From: Yu-cheng Yu <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: [PATCH v11 25/25] x86/cet/shstk: Add arch_prctl functions for shadow stack
Date: Fri, 11 Sep 2020 15:59:56 -0700 [thread overview]
Message-ID: <a1efc4330a3beff10671949eddbba96f8cde96da.camel@intel.com> (raw)
In-Reply-To: <b3379d26-d8a7-deb7-59f1-c994bb297dcb@intel.com>
On Wed, 2020-09-09 at 16:29 -0700, Dave Hansen wrote:
> On 9/9/20 4:25 PM, Yu, Yu-cheng wrote:
> > On 9/9/2020 4:11 PM, Dave Hansen wrote:
> > > On 9/9/20 4:07 PM, Yu, Yu-cheng wrote:
> > > > What if a writable mapping is passed to madvise(MADV_SHSTK)? Should
> > > > that be rejected?
> > >
> > > It doesn't matter to me. Even if it's readable, it _stops_ being even
> > > directly readable after it's a shadow stack, right? I don't think
> > > writes are special in any way. If anything, we *want* it to be writable
> > > because that indicates that it can be written to, and we will want to
> > > write to it soon.
> > >
> > But in a PROT_WRITE mapping, all the pte's have _PAGE_BIT_RW set. To
> > change them to shadow stack, we need to clear that bit from the pte's.
> > That will be like mprotect_fixup()/change_protection_range().
>
> The page table hardware bits don't matter. The user-visible protection
> effects matter.
>
> For instance, we have PROT_EXEC, which *CLEARS* a hardware NX PTE bit.
> The PROT_ permissions are independent of the hardware.
>
> I don't think the interface should be influenced at *all* by what whacko
> PTE bit combinations we have to set to get the behavior.
Here are the changes if we take the mprotect(PROT_SHSTK) approach.
Any comments/suggestions?
---
arch/x86/include/uapi/asm/mman.h | 26 +++++++++++++++++++++++++-
mm/mprotect.c | 11 +++++++++++
2 files changed, 36 insertions(+), 1 deletion(-)
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
+#define shstk_vm_prot_bits(prot) ( \
+ (static_cpu_has(X86_FEATURE_SHSTK) && (prot & PROT_SHSTK)) ? \
+ VM_SHSTK : 0)
+
+#define arch_calc_vm_prot_bits(prot, key) \
+ (pkey_vm_prot_bits(prot, key) | shstk_vm_prot_bits(prot))
+
#include <asm-generic/mman.h>
+static inline bool arch_validate_prot(unsigned long prot, unsigned long addr)
+{
+ unsigned long supported = PROT_READ | PROT_EXEC | PROT_SEM;
+
+ if (static_cpu_has(X86_FEATURE_SHSTK) && (prot & PROT_SHSTK))
+ supported |= PROT_SHSTK;
+ else
+ supported |= PROT_WRITE;
+
+ return (prot & ~supported) == 0;
+}
+#define arch_validate_prot arch_validate_prot
+
#endif /* _ASM_X86_MMAN_H */
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.
+ */
+ if (prot & PROT_SHSTK) {
+ if (vma->vm_file) {
+ error = -EINVAL;
+ goto out;
+ }
+ }
+
if (start > vma->vm_start)
prev = vma;
--
next prev parent reply other threads:[~2020-09-11 23:00 UTC|newest]
Thread overview: 89+ 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
[not found] ` <46dffdfd-92f8-0f05-6164-945f217b0958@intel.com>
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 [this message]
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
[not found] ` <bf2ab309-f8c4-83da-1c0a-5684e5bc5c82@intel.com>
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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