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[209.85.167.54]) by smtp.gmail.com with ESMTPSA id l13sm43739ljj.96.2019.04.17.16.18.31 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 17 Apr 2019 16:18:32 -0700 (PDT) Received: by mail-lf1-f54.google.com with SMTP id h18so78925lfj.11 for ; Wed, 17 Apr 2019 16:18:31 -0700 (PDT) X-Received: by 2002:ac2:598b:: with SMTP id w11mr21120489lfn.62.1555543110507; Wed, 17 Apr 2019 16:18:30 -0700 (PDT) MIME-Version: 1.0 References: <20190417161042.GA43453@gmail.com> <20190417170918.GA68678@gmail.com> <56A175F6-E5DA-4BBD-B244-53B786F27B7F@gmail.com> <20190417172632.GA95485@gmail.com> <063753CC-5D83-4789-B594-019048DE22D9@gmail.com> In-Reply-To: From: Linus Torvalds Date: Wed, 17 Apr 2019 16:18:18 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [RFC PATCH v9 03/13] mm: Add support for eXclusive Page Frame Ownership (XPFO) To: Thomas Gleixner Cc: Nadav Amit , Ingo Molnar , Khalid Aziz , juergh@gmail.com, Tycho Andersen , jsteckli@amazon.de, keescook@google.com, Konrad Rzeszutek Wilk , Juerg Haefliger , deepa.srinivasan@oracle.com, chris.hyser@oracle.com, tyhicks@canonical.com, David Woodhouse , Andrew Cooper , jcm@redhat.com, Boris Ostrovsky , iommu , X86 ML , linux-arm-kernel@lists.infradead.org, "open list:DOCUMENTATION" , Linux List Kernel Mailing , Linux-MM , LSM List , Khalid Aziz , Andrew Morton , Andy Lutomirski , Peter Zijlstra , Dave Hansen , Borislav Petkov , "H. Peter Anvin" , Arjan van de Ven , Greg Kroah-Hartman Content-Type: multipart/alternative; boundary="00000000000088f1ef0586c21a38" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: --00000000000088f1ef0586c21a38 Content-Type: text/plain; charset="UTF-8" On Wed, Apr 17, 2019, 14:20 Thomas Gleixner wrote: > > It's not necessarily a W+X issue. The user space text is mapped in the > kernel as well and even if it is mapped RX then this can happen. So any > kernel mappings of user space text need to be mapped NX! With SMEP, user space pages are always NX. I really think SM[AE]P is something we can already take for granted. People who have old CPU's workout it are simply not serious about security anyway. There is no point in saying "we can do it badly in software". Linus > --00000000000088f1ef0586c21a38 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable


On Wed, Apr 17, 2019, 14:20 Thomas Gleixner <tglx@linutronix.de> wrote:
=

It's not necessarily a W+X issue. The user space text is mapped in the<= br> kernel as well and even if it is mapped RX then this can happen. So any
kernel mappings of user space text need to be mapped NX!
=

With SMEP, user space p= ages are always NX.

I re= ally think SM[AE]P is something we can already take for granted. People who= have old CPU's workout it are simply not serious about security anyway= . There is no point in saying "we can do it badly in software".

=C2=A0 =C2=A0 =C2=A0 =C2= =A0Linus
=C2=A0
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