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From: Ingo Molnar <mingo@kernel.org>
To: Kees Cook <keescook@chromium.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
	"kernel-hardening@lists.openwall.com"
	<kernel-hardening@lists.openwall.com>,
	Ingo Molnar <mingo@redhat.com>,
	LKML <linux-kernel@vger.kernel.org>,
	"x86@kernel.org" <x86@kernel.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
	Jeremy Fitzhardinge <jeremy@goop.org>,
	Marcelo Tosatti <mtosatti@redhat.com>,
	Alex Shi <alex.shi@intel.com>,
	Borislav Petkov <borislav.petkov@amd.com>,
	Alexander Duyck <alexander.h.duyck@intel.com>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	"xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>,
	"virtualization@lists.linux-foundation.org"
	<virtualization@lists.linux-foundation.org>,
	Dan Rosenberg <drosenberg@vsecurity.com>,
	Julien Tinnes <jln@google.com>, Will Drewry <wad@chromium.org>,
	Eric Northup <digitaleric@google.com>
Subject: Re: [kernel-hardening] Re: [PATCH] x86: make IDT read-only
Date: Wed, 10 Apr 2013 11:41:35 +0200	[thread overview]
Message-ID: <20130410094135.GD24443@gmail.com> (raw)
In-Reply-To: <CAGXu5jJNG4o+_-kk=A2AfSRwyQE0pgaQh7YpSjnD_fB-s7U+wA@mail.gmail.com>


* Kees Cook <keescook@chromium.org> wrote:

> > That's the area in which we just map 1:1 to memory.  Anything allocated with 
> > e.g. kmalloc() ends up with those addresses.
> 
> Ah-ha! Yes, I see now when comparing the debug/kernel_page_tables reports. It's 
> just the High Kernel Mapping that we care about. Addresses outside that range 
> are less of a leak. Excellent, then GDT may not be a problem. Whew.

It's still an infoleak to worry about: any function pointers nearby matter, and 
the x86 GDT is obviously full of useful and highly privilege-relevant function 
pointers ...

I have no objections against read-only mapping the GDT as well.

Thanks,

	Ingo

WARNING: multiple messages have this Message-ID (diff)
From: Ingo Molnar <mingo@kernel.org>
To: Kees Cook <keescook@chromium.org>
Cc: Alexander Duyck <alexander.h.duyck@intel.com>,
	Alex Shi <alex.shi@intel.com>,
	Jeremy Fitzhardinge <jeremy@goop.org>,
	Will Drewry <wad@chromium.org>, Julien Tinnes <jln@google.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
	"kernel-hardening@lists.openwall.com"
	<kernel-hardening@lists.openwall.com>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	Dan Rosenberg <drosenberg@vsecurity.com>,
	"x86@kernel.org" <x86@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Borislav Petkov <borislav.petkov@amd.com>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	"virtualization@lists.linux-foundation.org"
	<virtualization@lists.linux-foundation.org>,
	"xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>
Subject: Re: [kernel-hardening] Re: [PATCH] x86: make IDT read-only
Date: Wed, 10 Apr 2013 11:41:35 +0200	[thread overview]
Message-ID: <20130410094135.GD24443@gmail.com> (raw)
In-Reply-To: <CAGXu5jJNG4o+_-kk=A2AfSRwyQE0pgaQh7YpSjnD_fB-s7U+wA@mail.gmail.com>


* Kees Cook <keescook@chromium.org> wrote:

> > That's the area in which we just map 1:1 to memory.  Anything allocated with 
> > e.g. kmalloc() ends up with those addresses.
> 
> Ah-ha! Yes, I see now when comparing the debug/kernel_page_tables reports. It's 
> just the High Kernel Mapping that we care about. Addresses outside that range 
> are less of a leak. Excellent, then GDT may not be a problem. Whew.

It's still an infoleak to worry about: any function pointers nearby matter, and 
the x86 GDT is obviously full of useful and highly privilege-relevant function 
pointers ...

I have no objections against read-only mapping the GDT as well.

Thanks,

	Ingo

  parent reply	other threads:[~2013-04-10  9:41 UTC|newest]

Thread overview: 83+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-04-08 22:43 [kernel-hardening] [PATCH] x86: make IDT read-only Kees Cook
2013-04-08 22:43 ` Kees Cook
2013-04-08 22:43 ` Kees Cook
2013-04-08 22:47 ` [kernel-hardening] " H. Peter Anvin
2013-04-08 22:47   ` H. Peter Anvin
2013-04-08 22:47   ` H. Peter Anvin
2013-04-08 22:55   ` [kernel-hardening] " Kees Cook
2013-04-08 22:55     ` Kees Cook
2013-04-08 22:55     ` Kees Cook
2013-04-08 22:48 ` [kernel-hardening] " H. Peter Anvin
2013-04-08 22:48   ` H. Peter Anvin
2013-04-08 22:48   ` H. Peter Anvin
2013-04-09  9:23   ` Thomas Gleixner
2013-04-09  9:23   ` [kernel-hardening] " Thomas Gleixner
2013-04-09  9:23     ` Thomas Gleixner
2013-04-09 18:22     ` [kernel-hardening] " Kees Cook
2013-04-09 18:22       ` Kees Cook
2013-04-09 18:26       ` H. Peter Anvin
2013-04-09 18:26         ` H. Peter Anvin
2013-04-09 18:31         ` Kees Cook
2013-04-09 18:31           ` Kees Cook
2013-04-09 18:39           ` H. Peter Anvin
2013-04-09 18:39             ` H. Peter Anvin
2013-04-09 18:46             ` Kees Cook
2013-04-09 18:46               ` Kees Cook
2013-04-09 18:50               ` H. Peter Anvin
2013-04-09 18:50                 ` H. Peter Anvin
2013-04-09 18:53                 ` Kees Cook
2013-04-09 18:53                   ` Kees Cook
2013-04-09 18:54               ` Eric Northup
2013-04-09 18:54                 ` Eric Northup
2013-04-09 18:59                 ` H. Peter Anvin
2013-04-09 18:59                   ` H. Peter Anvin
2013-04-10  0:43                 ` [kernel-hardening] Readonly GDT H. Peter Anvin
2013-04-10  0:43                   ` H. Peter Anvin
2013-04-10  0:43                   ` H. Peter Anvin
2013-04-10  0:53                   ` [kernel-hardening] " Steven Rostedt
2013-04-10  0:53                     ` Steven Rostedt
2013-04-10  0:53                     ` Steven Rostedt
2013-04-10  0:58                     ` [kernel-hardening] " H. Peter Anvin
2013-04-10  0:58                       ` H. Peter Anvin
2013-04-10  0:58                       ` H. Peter Anvin
2013-04-10  9:42                   ` [kernel-hardening] Re: [Xen-devel] " Jan Beulich
2013-04-10  9:42                     ` Jan Beulich
2013-04-10  9:42                     ` Jan Beulich
2013-04-10 14:16                     ` [kernel-hardening] " H. Peter Anvin
2013-04-10 14:16                       ` H. Peter Anvin
2013-04-10 14:16                       ` H. Peter Anvin
2013-04-10 18:28                     ` [kernel-hardening] " H. Peter Anvin
2013-04-10 18:28                       ` H. Peter Anvin
2013-04-10  9:41               ` Ingo Molnar [this message]
2013-04-10  9:41                 ` [kernel-hardening] Re: [PATCH] x86: make IDT read-only Ingo Molnar
2013-04-10  0:03       ` H. Peter Anvin
2013-04-10  0:03         ` H. Peter Anvin
2013-04-10  9:52         ` Ingo Molnar
2013-04-10  9:52           ` Ingo Molnar
2013-04-09  9:45   ` Eric W. Biederman
2013-04-09  9:45     ` Eric W. Biederman
2013-04-09  9:45     ` Eric W. Biederman
2013-04-10  9:57     ` [kernel-hardening] " Ingo Molnar
2013-04-10  9:57       ` Ingo Molnar
2013-04-10  9:57       ` Ingo Molnar
2013-04-10 10:40       ` [kernel-hardening] " Eric W. Biederman
2013-04-10 10:40         ` Eric W. Biederman
2013-04-10 10:40         ` Eric W. Biederman
2013-04-10 16:31         ` [kernel-hardening] " Eric Northup
2013-04-10 16:31           ` Eric Northup
2013-04-10 16:31           ` Eric Northup
2013-04-10 16:48           ` [kernel-hardening] " H. Peter Anvin
2013-04-10 16:48             ` H. Peter Anvin
2013-04-10 16:48             ` H. Peter Anvin
2013-04-08 22:56 ` Maciej W. Rozycki
2013-04-08 22:56 ` [kernel-hardening] " Maciej W. Rozycki
2013-04-08 22:56   ` Maciej W. Rozycki
2013-04-08 23:00   ` [kernel-hardening] " Kees Cook
2013-04-08 23:00     ` Kees Cook
2013-04-08 23:00     ` Kees Cook
2013-04-08 23:05   ` [kernel-hardening] " Kees Cook
2013-04-08 23:05     ` Kees Cook
2013-04-08 23:05     ` Kees Cook
2013-04-08 23:42     ` [kernel-hardening] " Maciej W. Rozycki
2013-04-08 23:42       ` Maciej W. Rozycki
2013-04-08 23:42       ` Maciej W. Rozycki

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