[PATCH v3 14/37] mm: Introduce VM_SHADOW_STACK for shadow stack memory
From: Rick Edgecombe <rick.p.edgecombe@intel.com>
Date: 2022-11-04 22:41:48
Also in:
linux-arch, linux-doc, linux-mm, lkml
Subsystem:
documentation, filesystems (vfs and infrastructure), memory management - core, memory mapping, proc filesystem, the rest · Maintainers:
Jonathan Corbet, Alexander Viro, Christian Brauner, Andrew Morton, David Hildenbrand, Liam R. Howlett, Lorenzo Stoakes, Linus Torvalds
From: Yu-cheng Yu <redacted> The x86 Control-flow Enforcement Technology (CET) feature includes a new type of memory called shadow stack. This shadow stack memory has some unusual properties, which requires some core mm changes to function properly. A shadow stack PTE must be read-only and have _PAGE_DIRTY set. However, read-only and Dirty PTEs also exist for copy-on-write (COW) pages. These two cases are handled differently for page faults. Introduce VM_SHADOW_STACK to track shadow stack VMAs. Tested-by: Pengfei Xu <redacted> Tested-by: John Allen <john.allen@amd.com> Signed-off-by: Yu-cheng Yu <redacted> Reviewed-by: Kirill A. Shutemov <redacted> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com> Cc: Kees Cook <redacted> --- v3: - Drop arch specific change in arch_vma_name(). The memory can show as anonymous (Kirill) - Change CONFIG_ARCH_HAS_SHADOW_STACK to CONFIG_X86_USER_SHADOW_STACK in show_smap_vma_flags() (Boris) Documentation/filesystems/proc.rst | 1 + fs/proc/task_mmu.c | 3 +++ include/linux/mm.h | 8 ++++++++ 3 files changed, 12 insertions(+)
diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
index 898c99eae8e4..05506dfa0480 100644
--- a/Documentation/filesystems/proc.rst
+++ b/Documentation/filesystems/proc.rst@@ -560,6 +560,7 @@ encoded manner. The codes are the following: mt arm64 MTE allocation tags are enabled um userfaultfd missing tracking uw userfaultfd wr-protect tracking + ss shadow stack page == ======================================= Note that there is no guarantee that every flag and associated mnemonic will
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 8a74cdcc9af0..7dee7afbb01b 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c@@ -703,6 +703,9 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma) #ifdef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR [ilog2(VM_UFFD_MINOR)] = "ui", #endif /* CONFIG_HAVE_ARCH_USERFAULTFD_MINOR */ +#ifdef CONFIG_X86_USER_SHADOW_STACK + [ilog2(VM_SHADOW_STACK)] = "ss", +#endif }; size_t i;
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 5314ad0a342d..42c4e4bc972d 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h@@ -314,11 +314,13 @@ extern unsigned int kobjsize(const void *objp); #define VM_HIGH_ARCH_BIT_2 34 /* bit only usable on 64-bit architectures */ #define VM_HIGH_ARCH_BIT_3 35 /* bit only usable on 64-bit architectures */ #define VM_HIGH_ARCH_BIT_4 36 /* bit only usable on 64-bit architectures */ +#define VM_HIGH_ARCH_BIT_5 37 /* bit only usable on 64-bit architectures */ #define VM_HIGH_ARCH_0 BIT(VM_HIGH_ARCH_BIT_0) #define VM_HIGH_ARCH_1 BIT(VM_HIGH_ARCH_BIT_1) #define VM_HIGH_ARCH_2 BIT(VM_HIGH_ARCH_BIT_2) #define VM_HIGH_ARCH_3 BIT(VM_HIGH_ARCH_BIT_3) #define VM_HIGH_ARCH_4 BIT(VM_HIGH_ARCH_BIT_4) +#define VM_HIGH_ARCH_5 BIT(VM_HIGH_ARCH_BIT_5) #endif /* CONFIG_ARCH_USES_HIGH_VMA_FLAGS */ #ifdef CONFIG_ARCH_HAS_PKEYS
@@ -334,6 +336,12 @@ extern unsigned int kobjsize(const void *objp); #endif #endif /* CONFIG_ARCH_HAS_PKEYS */ +#ifdef CONFIG_X86_USER_SHADOW_STACK +# define VM_SHADOW_STACK VM_HIGH_ARCH_5 +#else +# define VM_SHADOW_STACK VM_NONE +#endif + #if defined(CONFIG_X86) # define VM_PAT VM_ARCH_1 /* PAT reserves whole VMA at once (x86) */ #elif defined(CONFIG_PPC)
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2.17.1