From: "H.J. Lu" <hjl.tools@gmail.com>
To: Dave Hansen <dave.hansen@intel.com>
Cc: Pavel Machek <pavel@ucw.cz>, Yu-cheng Yu <yu-cheng.yu@intel.com>,
"the arch/x86 maintainers" <x86@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
LKML <linux-kernel@vger.kernel.org>,
"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
linux-arch <linux-arch@vger.kernel.org>,
Linux API <linux-api@vger.kernel.org>,
Arnd Bergmann <arnd@arndb.de>, Andy Lutomirski <luto@kernel.org>,
Balbir Singh <bsingharora@gmail.com>,
Borislav Petkov <bp@alien8.de>,
Cyrill Gorcunov <gorcunov@gmail.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Eugene Syromiatnikov <esyr@redhat.com>,
Florian Weimer <fweimer@redhat.com>, Jann Horn <jannh@google.com>,
Jonathan Corbet <corbet@lwn.net>,
Kees Cook <keescook@chromium.org>,
Mike Kravetz <mike.kravetz@oracle.com>,
Nadav Amit <nadav.amit@gmail.com>,
Oleg Nesterov <oleg@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Randy Dunlap <rdunlap@infradead.org>,
"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
Vedvyas Shanbhogue <vedvyas.shanbhogue@intel.com>,
Dave Martin <Dave.Martin@arm.com>,
Weijiang Yang <weijiang.yang@intel.com>
Subject: Re: [PATCH v12 8/8] x86: Disallow vsyscall emulation when CET is enabled
Date: Fri, 18 Sep 2020 14:22:37 -0700 [thread overview]
Message-ID: <CAMe9rOqAmbRgGzUaA5ChGzeSqFVW524CJQ7Npe99BQtx-L_YBA@mail.gmail.com> (raw)
In-Reply-To: <4f93b106-53fc-40df-4c9b-c26490be24c8@intel.com>
On Fri, Sep 18, 2020 at 2:17 PM Dave Hansen <dave.hansen@intel.com> wrote:
>
> On 9/18/20 2:06 PM, H.J. Lu wrote:
> > On Fri, Sep 18, 2020 at 2:00 PM Pavel Machek <pavel@ucw.cz> wrote:
> >> On Fri 2020-09-18 12:32:57, Dave Hansen wrote:
> >>> On 9/18/20 12:23 PM, Yu-cheng Yu wrote:
> >>>> Emulation of the legacy vsyscall page is required by some programs
> >>>> built before 2013. Newer programs after 2013 don't use it.
> >>>> Disable vsyscall emulation when Control-flow Enforcement (CET) is
> >>>> enabled to enhance security.
> >>> How does this "enhance security"?
> >>>
> >>> What is the connection between vsyscall emulation and CET?
> >> Boom.
> >>
> >> We don't break compatibility by default, and you should not tell
> >> people to enable CET by default if you plan to do this.
> >>
> > Nothing will be broken. CET enabled applications don't use/need
> > vsyscall emulation.
>
> Hi H.J.,
>
> Could you explain your logic a bit more thoroughly, please?
Here is my CET slides for LPC 2020:
https://gitlab.com/cet-software/cet-smoke-test/-/wikis/uploads/09431a51248858e6f716a59065d732e2/CET-LPC-2020.pdf
which may have answers for most questions.
> I also suspect that Pavel was confused by your changelog where you said
> that you do this when "CET is enabled". Does enabled in this context mean:
> 1. Just CET support compiled in, or
> 2. Compiled in and on CET hardware, or
> 3. Compiled in to the kernel enabled in the app and running on CET
> hardware?
CET is enabled only in a process if
1. All components are CET enabled, and
2. CPU supports CET, and
3. Kernel supports CET.
--
H.J.
next prev parent reply other threads:[~2020-09-18 21:23 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-18 19:23 [PATCH v12 0/8] Control-flow Enforcement: Indirect Branch Tracking Yu-cheng Yu
2020-09-18 19:23 ` [PATCH v12 1/8] x86/cet/ibt: Add Kconfig option for user-mode " Yu-cheng Yu
2020-09-18 20:24 ` Randy Dunlap
2020-09-18 20:59 ` Pavel Machek
2020-09-18 21:08 ` H.J. Lu
2020-09-18 21:24 ` Pavel Machek
2020-09-18 21:36 ` H.J. Lu
2020-09-18 21:25 ` Yu, Yu-cheng
2020-09-18 21:40 ` Pavel Machek
2020-09-18 21:46 ` H.J. Lu
2020-09-18 22:03 ` Pavel Machek
2020-09-21 22:30 ` Yu, Yu-cheng
2020-09-21 22:41 ` Dave Hansen
2020-09-21 22:47 ` Yu, Yu-cheng
[not found] ` <9cf234db-d0f7-0466-be2c-afe04eb76759@intel.com>
2020-09-21 23:27 ` Yu, Yu-cheng
2020-09-21 22:52 ` Pavel Machek
2020-09-18 19:23 ` [PATCH v12 4/8] x86/cet/ibt: ELF header parsing for " Yu-cheng Yu
2020-09-18 19:23 ` [PATCH v12 5/8] x86/cet/ibt: Update arch_prctl functions " Yu-cheng Yu
2020-09-18 19:23 ` [PATCH v12 6/8] x86/vdso/32: Add ENDBR32 to __kernel_vsyscall entry point Yu-cheng Yu
2020-09-18 19:23 ` [PATCH v12 7/8] x86/vdso: Insert endbr32/endbr64 to vDSO Yu-cheng Yu
2020-09-18 19:23 ` [PATCH v12 8/8] x86: Disallow vsyscall emulation when CET is enabled Yu-cheng Yu
2020-09-18 19:32 ` Dave Hansen
2020-09-18 21:00 ` Pavel Machek
2020-09-18 21:06 ` H.J. Lu
2020-09-18 21:17 ` Dave Hansen
2020-09-18 21:22 ` H.J. Lu [this message]
2020-09-18 21:28 ` Dave Hansen
2020-09-18 21:21 ` Yu, Yu-cheng
2020-09-18 21:22 ` Pavel Machek
2020-09-19 0:11 ` Andy Lutomirski
2020-09-21 16:22 ` Yu, Yu-cheng
2020-09-21 22:37 ` Yu-cheng Yu
2020-09-21 23:48 ` Andy Lutomirski
2020-09-23 21:29 ` Sean Christopherson
[not found] ` <a2e872ef-5539-c7c1-49ca-95d590f3b92a@intel.com>
[not found] ` <e7c20f4c-23a0-4a34-3895-c4f60993ec41@intel.com>
2020-09-23 22:20 ` Yu, Yu-cheng
2020-09-23 22:47 ` Andy Lutomirski
2020-09-23 22:53 ` Dave Hansen
[not found] ` <b3defc91-1e8e-d0d5-2ac3-3861a7e3355c@intel.com>
2020-09-23 21:34 ` Andy Lutomirski
2020-09-23 22:07 ` Yu, Yu-cheng
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