linux-kernel - Re: [EXTERNAL] [PATCH 1/9] x86/kexec: Disable global pages before writing to control page

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]

Message-ID: <ca888eb1-056c-436e-9471-91dbf2f6abf4@intel.com>
Date: Tue, 17 Dec 2024 07:06:03 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: David Woodhouse <dwmw2@...radead.org>,
 "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
 x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
 Eric Biederman <ebiederm@...ssion.com>,
 Sourabh Jain <sourabhjain@...ux.ibm.com>,
 Hari Bathini <hbathini@...ux.ibm.com>, Michael Ellerman
 <mpe@...erman.id.au>, Thomas Zimmermann <tzimmermann@...e.de>,
 Andrew Morton <akpm@...ux-foundation.org>, Baoquan He <bhe@...hat.com>,
 Yuntao Wang <ytcoode@...il.com>, David Kaplan <david.kaplan@....com>,
 Tao Liu <ltao@...hat.com>, Kai Huang <kai.huang@...el.com>,
 Ard Biesheuvel <ardb@...nel.org>, Josh Poimboeuf <jpoimboe@...nel.org>,
 Breno Leitao <leitao@...ian.org>, Wei Yang <richard.weiyang@...il.com>,
 Rong Xu <xur@...gle.com>, Thomas Weißschuh
 <thomas.weissschuh@...utronix.de>, linux-kernel@...r.kernel.org,
 kexec@...ts.infradead.org, Simon Horman <horms@...nel.org>,
 Dave Young <dyoung@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
 bsz@...zon.de, nathan@...nel.org
Subject: Re: [EXTERNAL] [PATCH 1/9] x86/kexec: Disable global pages before
 writing to control page

On 12/17/24 06:56, David Woodhouse wrote:
>> Anyway, I think we can leave the belt-and-suspenders programming in this
>> case. A comment wouldn't hurt I guess.
> I'm a little lost. In this case I don't see belt-and-suspenders
> programming. We're not loading CR3 after clearing CR4.PGE just to be
> paranoid about making really really sure the TLB is flushed.
> 
> We're loading CR3 because we're switching from the kernel's page tables
> to the new identity mapping set up for the relocate_kernel environment.

Yes, agreed, that's another reason the CR3 write must stay. I hadn't
even considered that part yet honestly.