linux-kernel - Re: [RFC PATCH 04/10 v2 ] x86/fpu: eager switch PKRU state

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: <20180919165719.iepvc7tg6aabp5mm@linutronix.de>
Date:   Wed, 19 Sep 2018 18:57:20 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Rik van Riel <riel@...riel.com>, linux-kernel@...r.kernel.org,
        x86@...nel.org, Andy Lutomirski <luto@...nel.org>,
        Radim Krčmář <rkrcmar@...hat.com>,
        kvm@...r.kernel.org, "Jason A. Donenfeld" <Jason@...c4.com>
Subject: Re: [RFC PATCH 04/10 v2 ] x86/fpu: eager switch PKRU state

On 2018-09-19 07:55:51 [+0200], Paolo Bonzini wrote:
> A kthread can do use_mm/unuse_mm.

indeed. The FPU struct for the kernel thread isn't valid / does not
contain the expected PKRU value. So loading the pkru value from the
struct FPU does not work as expected. We could set it to 0 for a kernel
thread so we don't end up with a random value.
If we want to get this usecase working then we would have to move pkru
value from FPU to mm_struct and consider it in use_mm(). Do we want
this?

> Paolo

Sebastian