kernel-hardening - Re: [RFC V2 0/6] add more kernel pointer filter options

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Message-ID: <CAErSpo4JfDPUnK4LhU=5GN7KVhWRatcEnu5VCsMwrEh6f9St5w@mail.gmail.com>
Date: Thu, 5 Oct 2017 08:55:26 -0500
From: Bjorn Helgaas <bhelgaas@...gle.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: "Roberts, William C" <william.c.roberts@...el.com>, Tejun Heo <tj@...nel.org>, 
	Jordan Glover <Golden_Miller83@...tonmail.ch>, "Tobin C. Harding" <me@...in.cc>, 
	Greg KH <gregkh@...uxfoundation.org>, Petr Mladek <pmladek@...e.com>, 
	Joe Perches <joe@...ches.com>, Ian Campbell <ijc@...lion.org.uk>, 
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>, 
	"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, 
	Catalin Marinas <catalin.marinas@....com>, Will Deacon <will.deacon@....com>, 
	Steven Rostedt <rostedt@...dmis.org>, Chris Fries <cfries@...gle.com>, 
	Dave Weinstein <olorin@...gle.com>
Subject: Re: [RFC V2 0/6] add more kernel pointer filter options

On Wed, Oct 4, 2017 at 7:09 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
> On Wed, Oct 4, 2017 at 4:52 PM, Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
>>
>> It also shows
>>
>>     software IO TLB [mem PA-PB] (64MB) mapped at [VA-VB]
>>
>> for example.  And THIS IS IMPORTANT! The physical address is shown
>> with "%#010llx".
>
> Oh, and I added Tejun for the percpu printout, but didn't add Bjorn
> for this one.
>
> Like the percpu one, I suspect that this pr_info() isn't really
> important enough to stay, and while it doesn't sound nearly as
> interesting as the percpu virtual address to an attacker, it probably
> isn't important enough to leak kernel (and hardware) data for.
>
> Bjorn?

My only interest in the "software IO TLB" message was to make the
style match other similar things; I personally don't care whether this
message exists at all.

I haven't seen the whole series, but I do hope %pR remains useful.  We
use it often to analyze PCI BAR assignment issues.

Bjorn

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