From: "Yu, Yu-cheng" <yu-cheng.yu@intel.com>
To: Dave Hansen <dave.hansen@intel.com>, Andy Lutomirski <luto@kernel.org>
Cc: Dave Martin <Dave.Martin@arm.com>,
"H.J. Lu" <hjl.tools@gmail.com>,
Florian Weimer <fweimer@redhat.com>, X86 ML <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>,
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>,
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>,
Weijiang Yang <weijiang.yang@intel.com>
Subject: Re: [NEEDS-REVIEW] Re: [PATCH v11 25/25] x86/cet/shstk: Add arch_prctl functions for shadow stack
Date: Mon, 14 Sep 2020 17:12:54 -0700 [thread overview]
Message-ID: <bf2ab309-f8c4-83da-1c0a-5684e5bc5c82@intel.com> (raw)
In-Reply-To: <41aa5e8f-ad88-2934-6d10-6a78fcbe019b@intel.com>
On 9/14/2020 7:50 AM, Dave Hansen wrote:
> On 9/11/20 3:59 PM, Yu-cheng Yu wrote:
> ...
>> Here are the changes if we take the mprotect(PROT_SHSTK) approach.
>> Any comments/suggestions?
>
> I still don't like it. :)
>
> I'll also be much happier when there's a proper changelog to accompany
> this which also spells out the alternatives any why they suck so much.
>
>> diff --git a/arch/x86/include/uapi/asm/mman.h b/arch/x86/include/uapi/asm/mman.h
>> index d4a8d0424bfb..024f006fcfe8 100644
>> --- a/arch/x86/include/uapi/asm/mman.h
>> +++ b/arch/x86/include/uapi/asm/mman.h
>> @@ -4,6 +4,8 @@
>>
>> #define MAP_32BIT 0x40 /* only give out 32bit addresses */
>>
>> +#define PROT_SHSTK 0x10 /* shadow stack pages */
>> +
>> #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
>> /*
>> * Take the 4 protection key bits out of the vma->vm_flags
>> @@ -19,13 +21,35 @@
>> ((vm_flags) & VM_PKEY_BIT2 ? _PAGE_PKEY_BIT2 : 0) | \
>> ((vm_flags) & VM_PKEY_BIT3 ? _PAGE_PKEY_BIT3 : 0))
>>
>> -#define arch_calc_vm_prot_bits(prot, key) ( \
>> +#define pkey_vm_prot_bits(prot, key) ( \
>> ((key) & 0x1 ? VM_PKEY_BIT0 : 0) | \
>> ((key) & 0x2 ? VM_PKEY_BIT1 : 0) | \
>> ((key) & 0x4 ? VM_PKEY_BIT2 : 0) | \
>> ((key) & 0x8 ? VM_PKEY_BIT3 : 0))
>> +#else
>> +#define pkey_vm_prot_bits(prot, key)
>> #endif
>
> My inner compiler doesn't think this will compile:
>
> ( | shstk_vm_prot_bits(prot))
>
>
>> +#define shstk_vm_prot_bits(prot) ( \
>> + (static_cpu_has(X86_FEATURE_SHSTK) && (prot & PROT_SHSTK)) ? \
>> + VM_SHSTK : 0)
>
> Why do you need to filter PROT_SHSTK twice. Won't the prot passed in
> here be filtered by arch_validate_prot()?
X86_FEATURE_SHSTK is already checked by arch_validate_prot() and may be
skipped. PROT_SHSTK needs to be tested and translated to VM_SHSTK here.
>
>> +#define arch_calc_vm_prot_bits(prot, key) \
>> + (pkey_vm_prot_bits(prot, key) | shstk_vm_prot_bits(prot))
>> +
>
> IMNHO, this is eminently more readable if you do:
>
> #define arch_calc_vm_prot_bits(prot, key) \
> (shstk_vm_prot_bits(prot)) \
> pkey_vm_prot_bits(prot, key))
>
> BTW, can these be static inlines? I forget if I had a good reason for
> making them #defines.
Probably, at compile time, ((key) & 0x1 ? (VM_PKEY_BIT0 : 0) cannot be
optimized out, unless there is a #define? Since we are adding the
shadow stack stuff, why don't we make it static inline?
Also do we want to check if the cpu has PKEY?
[...]
>> diff --git a/mm/mprotect.c b/mm/mprotect.c
>> index a8edbcb3af99..520bd8caa005 100644
>> --- a/mm/mprotect.c
>> +++ b/mm/mprotect.c
>> @@ -571,6 +571,17 @@ static int do_mprotect_pkey(unsigned long start, size_t
>> len,
>> goto out;
>> }
>> }
>> +
>> + /*
>> + * Only anonymous mapping is suitable for shadow stack.
>> + */
>
> Why?
When a file mapping is turned into shadow stack, then the logic is
strange. For instance, when a CALL triggers a shadow stack page fault,
do we page in from a file? At least this seems to defeat shadow stack.
next prev parent reply other threads:[~2020-09-15 0:13 UTC|newest]
Thread overview: 91+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-25 0:25 [PATCH v11 00/25] Control-flow Enforcement: Shadow Stack Yu-cheng Yu
2020-08-25 0:25 ` [PATCH v11 01/25] Documentation/x86: Add CET description Yu-cheng Yu
2020-08-25 0:25 ` [PATCH v11 02/25] x86/cpufeatures: Add CET CPU feature flags for Control-flow Enforcement Technology (CET) Yu-cheng Yu
2020-08-25 0:25 ` [PATCH v11 03/25] x86/fpu/xstate: Introduce CET MSR XSAVES supervisor states Yu-cheng Yu
2020-08-25 0:25 ` [PATCH v11 04/25] x86/cet: Add control-protection fault handler Yu-cheng Yu
2020-08-25 0:25 ` [PATCH v11 05/25] x86/cet/shstk: Add Kconfig option for user-mode Shadow Stack Yu-cheng Yu
2020-08-25 0:25 ` [PATCH v11 06/25] x86/mm: Change _PAGE_DIRTY to _PAGE_DIRTY_HW Yu-cheng Yu
2020-08-25 0:25 ` [PATCH v11 07/25] x86/mm: Remove _PAGE_DIRTY_HW from kernel RO pages Yu-cheng Yu
2020-08-25 0:25 ` [PATCH v11 08/25] x86/mm: Introduce _PAGE_COW Yu-cheng Yu
2020-08-25 0:25 ` [PATCH v11 09/25] drm/i915/gvt: Change _PAGE_DIRTY to _PAGE_DIRTY_BITS Yu-cheng Yu
2020-08-25 0:25 ` [PATCH v11 10/25] x86/mm: Update pte_modify for _PAGE_COW Yu-cheng Yu
2020-08-25 0:25 ` [PATCH v11 11/25] x86/mm: Update ptep_set_wrprotect() and pmdp_set_wrprotect() for transition from _PAGE_DIRTY_HW to _PAGE_COW Yu-cheng Yu
2020-08-25 0:25 ` [PATCH v11 12/25] mm: Introduce VM_SHSTK for shadow stack memory Yu-cheng Yu
2020-08-25 0:25 ` [PATCH v11 13/25] x86/mm: Shadow Stack page fault error checking Yu-cheng Yu
2020-08-25 0:25 ` [PATCH v11 14/25] x86/mm: Update maybe_mkwrite() for shadow stack Yu-cheng Yu
2020-08-25 0:25 ` [PATCH v11 15/25] mm: Fixup places that call pte_mkwrite() directly Yu-cheng Yu
2020-08-25 0:25 ` [PATCH v11 16/25] mm: Add guard pages around a shadow stack Yu-cheng Yu
2020-08-25 0:25 ` [PATCH v11 17/25] mm/mmap: Add shadow stack pages to memory accounting Yu-cheng Yu
2020-08-25 0:25 ` [PATCH v11 18/25] mm: Update can_follow_write_pte() for shadow stack Yu-cheng Yu
2020-08-25 0:25 ` [PATCH v11 19/25] mm: Re-introduce do_mmap_pgoff() Yu-cheng Yu
2020-08-25 0:25 ` [PATCH v11 20/25] x86/cet/shstk: User-mode shadow stack support Yu-cheng Yu
2020-08-25 0:25 ` [PATCH v11 21/25] x86/cet/shstk: Handle signals for shadow stack Yu-cheng Yu
2020-08-25 0:25 ` [PATCH v11 22/25] binfmt_elf: Define GNU_PROPERTY_X86_FEATURE_1_AND properties Yu-cheng Yu
2020-08-25 0:25 ` [PATCH v11 23/25] ELF: Introduce arch_setup_elf_property() Yu-cheng Yu
2020-08-25 0:25 ` [PATCH v11 24/25] x86/cet/shstk: Handle thread shadow stack Yu-cheng Yu
2020-08-25 0:25 ` [PATCH v11 25/25] x86/cet/shstk: Add arch_prctl functions for " Yu-cheng Yu
2020-08-25 0:36 ` Andy Lutomirski
2020-08-25 18:43 ` Yu, Yu-cheng
2020-08-25 19:19 ` Dave Hansen
2020-08-25 21:04 ` Yu, Yu-cheng
2020-08-25 23:20 ` Dave Hansen
2020-08-25 23:34 ` Yu, Yu-cheng
2020-08-26 16:46 ` Dave Martin
2020-08-26 16:51 ` Florian Weimer
2020-08-26 17:04 ` Andy Lutomirski
2020-08-26 18:49 ` Yu, Yu-cheng
2020-08-26 19:43 ` H.J. Lu
2020-08-26 19:57 ` Dave Hansen
2020-08-27 13:26 ` H.J. Lu
2020-09-01 10:28 ` Dave Martin
2020-09-01 17:23 ` Yu, Yu-cheng
2020-09-01 17:45 ` Andy Lutomirski
2020-09-01 18:11 ` Dave Hansen
2020-09-02 13:58 ` Dave Martin
2020-09-08 17:50 ` Yu, Yu-cheng
2020-09-08 17:57 ` Dave Hansen
2020-09-08 18:25 ` Yu, Yu-cheng
2020-09-09 22:08 ` Yu, Yu-cheng
2020-09-09 22:59 ` Dave Hansen
2020-09-09 23:07 ` Yu, Yu-cheng
2020-09-09 23:11 ` Dave Hansen
2020-09-09 23:25 ` Yu, Yu-cheng
2020-09-09 23:29 ` Dave Hansen
2020-09-09 23:45 ` Yu, Yu-cheng
2020-09-11 22:59 ` Yu-cheng Yu
2020-09-14 14:50 ` [NEEDS-REVIEW] " Dave Hansen
2020-09-14 18:31 ` Andy Lutomirski
2020-09-14 20:44 ` Yu, Yu-cheng
2020-09-14 21:14 ` Dave Hansen
2020-09-16 13:52 ` Andy Lutomirski
2020-09-16 19:25 ` Yu, Yu-cheng
2021-09-14 1:33 ` [NEEDS-REVIEW] " Edgecombe, Rick P
2021-09-14 9:53 ` Borislav Petkov
2021-09-20 16:48 ` Andy Lutomirski
2021-09-23 23:32 ` Edgecombe, Rick P
2020-09-15 0:12 ` Yu, Yu-cheng [this message]
2020-09-15 19:08 ` Yu-cheng Yu
2020-09-15 19:24 ` Dave Hansen
2020-09-15 20:16 ` Yu, Yu-cheng
2020-08-26 17:08 ` Dave Martin
2020-08-27 13:18 ` Florian Weimer
2020-08-27 13:28 ` H.J. Lu
2020-08-27 13:36 ` Florian Weimer
2020-08-27 14:07 ` H.J. Lu
2020-08-27 14:08 ` H.J. Lu
2020-09-01 17:49 ` Yu, Yu-cheng
2020-09-01 17:50 ` Florian Weimer
2020-09-01 17:58 ` Yu, Yu-cheng
2020-09-01 18:17 ` Florian Weimer
2020-09-01 18:19 ` H.J. Lu
2020-09-01 18:24 ` Yu, Yu-cheng
2020-08-27 18:13 ` Yu, Yu-cheng
2020-08-27 18:56 ` Andy Lutomirski
2020-08-27 19:33 ` Yu, Yu-cheng
2020-08-27 19:37 ` H.J. Lu
2020-08-28 1:35 ` Andy Lutomirski
2020-08-28 1:44 ` H.J. Lu
2020-08-28 6:23 ` Florian Weimer
2020-08-28 11:37 ` H.J. Lu
2020-08-28 17:39 ` Andy Lutomirski
2020-08-28 17:45 ` H.J. Lu
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