From: Yu-cheng Yu <yu-cheng.yu@intel.com>
To: 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>, 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>,
Weijiang Yang <weijiang.yang@intel.com>,
Pengfei Xu <pengfei.xu@intel.com>,
Haitao Huang <haitao.huang@intel.com>
Cc: Yu-cheng Yu <yu-cheng.yu@intel.com>
Subject: [PATCH v23 28/28] mm: Introduce PROT_SHSTK for shadow stack
Date: Tue, 16 Mar 2021 08:10:54 -0700 [thread overview]
Message-ID: <20210316151054.5405-29-yu-cheng.yu@intel.com> (raw)
In-Reply-To: <20210316151054.5405-1-yu-cheng.yu@intel.com>
There are three possible options to create a shadow stack allocation API:
an arch_prctl, a new syscall, or adding PROT_SHSTK to mmap()/mprotect().
Each has its advantages and compromises.
An arch_prctl() is the least intrusive. However, the existing x86
arch_prctl() takes only two parameters. Multiple parameters must be
passed in a memory buffer. There is a proposal to pass more parameters in
registers [1], but no active discussion on that.
A new syscall minimizes compatibility issues and offers an extensible frame
work to other architectures, but this will likely result in some overlap of
mmap()/mprotect().
The introduction of PROT_SHSTK to mmap()/mprotect() takes advantage of
existing APIs. The x86-specific PROT_SHSTK is translated to VM_SHSTK and
a shadow stack mapping is created without reinventing the wheel. There are
potential pitfalls though. The most obvious one would be using this as a
bypass to shadow stack protection. However, the attacker would have to get
to the syscall first.
[1] https://lore.kernel.org/lkml/20200828121624.108243-1-hjl.tools@gmail.com/
Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
arch/x86/include/asm/mman.h | 57 +++++++++++++++++++++++++++++++-
arch/x86/include/uapi/asm/mman.h | 1 +
include/linux/mm.h | 1 +
mm/mmap.c | 8 ++++-
4 files changed, 65 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/mman.h b/arch/x86/include/asm/mman.h
index 629f6c81263a..bd94e30b5d34 100644
--- a/arch/x86/include/asm/mman.h
+++ b/arch/x86/include/asm/mman.h
@@ -20,11 +20,66 @@
((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) (0)
+#endif
+
+static inline unsigned long arch_calc_vm_prot_bits(unsigned long prot,
+ unsigned long pkey)
+{
+ unsigned long vm_prot_bits = pkey_vm_prot_bits(prot, pkey);
+
+ if (!(prot & PROT_WRITE) && (prot & PROT_SHSTK))
+ vm_prot_bits |= VM_SHSTK;
+
+ return vm_prot_bits;
+}
+
+#define arch_calc_vm_prot_bits(prot, pkey) arch_calc_vm_prot_bits(prot, pkey)
+
+#ifdef CONFIG_X86_CET
+static inline bool arch_validate_prot(unsigned long prot, unsigned long addr)
+{
+ unsigned long valid = PROT_READ | PROT_WRITE | PROT_EXEC | PROT_SEM;
+
+ if (prot & ~(valid | PROT_SHSTK))
+ return false;
+
+ if (prot & PROT_SHSTK) {
+ struct vm_area_struct *vma;
+
+ if (!current->thread.cet.shstk_size)
+ return false;
+
+ /*
+ * A shadow stack mapping is indirectly writable by only
+ * the CALL and WRUSS instructions, but not other write
+ * instructions). PROT_SHSTK and PROT_WRITE are mutually
+ * exclusive.
+ */
+ if (prot & PROT_WRITE)
+ return false;
+
+ vma = find_vma(current->mm, addr);
+ if (!vma)
+ return false;
+
+ /*
+ * Shadow stack cannot be backed by a file or shared.
+ */
+ if (vma->vm_file || (vma->vm_flags & VM_SHARED))
+ return false;
+ }
+
+ return true;
+}
+
+#define arch_validate_prot arch_validate_prot
#endif
#endif /* _ASM_X86_MMAN_H */
diff --git a/arch/x86/include/uapi/asm/mman.h b/arch/x86/include/uapi/asm/mman.h
index 3ce1923e6ed9..39bb7db344a6 100644
--- a/arch/x86/include/uapi/asm/mman.h
+++ b/arch/x86/include/uapi/asm/mman.h
@@ -4,6 +4,7 @@
#define MAP_32BIT 0x40 /* only give out 32bit addresses */
+#define PROT_SHSTK 0x10 /* shadow stack pages */
#include <asm-generic/mman.h>
diff --git a/include/linux/mm.h b/include/linux/mm.h
index e178be052419..40c4b0fe7cc4 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -342,6 +342,7 @@ extern unsigned int kobjsize(const void *objp);
#if defined(CONFIG_X86)
# define VM_PAT VM_ARCH_1 /* PAT reserves whole VMA at once (x86) */
+# define VM_ARCH_CLEAR VM_SHSTK
#elif defined(CONFIG_PPC)
# define VM_SAO VM_ARCH_1 /* Strong Access Ordering (powerpc) */
#elif defined(CONFIG_PARISC)
diff --git a/mm/mmap.c b/mm/mmap.c
index 99077171010b..934cb3cbe952 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1481,6 +1481,12 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
struct inode *inode = file_inode(file);
unsigned long flags_mask;
+ /*
+ * Call stack cannot be backed by a file.
+ */
+ if (vm_flags & VM_SHSTK)
+ return -EINVAL;
+
if (!file_mmap_ok(file, inode, pgoff, len))
return -EOVERFLOW;
@@ -1545,7 +1551,7 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
} else {
switch (flags & MAP_TYPE) {
case MAP_SHARED:
- if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
+ if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP|VM_SHSTK))
return -EINVAL;
/*
* Ignore pgoff.
--
2.21.0
next prev parent reply other threads:[~2021-03-16 15:15 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-16 15:10 [PATCH v23 00/28] Control-flow Enforcement: Shadow Stack Yu-cheng Yu
2021-03-16 15:10 ` [PATCH v23 01/28] Documentation/x86: Add CET description Yu-cheng Yu
2021-03-16 15:10 ` [PATCH v23 02/28] x86/cet/shstk: Add Kconfig option for user-mode control-flow protection Yu-cheng Yu
2021-03-16 15:10 ` [PATCH v23 03/28] x86/cpufeatures: Add CET CPU feature flags for Control-flow Enforcement Technology (CET) Yu-cheng Yu
2021-03-16 15:10 ` [PATCH v23 04/28] x86/cpufeatures: Introduce X86_FEATURE_CET and setup functions Yu-cheng Yu
2021-03-16 15:10 ` [PATCH v23 05/28] x86/fpu/xstate: Introduce CET MSR and XSAVES supervisor states Yu-cheng Yu
2021-03-16 15:10 ` [PATCH v23 06/28] x86/cet: Add control-protection fault handler Yu-cheng Yu
2021-03-16 15:10 ` [PATCH v23 07/28] x86/mm: Remove _PAGE_DIRTY from kernel RO pages Yu-cheng Yu
2021-03-22 9:13 ` Kirill A. Shutemov
2021-03-22 14:52 ` Yu, Yu-cheng
2021-03-16 15:10 ` [PATCH v23 08/28] x86/mm: Move pmd_write(), pud_write() up in the file Yu-cheng Yu
2021-03-22 11:28 ` Kirill A. Shutemov
2021-03-16 15:10 ` [PATCH v23 09/28] x86/mm: Introduce _PAGE_COW Yu-cheng Yu
2021-03-22 11:29 ` Kirill A. Shutemov
2021-03-16 15:10 ` [PATCH v23 10/28] drm/i915/gvt: Change _PAGE_DIRTY to _PAGE_DIRTY_BITS Yu-cheng Yu
2021-03-22 11:30 ` Kirill A. Shutemov
2021-03-16 15:10 ` [PATCH v23 11/28] x86/mm: Update pte_modify for _PAGE_COW Yu-cheng Yu
2021-03-22 11:31 ` Kirill A. Shutemov
2021-03-16 15:10 ` [PATCH v23 12/28] x86/mm: Update ptep_set_wrprotect() and pmdp_set_wrprotect() for transition from _PAGE_DIRTY to _PAGE_COW Yu-cheng Yu
2021-03-22 10:15 ` Kirill A. Shutemov
2021-03-22 10:46 ` Peter Zijlstra
2021-03-22 11:38 ` Kirill A. Shutemov
2021-03-16 15:10 ` [PATCH v23 13/28] mm: Introduce VM_SHSTK for shadow stack memory Yu-cheng Yu
2021-03-22 11:33 ` Kirill A. Shutemov
2021-03-16 15:10 ` [PATCH v23 14/28] x86/mm: Shadow Stack page fault error checking Yu-cheng Yu
2021-03-22 10:38 ` Kirill A. Shutemov
2021-03-22 17:27 ` Yu, Yu-cheng
2021-03-16 15:10 ` [PATCH v23 15/28] x86/mm: Update maybe_mkwrite() for shadow stack Yu-cheng Yu
2021-03-17 15:56 ` Borislav Petkov
2021-03-22 10:46 ` Kirill A. Shutemov
2021-03-16 15:10 ` [PATCH v23 16/28] mm: Fixup places that call pte_mkwrite() directly Yu-cheng Yu
2021-03-18 9:47 ` Borislav Petkov
2021-03-18 11:16 ` Borislav Petkov
2021-03-16 15:10 ` [PATCH v23 17/28] mm: Add guard pages around a shadow stack Yu-cheng Yu
2021-03-22 10:55 ` Kirill A. Shutemov
2021-03-16 15:10 ` [PATCH v23 18/28] mm/mmap: Add shadow stack pages to memory accounting Yu-cheng Yu
2021-03-22 10:57 ` Kirill A. Shutemov
2021-03-26 15:46 ` Yu, Yu-cheng
2021-03-29 10:10 ` Kirill A. Shutemov
2021-03-16 15:10 ` [PATCH v23 19/28] mm: Update can_follow_write_pte() for shadow stack Yu-cheng Yu
2021-03-16 15:10 ` [PATCH v23 20/28] mm/mprotect: Exclude shadow stack from preserve_write Yu-cheng Yu
2021-03-16 15:10 ` [PATCH v23 21/28] mm: Re-introduce vm_flags to do_mmap() Yu-cheng Yu
2021-03-18 11:42 ` Borislav Petkov
2021-03-18 15:59 ` Yu, Yu-cheng
2021-03-18 16:13 ` Borislav Petkov
2021-03-16 15:10 ` [PATCH v23 22/28] x86/cet/shstk: User-mode shadow stack support Yu-cheng Yu
2021-03-18 12:32 ` Borislav Petkov
2021-03-18 19:05 ` Yu, Yu-cheng
2021-03-19 9:28 ` Borislav Petkov
2021-03-19 15:15 ` Yu, Yu-cheng
2021-03-16 15:10 ` [PATCH v23 23/28] x86/cet/shstk: Handle signals for shadow stack Yu-cheng Yu
2021-03-19 12:51 ` Borislav Petkov
2021-03-16 15:10 ` [PATCH v23 24/28] ELF: Introduce arch_setup_elf_property() Yu-cheng Yu
2021-03-16 15:10 ` [PATCH v23 25/28] x86/cet/shstk: Handle thread shadow stack Yu-cheng Yu
2021-03-16 15:10 ` [PATCH v23 26/28] x86/cet/shstk: Add arch_prctl functions for " Yu-cheng Yu
2021-03-16 15:10 ` [PATCH v23 27/28] mm: Move arch_calc_vm_prot_bits() to arch/x86/include/asm/mman.h Yu-cheng Yu
2021-03-16 15:10 ` Yu-cheng Yu [this message]
2021-03-22 11:27 ` [PATCH v23 28/28] mm: Introduce PROT_SHSTK for shadow stack Kirill A. Shutemov
2021-03-16 21:15 ` [PATCH v23 00/28] Control-flow Enforcement: Shadow Stack Peter Zijlstra
2021-03-16 21:34 ` Yu, Yu-cheng
2021-03-17 9:18 ` Ingo Molnar
2021-03-17 10:14 ` Peter Zijlstra
2021-03-19 16:24 ` Yu, Yu-cheng
2021-03-19 21:43 ` Yu, Yu-cheng
2021-03-23 20:49 ` Peter Zijlstra
2021-03-23 21:03 ` Yu, Yu-cheng
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