linux-kernel - Re: [PATCH v5] x86/power/64: Fix kernel text mapping corruption during image restoration

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Message-ID: <20160630170237.GB3932@pd.tnic>
Date:	Thu, 30 Jun 2016 19:02:37 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Logan Gunthorpe <logang@...tatee.com>,
	Kees Cook <keescook@...omium.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	lkml <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Andy Lutomirski <luto@...nel.org>,
	Brian Gerst <brgerst@...il.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Stephen Smalley <sds@...ho.nsa.gov>
Subject: Re: [PATCH v5] x86/power/64: Fix kernel text mapping corruption
 during image restoration

On Thu, Jun 30, 2016 at 06:11:41PM +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Logan Gunthorpe reports that hibernation stopped working reliably for
> him after commit ab76f7b4ab23 (x86/mm: Set NX on gap between __ex_table
> and rodata).
> 
> That turns out to be a consequence of a long-standing issue with the
> 64-bit image restoration code on x86, which is that the temporary
> page tables set up by it to avoid page tables corruption when the
> last bits of the image kernel's memory contents are copied into
> their original page frames re-use the boot kernel's text mapping,
> but that mapping may very well get corrupted just like any other
> part of the page tables.  Of course, if that happens, the final
> jump to the image kernel's entry point will go to nowhere.

...

> Boris, please test it on the machine where we saw memory corruption with
> the previous versions if poss.

Looks good. 5 runs passed without a hiccup.

Reported-and-tested-by: Borislav Petkov <bp@...e.de>

-- 
Regards/Gruss,
    Boris.

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