linux-kernel - Re: [PATCHv6 00/16] x86/tdx: Add kexec support

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] [day] [month] [year] [list]

Message-ID: <ZbpmBulaR7eft/CE@MiWiFi-R3L-srv>
Date: Wed, 31 Jan 2024 23:23:50 +0800
From: Baoquan He <bhe@...hat.com>
To: "Huang, Kai" <kai.huang@...el.com>,
	Nikolay Borisov <nik.borisov@...e.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	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" <x86@...nel.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	"Hunter, Adrian" <adrian.hunter@...el.com>,
	Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>,
	"Reshetova, Elena" <elena.reshetova@...el.com>,
	"Nakajima, Jun" <jun.nakajima@...el.com>,
	"Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
	Tom Lendacky <thomas.lendacky@....com>,
	"Kalra, Ashish" <ashish.kalra@....com>,
	Sean Christopherson <seanjc@...gle.com>,
	"kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
	"linux-coco@...ts.linux.dev" <linux-coco@...ts.linux.dev>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv6 00/16] x86/tdx: Add kexec support

On 01/31/24 at 01:07pm, Huang, Kai wrote:
> > > Runtime disabling kexec looks better than at cmpile time, esp for
> > > distros. While from above patch, making using of kexec_load_disabled
> > > to achive the runtime disabling may not be so good. Because we have a
> > > front door to enable it through:
> > >
> > > /proc/sys/kernel/kexec_load_disabled
> > 
> > AFAIU it can't be enabled via this sysctl because the handler for it expects
> > only 1 to be written to it:
> > 
> >       2                 .proc_handler   = proc_dointvec_minmax,
> > 
> >       1                 .extra1         = SYSCTL_ONE,
> > 
> >    994                  .extra2         = SYSCTL_ONE,
> > 
> 
> This is also my understanding.  
> 
> The documentation also says once it is turned to disable we cannot turn back again:
> 
> kexec_load_disable
> ===================
> 
> A toggle indicating if the syscalls ``kexec_load`` and
> ``kexec_file_load`` have been disabled.
> This value defaults to 0 (false: ``kexec_*load`` enabled), but can be
> set to 1 (true: ``kexec_*load`` disabled).
> Once true, kexec can no longer be used, and the toggle cannot be set
> back to false.

you are quite right, I have never noticed this, thanks.

Then then mentioned patch looks good to me.