From: Andy Lutomirski <luto@amacapital.net>
To: "H.J. Lu" <hjl.tools@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>,
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>, Pavel Machek <pavel@ucw.cz>,
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>,
x86-patch-review@intel.com
Subject: Re: [RFC PATCH v9 01/27] Documentation/x86: Add CET description
Date: Mon, 9 Mar 2020 18:21:01 -0700 [thread overview]
Message-ID: <E7E7A2AE-500A-4817-B00A-BE419E89C6F9@amacapital.net> (raw)
In-Reply-To: <CAMe9rOpJjaro_qK6kghGNuSHDaP_MjVaZMbok2kbuBD48VmvXg@mail.gmail.com>
I am baffled by this discussion.
>> On Mar 9, 2020, at 5:09 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
>>
>> On Mon, Mar 9, 2020 at 4:59 PM Andy Lutomirski <luto@amacapital.net> wrote:
>
>>>> .
>> This could presumably have been fixed by having libpcre or sljit
>> disable IBT before calling into JIT code or by running the JIT code in
>> another thread. In the other direction, a non-CET libpcre build could
>> build IBT-capable JITted code and enable JIT (by syscall if we allow
>> that or by creating a thread?) when calling it. And IBT has this
>
> This is not how thread in user space works.
void create_cet_thread(void (*func)(), unsigned int cet_flags);
I could implement this using clone() if the kernel provides the requisite support. Sure, creating threads behind libc’s back like this is perilous, but it can be done.
>
>> fancy legacy bitmap to allow non-instrumented code to run with IBT on,
>> although SHSTK doesn't have hardware support for a similar feature.
>
> All these changes are called CET enabing.
What does that mean? If program A loads library B, and library B very carefully loads CET-mismatched code, program A may be blissfully unaware.
>
>> So, sure, the glibc-linked ELF ecosystem needs some degree of CET
>> coordination, but it is absolutely not the case that a process MUST
>> have all CET or no CET. Let's please support the complicated cases in
>> the kernel and the ABI too. If glibc wants to make it annoying to do
>> complicated things, so be it. People work behind glibc's back all the
>> time.
>
> CET is no different from NX in this regard.
NX is in the page tables, and CET, mostly, is not. Also, we seriously flubbed READ_IMPLIES_EXEC and made it affect far more mappings than ever should have been affected.
If a legacy program (non-NX-aware) loads a newer library, and the library opens a device node and mmaps it PROT_READ, it gets RX. This is not a good design. In fact, it’s actively problematic.
Let us please not take Linux’s NX legacy support as an example of good design.
next prev parent reply other threads:[~2020-03-10 1:21 UTC|newest]
Thread overview: 107+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-05 18:19 [RFC PATCH v9 00/27] Control-flow Enforcement: Shadow Stack Yu-cheng Yu
2020-02-05 18:19 ` [RFC PATCH v9 01/27] Documentation/x86: Add CET description Yu-cheng Yu
2020-02-06 0:16 ` Randy Dunlap
[not found] ` <af5ee976-3b57-4afe-6304-fcab8de45c77-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2020-02-06 20:17 ` Yu-cheng Yu
2020-02-25 20:02 ` Kees Cook
2020-02-28 15:55 ` Yu-cheng Yu
2020-02-26 17:57 ` Dave Hansen
2020-03-09 17:00 ` Yu-cheng Yu
2020-03-09 17:21 ` Dave Hansen
2020-03-09 19:27 ` Yu-cheng Yu
2020-03-09 19:35 ` Dave Hansen
2020-03-09 19:50 ` H.J. Lu
2020-03-09 20:16 ` Andy Lutomirski
2020-03-09 20:54 ` H.J. Lu
2020-03-09 20:59 ` Dave Hansen
2020-03-09 21:12 ` H.J. Lu
2020-03-09 22:02 ` Andy Lutomirski
2020-03-09 22:19 ` Dave Hansen
2020-03-09 23:11 ` H.J. Lu
2020-03-09 23:20 ` Dave Hansen
2020-03-09 23:51 ` H.J. Lu
2020-03-09 23:59 ` Andy Lutomirski
2020-03-10 0:08 ` H.J. Lu
2020-03-10 1:21 ` Andy Lutomirski [this message]
2020-03-10 2:13 ` H.J. Lu
2020-02-05 18:19 ` [RFC PATCH v9 03/27] x86/fpu/xstate: Introduce CET MSR XSAVES supervisor states Yu-cheng Yu
2020-02-25 20:04 ` Kees Cook
2020-02-05 18:19 ` [RFC PATCH v9 04/27] x86/cet: Add control-protection fault handler Yu-cheng Yu
2020-02-25 20:06 ` Kees Cook
2020-02-26 17:10 ` Dave Hansen
2020-03-05 20:44 ` Yu-cheng Yu
2020-02-05 18:19 ` [RFC PATCH v9 06/27] mm: Introduce VM_SHSTK for Shadow Stack memory Yu-cheng Yu
2020-02-25 20:07 ` Kees Cook
2020-02-26 18:07 ` Dave Hansen
2020-02-05 18:19 ` [RFC PATCH v9 07/27] Add guard pages around a Shadow Stack Yu-cheng Yu
2020-02-25 20:11 ` Kees Cook
2020-02-26 18:17 ` Dave Hansen
2020-02-05 18:19 ` [RFC PATCH v9 08/27] x86/mm: Change _PAGE_DIRTY to _PAGE_DIRTY_HW Yu-cheng Yu
2020-02-25 20:12 ` Kees Cook
2020-02-26 18:20 ` Dave Hansen
2020-02-05 18:19 ` [RFC PATCH v9 10/27] x86/mm: Update pte_modify, pmd_modify, and _PAGE_CHG_MASK for _PAGE_DIRTY_SW Yu-cheng Yu
2020-02-26 22:02 ` Dave Hansen
2020-02-05 18:19 ` [RFC PATCH v9 11/27] drm/i915/gvt: Change _PAGE_DIRTY to _PAGE_DIRTY_BITS Yu-cheng Yu
2020-02-25 20:13 ` Kees Cook
2020-02-26 22:04 ` Dave Hansen
2020-04-03 15:42 ` Yu-cheng Yu
2020-02-05 18:19 ` [RFC PATCH v9 13/27] x86/mm: Shadow Stack page fault error checking Yu-cheng Yu
2020-02-25 20:16 ` Kees Cook
2020-02-26 22:47 ` Dave Hansen
2020-02-05 18:19 ` [RFC PATCH v9 14/27] mm: Handle Shadow Stack page fault Yu-cheng Yu
2020-02-25 20:20 ` Kees Cook
2020-03-05 18:30 ` Yu-cheng Yu
2020-02-27 0:08 ` Dave Hansen
2020-04-07 18:14 ` Yu-cheng Yu
2020-04-07 22:21 ` Dave Hansen
2020-04-08 18:18 ` Yu-cheng Yu
2020-02-05 18:19 ` [RFC PATCH v9 15/27] mm: Handle THP/HugeTLB " Yu-cheng Yu
2020-02-25 20:59 ` Kees Cook
2020-03-13 22:00 ` Yu-cheng Yu
2020-02-05 18:19 ` [RFC PATCH v9 16/27] mm: Update can_follow_write_pte() for Shadow Stack Yu-cheng Yu
2020-02-27 0:34 ` Dave Hansen
2020-02-05 18:19 ` [RFC PATCH v9 17/27] x86/cet/shstk: User-mode Shadow Stack support Yu-cheng Yu
2020-02-25 21:07 ` Kees Cook
2020-02-27 0:55 ` Dave Hansen
2020-02-05 18:19 ` [RFC PATCH v9 18/27] x86/cet/shstk: Introduce WRUSS instruction Yu-cheng Yu
2020-02-25 21:10 ` Kees Cook
2020-03-05 18:39 ` Yu-cheng Yu
2020-02-05 18:19 ` [RFC PATCH v9 19/27] x86/cet/shstk: Handle signals for Shadow Stack Yu-cheng Yu
2020-02-25 21:17 ` Kees Cook
2020-02-05 18:19 ` [RFC PATCH v9 20/27] ELF: UAPI and Kconfig additions for ELF program properties Yu-cheng Yu
2020-02-05 18:19 ` [RFC PATCH v9 22/27] ELF: Add ELF program property parsing support Yu-cheng Yu
2020-02-25 21:20 ` Kees Cook
2020-02-05 18:19 ` [RFC PATCH v9 23/27] ELF: Introduce arch_setup_elf_property() Yu-cheng Yu
2020-02-05 18:19 ` [RFC PATCH v9 24/27] x86/cet/shstk: ELF header parsing for Shadow Stack Yu-cheng Yu
2020-02-25 21:22 ` Kees Cook
2020-02-05 18:19 ` [RFC PATCH v9 25/27] x86/cet/shstk: Handle thread " Yu-cheng Yu
2020-02-25 21:29 ` Kees Cook
2020-03-25 21:51 ` Yu-cheng Yu
2020-02-05 18:19 ` [RFC PATCH v9 26/27] mm/mmap: Add Shadow Stack pages to memory accounting Yu-cheng Yu
[not found] ` <20200205181935.3712-1-yu-cheng.yu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2020-02-05 18:19 ` [RFC PATCH v9 02/27] x86/cpufeatures: Add CET CPU feature flags for Control-flow Enforcement Technology (CET) Yu-cheng Yu
2020-02-25 20:02 ` Kees Cook
2020-02-05 18:19 ` [RFC PATCH v9 05/27] x86/cet/shstk: Add Kconfig option for user-mode Shadow Stack protection Yu-cheng Yu
2020-02-25 20:07 ` Kees Cook
2020-02-26 17:03 ` Dave Hansen
2020-02-26 19:57 ` Pavel Machek
2020-03-05 20:38 ` Yu-cheng Yu
2020-02-26 18:05 ` Dave Hansen
2020-02-27 1:02 ` H.J. Lu
2020-02-27 1:16 ` Dave Hansen
2020-02-27 2:11 ` H.J. Lu
2020-02-27 3:57 ` Andy Lutomirski
2020-02-27 18:03 ` Dave Hansen
2020-03-06 18:37 ` Yu-cheng Yu
2020-03-06 19:02 ` Dave Hansen
2020-03-06 21:16 ` Yu-cheng Yu
2020-02-05 18:19 ` [RFC PATCH v9 09/27] x86/mm: Introduce _PAGE_DIRTY_SW Yu-cheng Yu
2020-02-25 20:12 ` Kees Cook
2020-02-26 21:35 ` Dave Hansen
2020-04-01 19:08 ` Yu-cheng Yu
2020-04-01 19:22 ` Dave Hansen
2020-02-05 18:19 ` [RFC PATCH v9 12/27] x86/mm: Modify ptep_set_wrprotect and pmdp_set_wrprotect for _PAGE_DIRTY_SW Yu-cheng Yu
2020-02-25 20:14 ` Kees Cook
2020-02-26 22:20 ` Dave Hansen
2020-02-05 18:19 ` [RFC PATCH v9 21/27] binfmt_elf: Define GNU_PROPERTY_X86_FEATURE_1_AND Yu-cheng Yu
2020-02-25 21:18 ` Kees Cook
2020-02-05 18:19 ` [RFC PATCH v9 27/27] x86/cet/shstk: Add arch_prctl functions for Shadow Stack Yu-cheng Yu
2020-02-25 21:31 ` [RFC PATCH v9 00/27] Control-flow Enforcement: " Kees Cook
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