From: Andy Lutomirski <luto@amacapital.net>
To: Jann Horn <jannh@google.com>
Cc: 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>,
kernel list <linux-kernel@vger.kernel.org>,
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>,
bsingharora@gmail.com, Cyrill Gorcunov <gorcunov@gmail.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Florian Weimer <fweimer@redhat.com>,
hjl.tools@gmail.com, Jonathan Corbet <corbet@lwn.net>,
keescook@chromiun.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>,
ravi.v.shankar@intel.com, vedvyas.shanbhogue@intel.com
Subject: Re: [RFC PATCH v2 17/27] x86/cet/shstk: User-mode shadow stack support
Date: Wed, 11 Jul 2018 15:21:58 -0700 [thread overview]
Message-ID: <A034EC34-13E7-4AEF-BB3C-FEF14143B601@amacapital.net> (raw)
In-Reply-To: <CAG48ez1OwQMmhQfHaauo+vneywsQ_ERKr4uVcQebC=GbdqZWtA@mail.gmail.com>
> On Jul 11, 2018, at 2:51 PM, Jann Horn <jannh@google.com> wrote:
>
> On Wed, Jul 11, 2018 at 2:34 PM Andy Lutomirski <luto@amacapital.net> wrote:
>>> On Jul 11, 2018, at 2:10 PM, Jann Horn <jannh@google.com> wrote:
>>>
>>>> On Tue, Jul 10, 2018 at 3:31 PM Yu-cheng Yu <yu-cheng.yu@intel.com> wrote:
>>>>
>>>> This patch adds basic shadow stack enabling/disabling routines.
>>>> A task's shadow stack is allocated from memory with VM_SHSTK
>>>> flag set and read-only protection. The shadow stack is
>>>> allocated to a fixed size.
>>>>
>>>> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
>>> [...]
>>>> diff --git a/arch/x86/kernel/cet.c b/arch/x86/kernel/cet.c
>>>> new file mode 100644
>>>> index 000000000000..96bf69db7da7
>>>> --- /dev/null
>>>> +++ b/arch/x86/kernel/cet.c
>>> [...]
>>>> +static unsigned long shstk_mmap(unsigned long addr, unsigned long len)
>>>> +{
>>>> + struct mm_struct *mm = current->mm;
>>>> + unsigned long populate;
>>>> +
>>>> + down_write(&mm->mmap_sem);
>>>> + addr = do_mmap(NULL, addr, len, PROT_READ,
>>>> + MAP_ANONYMOUS | MAP_PRIVATE, VM_SHSTK,
>>>> + 0, &populate, NULL);
>>>> + up_write(&mm->mmap_sem);
>>>> +
>>>> + if (populate)
>>>> + mm_populate(addr, populate);
>>>> +
>>>> + return addr;
>>>> +}
> [...]
>>> Should the kernel enforce that two shadow stacks must have a guard
>>> page between them so that they can not be directly adjacent, so that
>>> if you have too much recursion, you can't end up corrupting an
>>> adjacent shadow stack?
>>
>> I think the answer is a qualified “no”. I would like to instead enforce a general guard page on all mmaps that don’t use MAP_FORCE. We *might* need to exempt any mmap with an address hint for compatibility.
>
> I like this idea a lot.
>
>> My commercial software has been manually adding guard pages on every single mmap done by tcmalloc for years, and it has caught a couple bugs and costs essentially nothing.
>>
>> Hmm. Linux should maybe add something like Windows’ “reserved” virtual memory. It’s basically a way to ask for a VA range that explicitly contains nothing and can be subsequently be turned into something useful with the equivalent of MAP_FORCE.
>
> What's the benefit over creating an anonymous PROT_NONE region? That
> the kernel won't have to scan through the corresponding PTEs when
> tearing down the mapping?
Make it more obvious what’s happening and avoid accounting issues? What I’ve actually used is MAP_NORESERVE | PROT_NONE, but I think this still counts against the VA rlimit. But maybe that’s actually the desired behavior.
next prev parent reply other threads:[~2018-07-11 22:22 UTC|newest]
Thread overview: 123+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-10 22:26 [RFC PATCH v2 00/27] Control Flow Enforcement (CET) Yu-cheng Yu
2018-07-10 22:26 ` [RFC PATCH v2 01/27] x86/cpufeatures: Add CPUIDs for Control-flow Enforcement Technology (CET) Yu-cheng Yu
2018-07-10 22:26 ` [RFC PATCH v2 02/27] x86/fpu/xstate: Change some names to separate XSAVES system and user states Yu-cheng Yu
2018-07-10 22:26 ` [RFC PATCH v2 03/27] x86/fpu/xstate: Enable XSAVES system states Yu-cheng Yu
2018-07-10 22:26 ` [RFC PATCH v2 04/27] x86/fpu/xstate: Add XSAVES system states for shadow stack Yu-cheng Yu
2018-07-10 22:26 ` [RFC PATCH v2 05/27] Documentation/x86: Add CET description Yu-cheng Yu
2018-07-11 8:27 ` Pavel Machek
2018-07-11 15:25 ` Yu-cheng Yu
2018-07-11 9:57 ` Florian Weimer
2018-07-11 13:47 ` H.J. Lu
2018-07-11 14:53 ` Yu-cheng Yu
2018-07-10 22:26 ` [RFC PATCH v2 06/27] x86/cet: Control protection exception handler Yu-cheng Yu
2018-07-10 22:26 ` [RFC PATCH v2 07/27] x86/cet/shstk: Add Kconfig option for user-mode shadow stack Yu-cheng Yu
2018-07-10 22:26 ` [RFC PATCH v2 08/27] mm: Introduce VM_SHSTK for shadow stack memory Yu-cheng Yu
2018-07-11 8:34 ` Peter Zijlstra
2018-07-11 16:15 ` Yu-cheng Yu
2018-07-10 22:26 ` [RFC PATCH v2 09/27] x86/mm: Change _PAGE_DIRTY to _PAGE_DIRTY_HW Yu-cheng Yu
2018-07-10 22:26 ` [RFC PATCH v2 10/27] x86/mm: Introduce _PAGE_DIRTY_SW Yu-cheng Yu
2018-07-11 8:45 ` Peter Zijlstra
2018-07-11 9:21 ` Peter Zijlstra
2018-07-10 22:26 ` [RFC PATCH v2 11/27] x86/mm: Modify ptep_set_wrprotect and pmdp_set_wrprotect for _PAGE_DIRTY_SW Yu-cheng Yu
2018-07-10 22:44 ` Dave Hansen
2018-07-10 23:23 ` Nadav Amit
2018-07-10 23:52 ` Dave Hansen
2018-07-11 8:48 ` Peter Zijlstra
2018-07-10 22:26 ` [RFC PATCH v2 12/27] x86/mm: Shadow stack page fault error checking Yu-cheng Yu
2018-07-10 22:52 ` Dave Hansen
2018-07-11 17:28 ` Yu-cheng Yu
2018-07-10 23:24 ` Dave Hansen
2018-07-10 22:26 ` [RFC PATCH v2 13/27] mm: Handle shadow stack page fault Yu-cheng Yu
2018-07-10 23:06 ` Dave Hansen
2018-07-11 9:06 ` Peter Zijlstra
2018-08-14 21:28 ` Yu-cheng Yu
2018-07-10 22:26 ` [RFC PATCH v2 14/27] mm: Handle THP/HugeTLB " Yu-cheng Yu
2018-07-10 23:08 ` Dave Hansen
2018-07-11 9:10 ` Peter Zijlstra
2018-07-11 16:11 ` Yu-cheng Yu
2018-07-20 14:20 ` Dave Hansen
2018-07-20 14:58 ` Yu-cheng Yu
2018-07-10 22:26 ` [RFC PATCH v2 15/27] mm/mprotect: Prevent mprotect from changing shadow stack Yu-cheng Yu
2018-07-10 23:10 ` Dave Hansen
2018-07-11 9:12 ` Peter Zijlstra
2018-07-11 16:07 ` Yu-cheng Yu
2018-07-11 16:22 ` Dave Hansen
2018-07-10 22:26 ` [RFC PATCH v2 16/27] mm: Modify can_follow_write_pte/pmd for " Yu-cheng Yu
2018-07-10 23:37 ` Dave Hansen
2018-07-11 17:05 ` Yu-cheng Yu
2018-07-13 18:26 ` Dave Hansen
2018-07-17 23:03 ` Yu-cheng Yu
2018-07-17 23:11 ` Dave Hansen
2018-07-17 23:15 ` Dave Hansen
2018-07-18 20:14 ` Yu-cheng Yu
2018-07-18 21:45 ` Dave Hansen
2018-07-18 23:10 ` Yu-cheng Yu
2018-07-19 0:06 ` Dave Hansen
2018-07-19 17:06 ` Yu-cheng Yu
2018-07-19 19:31 ` Dave Hansen
2018-07-11 9:29 ` Peter Zijlstra
2018-07-17 23:00 ` Yu-cheng Yu
2018-07-10 22:26 ` [RFC PATCH v2 17/27] x86/cet/shstk: User-mode shadow stack support Yu-cheng Yu
2018-07-10 23:40 ` Dave Hansen
2018-07-11 9:34 ` Peter Zijlstra
2018-07-11 15:45 ` Yu-cheng Yu
2018-07-11 9:36 ` Peter Zijlstra
2018-07-11 21:10 ` Jann Horn
2018-07-11 21:34 ` Andy Lutomirski
2018-07-11 21:51 ` Jann Horn
2018-07-11 22:21 ` Andy Lutomirski [this message]
2018-07-13 18:03 ` Yu-cheng Yu
2018-07-10 22:26 ` [RFC PATCH v2 18/27] x86/cet/shstk: Introduce WRUSS instruction Yu-cheng Yu
2018-07-10 23:48 ` Dave Hansen
2018-07-12 22:59 ` Yu-cheng Yu
2018-07-12 23:49 ` Dave Hansen
2018-07-13 1:50 ` Dave Hansen
2018-07-13 2:21 ` Andy Lutomirski
2018-07-13 4:16 ` Dave Hansen
2018-07-13 4:18 ` Dave Hansen
2018-07-13 17:39 ` Yu-cheng Yu
2018-07-13 5:55 ` Andy Lutomirski
2018-07-11 9:44 ` Peter Zijlstra
2018-07-11 15:06 ` Yu-cheng Yu
2018-07-11 15:30 ` Peter Zijlstra
2018-07-11 9:45 ` Peter Zijlstra
2018-07-11 14:58 ` Yu-cheng Yu
2018-07-11 15:27 ` Peter Zijlstra
2018-07-11 15:41 ` Yu-cheng Yu
2018-07-13 12:12 ` Dave Hansen
2018-07-13 17:37 ` Yu-cheng Yu
2018-07-10 22:26 ` [RFC PATCH v2 19/27] x86/cet/shstk: Signal handling for shadow stack Yu-cheng Yu
2018-07-10 22:26 ` [RFC PATCH v2 20/27] x86/cet/shstk: ELF header parsing of CET Yu-cheng Yu
2018-07-11 11:12 ` Florian Weimer
2018-07-11 19:37 ` Jann Horn
2018-07-11 20:53 ` Yu-cheng Yu
2018-07-10 22:26 ` [RFC PATCH v2 21/27] x86/cet/ibt: Add Kconfig option for user-mode Indirect Branch Tracking Yu-cheng Yu
2018-07-10 22:26 ` [RFC PATCH v2 22/27] x86/cet/ibt: User-mode indirect branch tracking support Yu-cheng Yu
2018-07-11 0:11 ` Dave Hansen
2018-07-11 22:10 ` Yu-cheng Yu
2018-07-11 22:40 ` Dave Hansen
2018-07-11 23:00 ` Yu-cheng Yu
2018-07-11 23:16 ` Dave Hansen
2018-07-13 17:56 ` Yu-cheng Yu
2018-07-13 18:05 ` Dave Hansen
2018-07-11 21:07 ` Jann Horn
2018-07-10 22:26 ` [RFC PATCH v2 23/27] mm/mmap: Add IBT bitmap size to address space limit check Yu-cheng Yu
2018-07-10 23:57 ` Dave Hansen
2018-07-11 16:56 ` Yu-cheng Yu
2018-07-10 22:26 ` [RFC PATCH v2 24/27] x86: Insert endbr32/endbr64 to vDSO Yu-cheng Yu
2018-07-10 22:26 ` [RFC PATCH v2 25/27] x86/cet: Add PTRACE interface for CET Yu-cheng Yu
2018-07-11 10:20 ` Ingo Molnar
2018-07-11 15:40 ` Yu-cheng Yu
2018-07-12 14:03 ` Ingo Molnar
2018-07-12 22:37 ` Yu-cheng Yu
2018-07-12 23:08 ` Thomas Gleixner
2018-07-13 16:07 ` Yu-cheng Yu
2018-07-13 6:28 ` Pavel Machek
2018-07-13 13:33 ` Ingo Molnar
2018-07-14 6:27 ` Pavel Machek
2018-07-10 22:26 ` [RFC PATCH v2 26/27] x86/cet/shstk: Handle thread shadow stack Yu-cheng Yu
2018-07-10 22:26 ` [RFC PATCH v2 27/27] x86/cet: Add arch_prctl functions for CET Yu-cheng Yu
2018-07-11 12:19 ` Florian Weimer
2018-07-11 21:02 ` Yu-cheng Yu
2018-07-11 19:45 ` Jann Horn
2018-07-11 20:55 ` Yu-cheng Yu
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