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Subject: Re: [PATCH] x86/mm/pti: Move user W+X check into pti_finalize()
References: <1533727000-9172-1-git-send-email-joro@8bytes.org>
From: Dave Hansen <dave.hansen@intel.com>
Message-ID: <aee38579-3a53-3370-b22b-04603b6b65ce@intel.com>
Date: Wed, 8 Aug 2018 08:54:37 -0700
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To: Joerg Roedel <joro@8bytes.org>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@kernel.org>, "H . Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Linus Torvalds <torvalds@linux-foundation.org>, Andy Lutomirski <luto@kernel.org>, Josh Poimboeuf <jpoimboe@redhat.com>, Juergen Gross <jgross@suse.com>, Peter Zijlstra <peterz@infradead.org>, Borislav Petkov <bp@alien8.de>, Jiri Kosina <jkosina@suse.cz>, Boris Ostrovsky <boris.ostrovsky@oracle.com>, Brian Gerst <brgerst@gmail.com>, David Laight <David.Laight@aculab.com>, Denys Vlasenko <dvlasenk@redhat.com>, Eduardo Valentin <eduval@amazon.com>, Greg KH <gregkh@linuxfoundation.org>, Will Deacon <will.deacon@arm.com>, aliguori@amazon.com, daniel.gruss@iaik.tugraz.at, hughd@google.com, keescook@google.com, Andrea Arcangeli <aarcange@redhat.com>, Waiman Long <llong@redhat.com>, Pavel Machek <pavel@ucw.cz>, "David H . Gutteridge" <dhgutteridge@sympatico.ca>, jroedel@suse.de

On 08/08/2018 04:16 AM, Joerg Roedel wrote:
> But with CONFIG_DEBUG_WX enabled, the user page-table is
> already checked in mark_readonly() for insecure mappings.
> This causes false-positive warnings, because the user
> page-table did not get the updated mappings yet.

One bit of information missing from the changelog: Could you clarify how
there are any entries in the user page tables for the code to complain?
Before pti_init(), I would have expected the user page tables to be empty.

That causes a different problem, but it would not have resulted in
warnings, so I think I'm missing something.