linux-kernel - Re: [RFC PATCH] x86: Make sure verify

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 2 Mar 2016 20:50:53 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Brian Gerst <brgerst@...il.com>, X86 ML <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Tom Lendacky <thomas.lendacky@....com>
Subject: Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack

On Wed, Mar 02, 2016 at 10:39:05AM -0800, H. Peter Anvin wrote:
> Well, we definitely should use %rip-relative addressing if we can.

Right you are.

> However, even so I believe this breaks if the kernel is loaded anywhere
> but its default load address.  I think we need to do something like:
> 
> 	movq	stack_start(%rip), %rax
> 	leaq	__START_KERNEL_map(%rip), %rdx
> 	subq	%rdx, %rax
> 	movq	%rax, %rsp
> 
> The use of temporary registers avoids clobbering a valid stack pointer
> for even a single instruction if we are given one.

Yeah, we should be prudent and make this as sturdy as possible. I did this:

CONFIG_PHYSICAL_START=0x100beef

and it aligned startup_64 up to ffffffff82000000. It seems to boot fine
in kvm. But better safe than sorry.

Thanks.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.