Commit 54007f81 authored by Yu-cheng Yu's avatar Yu-cheng Yu Committed by Rick Edgecombe
Browse files

mm: Introduce VM_SHADOW_STACK for shadow stack memory 



New hardware extensions implement support for shadow stack memory, such
as x86 Control-flow Enforcement Technology (CET). Add a new VM flag to
identify these areas, for example, to be used to properly indicate shadow
stack PTEs to the hardware.

Shadow stack VMA creation will be tightly controlled and limited to
anonymous memory to make the implementation simpler and since that is all
that is required. The solution will rely on pte_mkwrite() to create the
shadow stack PTEs, so it will not be required for vm_get_page_prot() to
learn how to create shadow stack memory. For this reason document that
VM_SHADOW_STACK should not be mixed with VM_SHARED.

Co-developed-by: default avatarRick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: default avatarYu-cheng Yu <yu-cheng.yu@intel.com>
Signed-off-by: default avatarRick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Reviewed-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: default avatarMark Brown <broonie@kernel.org>
Acked-by: default avatarMike Rapoport (IBM) <rppt@kernel.org>
Acked-by: default avatarDavid Hildenbrand <david@redhat.com>
Tested-by: default avatarMark Brown <broonie@kernel.org>
Tested-by: default avatarPengfei Xu <pengfei.xu@intel.com>
Tested-by: default avatarJohn Allen <john.allen@amd.com>
Tested-by: default avatarKees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/all/20230613001108.3040476-15-rick.p.edgecombe%40intel.com
parent f788b717

Documentation/filesystems/proc.rst

+1 −0
Original line number Diff line number Diff line
@@ -566,6 +566,7 @@ 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

fs/proc/task_mmu.c

+3 −0
Original line number Diff line number Diff line
@@ -709,6 +709,9 @@ 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;

include/linux/mm.h

+8 −0
Original line number Diff line number Diff line
@@ -319,11 +319,13 @@ 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
@@ -339,6 +341,12 @@ 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 /* Should not be set with VM_SHARED */

#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)