linux-kernel - RE: [PATCH V4 3/3] x86/efi: Introduce EFI_PAGE_FAULT

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: <FFF73D592F13FD46B8700F0A279B802F485BA5C1@ORSMSX114.amr.corp.intel.com>
Date:   Fri, 7 Sep 2018 18:23:48 +0000
From:   "Prakhya, Sai Praneeth" <sai.praneeth.prakhya@...el.com>
To:     Peter Zijlstra <peterz@...radead.org>
CC:     "linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "Neri, Ricardo" <ricardo.neri@...el.com>,
        "matt@...eblueprint.co.uk" <matt@...eblueprint.co.uk>,
        Al Stone <astone@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Ingo Molnar <mingo@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Bhupesh Sharma <bhsharma@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: RE: [PATCH V4 3/3] x86/efi: Introduce EFI_PAGE_FAULT_HANDLER

> > There may exist some buggy UEFI firmware implementations that might
> > access efi regions other than EFI_RUNTIME_SERVICES_<CODE/DATA> even
> > after the kernel has assumed control of the platform. This violates
> > UEFI specification.
> >
> > If selected, this debug option will print a warning message if the
> > UEFI firmware tries to access any memory region which it shouldn't.
> > Along with the warning, the efi page fault handler will also try to
> > recover from the page fault triggered by the firmware so that the
> > machine doesn't hang.
> 
> Why make this optional?

I made it as a config option in RFC because the page fault handler was 
complicated and touching many parts (it had lots of code change and I didn't want 
to break any existing functionality). Now that it's simple, I don't think we need 
the config option.

Without efi page fault handler, any page fault caused by firmware should panic 
kernel but with this patch I think we are just improving existing condition (ideally).

So, if Thomas, Ingo, Andy, Ard and Boris are ok.. I will make it as default (i.e. without
config).

Regards,
Sai