linux-kernel - Re: [PATCH] arm: Use kernel mm when updating section permissions

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Date:	Fri, 6 Nov 2015 20:46:41 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Laura Abbott <labbott@...hat.com>
Cc:	Kees Cook <keescook@...omium.org>,
	Laura Abbott <labbott@...oraproject.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux-MM <linux-mm@...ck.org>
Subject: Re: [PATCH] arm: Use kernel mm when updating section permissions

On Fri, Nov 06, 2015 at 10:44:32AM -0800, Laura Abbott wrote:
> with my test patch. I think setting both current->active_mm and &init_mm
> is sufficient. Maybe explicitly setting swapper_pg_dir would be cleaner?

Please, stop thinking like this.  If you're trying to change the kernel
section mappings after threads have been spawned, you need to change
them for _all_ threads, which means you need to change them for every
page table that's in existence at that time - you can't do just one
table and hope everyone updates, it doesn't work like that.

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