linux-kernel - Re: [PATCH v4 10/29] x86/die: Don't try to recover from an OOPS on a non-default stack

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Date:	Sun, 3 Jul 2016 11:40:38 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Josh Poimboeuf <jpoimboe@...hat.com>
Cc:	Andy Lutomirski <luto@...nel.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	Nadav Amit <nadav.amit@...il.com>,
	Kees Cook <keescook@...omium.org>,
	Brian Gerst <brgerst@...il.com>,
	"kernel-hardening@...ts.openwall.com" 
	<kernel-hardening@...ts.openwall.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jann Horn <jann@...jh.net>,
	Heiko Carstens <heiko.carstens@...ibm.com>
Subject: Re: [PATCH v4 10/29] x86/die: Don't try to recover from an OOPS on a
 non-default stack

On Sat, Jul 02, 2016 at 01:34:51PM -0500, Josh Poimboeuf wrote:
> The existing 'object_is_on_stack()' can probably be used:
> 
> 	if (!object_is_on_stack(current_top_of_stack()))
> 		panic("...");
> 
> Though that function isn't quite accurately named.  It should really
> have 'task_stack' in its name, like 'object_is_on_task_stack()'.  Or
> even better, something more concise like 'on_task_stack()'.

So I'm obviously missing something here:

object_is_on_stack() uses task_stack_page(current) -> task_struct.stack
while current_stack_pointer() reads %rsp directly.

I'm guessing %rsp and task_struct.stack are in sync?

-- 
Regards/Gruss,
    Boris.

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