . Peter Anvin" <hpa@...or.com>,
	Kees Cook <keescook@...omium.org>, Pavel Machek <pavel@....cz>,
	Kernel Hardening <kernel-hardening@...ts.openwall.com>,
	Borislav Petkov <bpetkov@...e.de>
Subject: Re: [Resend][PATCH] x86/power/64: Always create temporary identity
 mapping correctly

On Tue, 9 Aug 2016, Rafael J. Wysocki wrote:

> I have a murky suspicion, but it is really weird.  Namely, what if
> restore_jump_address in set_up_temporary_text_mapping() happens to be
> covered by the restore kernel's identity mapping?  Then, the image
> kernel's entry point may get overwritten by something else in
> core_restore_code().

So this made me to actually test a scenario where I'd suspend a kernel 
that's known-broken (i.e. contains 021182e52fe), and then have it resumed 
by a kernel that has 021182e52fe reverted. It resumed successfully.

Just a datapoint.

-- 
Jiri Kosina
SUSE Labs