linux-kernel - Re: [PATCH 05/23] x86, kaiser: unmap kernel from userspace page tables (core patch)

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Date:   Fri, 5 Jan 2018 22:06:50 -0800
From:   Dave Hansen <dave.hansen@...ux.intel.com>
To:     Hanjun Guo <guohanjun@...wei.com>, Jiri Kosina <jikos@...nel.org>
Cc:     Yisheng Xie <xieyisheng1@...wei.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, richard.fellner@...dent.tugraz.at,
        moritz.lipp@...k.tugraz.at, daniel.gruss@...k.tugraz.at,
        michael.schwarz@...k.tugraz.at, luto@...nel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        keescook@...gle.com, hughd@...gle.com, x86@...nel.org,
        Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: [PATCH 05/23] x86, kaiser: unmap kernel from userspace page
 tables (core patch)

On 01/05/2018 08:54 PM, Hanjun Guo wrote:
> Do you mean NX bit will be brought back later? I'm asking this because
> I tested this patch which it fixed the boot panic issue but the system
> will hang when rebooting the system, because rebooting will also call efi
> then panic as NS bit is set.

Wow, you're running a lot of very lighly-used code paths!  You actually
found a similar but totally separate issue from what I gather.  Thank
you immensely for the quick testing and bug reports!

Could you test the attached fix?

For those playing along at home, I think this will end up being needed
for 4.15 and probably all the backports.  I want to see if it works
before I submit it for real, though.

View attachment "pti-tboot-fix.patch" of type "text/x-patch" (1351 bytes)