linux-kernel - Re: [patch V2 1/5] x86/kaiser: Respect disabled CPU features

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:   Mon, 27 Nov 2017 07:31:37 -0500
From:   Brian Gerst <brgerst@...il.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Rik van Riel <riel@...hat.com>,
        Daniel Gruss <daniel.gruss@...k.tugraz.at>,
        Hugh Dickins <hughd@...gle.com>,
        Kees Cook <keescook@...gle.com>, Linux-MM <linux-mm@...ck.org>,
        michael.schwarz@...k.tugraz.at, moritz.lipp@...k.tugraz.at,
        richard.fellner@...dent.tugraz.at
Subject: Re: [patch V2 1/5] x86/kaiser: Respect disabled CPU features

On Mon, Nov 27, 2017 at 6:47 AM, Thomas Gleixner <tglx@...utronix.de> wrote:
> On Mon, 27 Nov 2017, Peter Zijlstra wrote:
>> On Mon, Nov 27, 2017 at 12:14:04AM +0100, Thomas Gleixner wrote:
>> > PAGE_NX and PAGE_GLOBAL might be not supported or disabled on the command
>> > line, but KAISER sets them unconditionally.
>>
>> So KAISER is x86_64 only, right? AFAIK there is no x86_64 without NX
>> support. So would it not make sense to mandate NX for KAISER?, that is
>> instead of making "noexec" + KAISER work, make "noexec" kill KAISER +
>> emit a warning.
>
> OTOH, disabling NX is a simple way to verify that DEBUG_WX works correctly
> also on the shadow maps.
>
> But surely we can drop the PAGE_GLOBAL thing, as all 64bit systems have it.

I seem to recall that some virtualized environments (maybe Xen?) don't
support global pages.

--
Brian Gerst