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From: Ian Campbell <ijc@hellion.org.uk>
To: Greg KH <gregkh@linuxfoundation.org>,
	kernel-hardening@lists.openwall.com,
	Petr Mladek <pmladek@suse.com>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: linux-kernel@vger.kernel.org,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	William Roberts <william.c.roberts@intel.com>,
	Chris Fries <cfries@google.com>,
	Dave Weinstein <olorin@google.com>
Subject: Re: [kernel-hardening] [RFC 3/6] lib: vsprintf: physical address kernel pointer filtering options
Date: Sat, 06 May 2017 11:48:36 +0100	[thread overview]
Message-ID: <1494067716.4633.8.camel@hellion.org.uk> (raw)
In-Reply-To: <20170506040720.GD32707@kroah.com>

On Fri, 2017-05-05 at 21:07 -0700, Greg KH wrote:
> From: Dave Weinstein <olorin@google.com>
> 
> Add the kptr_restrict setting of 4 which results in %pa and
> %p[rR] values being replaced by zeros.

Given that '%pa' is:
 * - 'a[pd]' For address types [p] phys_addr_t, [d] dma_addr_t and derivatives
 *           (default assumed to be phys_addr_t, passed by reference)

what is the thread model which hiding physical addresses from attackers
protects against? I can see why virtual addresses would be obviously
dangerous but physical addresses seem less obvious and I didn't see it
spelled out in any of the commit messages or added comments in the
thread.

I think a comment somewhere would be useful for people who are trying
to decide if they should use %pa vs %paP etc.

Ian.

  reply	other threads:[~2017-05-06 10:49 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-05-06  4:06 [RFC 00/06] printk: add more new kernel pointer filter options Greg KH
2017-05-06  4:06 ` [kernel-hardening] " Greg KH
2017-05-06  4:06 ` [RFC 1/6] lib: vsprintf: additional kernel pointer filtering options Greg KH
2017-05-06  4:06   ` [kernel-hardening] " Greg KH
2017-05-16 11:58   ` Petr Mladek
2017-05-16 11:58     ` [kernel-hardening] " Petr Mladek
2017-05-18 14:12     ` Greg KH
2017-05-18 14:12       ` [kernel-hardening] " Greg KH
2017-05-06  4:07 ` [RFC 2/6] lib: vsprintf: whitelist stack traces Greg KH
2017-05-06  4:07   ` [kernel-hardening] " Greg KH
2017-05-06  4:07 ` [RFC 3/6] lib: vsprintf: physical address kernel pointer filtering options Greg KH
2017-05-06  4:07   ` [kernel-hardening] " Greg KH
2017-05-06 10:48   ` Ian Campbell [this message]
2017-05-06  4:07 ` [RFC 4/6] lib: vsprintf: default kptr_restrict to the maximum value Greg KH
2017-05-06  4:07   ` [kernel-hardening] " Greg KH
2017-05-06  4:07 ` [RFC 5/6] lib: vsprintf: Add "%paP", "%padP" options Greg KH
2017-05-06  4:07   ` [kernel-hardening] " Greg KH
2017-05-06  4:42   ` Joe Perches
2017-05-06  4:42     ` [kernel-hardening] " Joe Perches
2017-05-06  5:00     ` Greg KH
2017-05-06  5:00       ` [kernel-hardening] " Greg KH
2017-05-16 14:41   ` Petr Mladek
2017-05-16 14:41     ` [kernel-hardening] " Petr Mladek
2017-05-18 14:12     ` Greg KH
2017-05-18 14:12       ` [kernel-hardening] " Greg KH
2017-05-06  4:07 ` [RFC 6/6] drivers: uio: Un-restrict sysfs pointers for UIO Greg KH
2017-05-06  4:07   ` [kernel-hardening] " Greg KH
2017-05-11  1:37 ` [RFC 00/06] printk: add more new kernel pointer filter options Sergey Senozhatsky
2017-05-11  1:37   ` [kernel-hardening] " Sergey Senozhatsky
2017-05-16 21:36   ` Roberts, William C
2017-05-16 21:36     ` [kernel-hardening] " Roberts, William C
2017-05-18 14:13     ` Greg KH
2017-05-18 14:13       ` [kernel-hardening] " Greg KH
2017-05-19 20:25       ` Roberts, William C
2017-05-19 20:25         ` [kernel-hardening] " Roberts, William C

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