From: "Yu, Yu-cheng" <yu-cheng.yu@intel.com>
To: Pavel Machek <pavel@ucw.cz>, Dave Hansen <dave.hansen@intel.com>
Cc: x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
linux-mm@kvack.org, linux-arch@vger.kernel.org,
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>,
"H.J. Lu" <hjl.tools@gmail.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 14:21:10 -0700 [thread overview]
Message-ID: <862eef02-eba2-e13f-ed67-f915f749ebca@intel.com> (raw)
In-Reply-To: <20200918210026.GC4304@duo.ucw.cz>
On 9/18/2020 2:00 PM, Pavel Machek 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.
I would revise the wording if there is another version. What this patch
does is:
If an application is compiled for CET and the system supports it, then
the application cannot do vsyscall emulation. Earlier we allow the
emulation, and had a patch that fixes the shadow stack and endbr for the
emulation code. Since newer programs mostly do no do the emulation, we
changed the patch do block it when attempted.
This patch would not block any legacy applications or any applications
on older machines.
Yu-cheng
next prev parent reply other threads:[~2020-09-18 21:21 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
2020-09-18 21:28 ` Dave Hansen
2020-09-18 21:21 ` Yu, Yu-cheng [this message]
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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