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KAISER: Kernel Address Isolation

Browse source 
This patch introduces our implementation of KAISER (Kernel Address Isolation to
have Side-channels Efficiently Removed), a kernel isolation technique to close
hardware side channels on kernel address information.

More information about the patch can be found on:

        https://github.com/IAIK/KAISER

From: Richard Fellner <richard.fellner@student.tugraz.at>
From: Daniel Gruss <daniel.gruss@iaik.tugraz.at>
Subject: [RFC, PATCH] x86_64: KAISER - do not map kernel in user mode
Date: Thu, 4 May 2017 14:26:50 +0200
Link: http://marc.info/?l=linux-kernel&m=149390087310405&w=2
Kaiser-4.10-SHA1: c4b1831d44c6144d3762ccc72f0c4e71a0c713e5

To: <linux-kernel@vger.kernel.org>
To: <kernel-hardening@lists.openwall.com>
Cc: <clementine.maurice@iaik.tugraz.at>
Cc: <moritz.lipp@iaik.tugraz.at>
Cc: Michael Schwarz <michael.schwarz@iaik.tugraz.at>
Cc: Richard Fellner <richard.fellner@student.tugraz.at>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: <kirill.shutemov@linux.intel.com>
Cc: <anders.fogh@gdata-adan.de>

After several recent works [1,2,3] KASLR on x86_64 was basically
considered dead by many researchers. We have been working on an
efficient but effective fix for this problem and found that not mapping
the kernel space when running in user mode is the solution to this
problem [4] (the corresponding paper [5] will be presented at ESSoS17).

With this RFC patch we allow anybody to configure their kernel with the
flag CONFIG_KAISER to add our defense mechanism.

If there are any questions we would love to answer them.
We also appreciate any comments!

Cheers,
Daniel (+ the KAISER team from Graz University of Technology)

[1] http://www.ieee-security.org/TC/SP2013/papers/4977a191.pdf
[2] https://www.blackhat.com/docs/us-16/materials/us-16-Fogh-Using-Undocumented-CPU-Behaviour-To-See-Into-Kernel-Mode-And-Break-KASLR-In-The-Process.pdf
[3] https://www.blackhat.com/docs/us-16/materials/us-16-Jang-Breaking-Kernel-Address-Space-Layout-Randomization-KASLR-With-Intel-TSX.pdf
[4] https://github.com/IAIK/KAISER
[5] https://gruss.cc/files/kaiser.pdf

[patch based also on
https://raw.githubusercontent.com/IAIK/KAISER/master/KAISER/0001-KAISER-Kernel-Address-Isolation.patch]

Signed-off-by: Richard Fellner <richard.fellner@student.tugraz.at>
Signed-off-by: Moritz Lipp <moritz.lipp@iaik.tugraz.at>
Signed-off-by: Daniel Gruss <daniel.gruss@iaik.tugraz.at>
Signed-off-by: Michael Schwarz <michael.schwarz@iaik.tugraz.at>
Acked-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Richard Fellner 2017-05-04 14:26:50 +02:00 committed by Greg Kroah-Hartman
parent b5fd58e997
commit 13be4483bb
22 changed files with 449 additions and 16 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

17
arch/x86/entry/entry_64.S
View file

@ -36,6 +36,7 @@
#include <asm/smap.h>
#include <asm/pgtable_types.h>
#include <asm/export.h>
#include <asm/kaiser.h>
#include <linux/err.h>
/* Avoid __ASSEMBLER__'ifying <linux/audit.h> just for this. */
@ -146,6 +147,7 @@ ENTRY(entry_SYSCALL_64)
* it is too small to ever cause noticeable irq latency.
*/
SWAPGS_UNSAFE_STACK
SWITCH_KERNEL_CR3_NO_STACK
/*
* A hypervisor implementation might want to use a label
* after the swapgs, so that it can do the swapgs
@ -228,6 +230,7 @@ entry_SYSCALL_64_fastpath:
movq RIP(%rsp), %rcx
movq EFLAGS(%rsp), %r11
RESTORE_C_REGS_EXCEPT_RCX_R11
SWITCH_USER_CR3
movq RSP(%rsp), %rsp
USERGS_SYSRET64
@ -323,10 +326,12 @@ return_from_SYSCALL_64:
syscall_return_via_sysret:
/* rcx and r11 are already restored (see code above) */
RESTORE_C_REGS_EXCEPT_RCX_R11
SWITCH_USER_CR3
movq RSP(%rsp), %rsp
USERGS_SYSRET64
opportunistic_sysret_failed:
SWITCH_USER_CR3
SWAPGS
jmp restore_c_regs_and_iret
END(entry_SYSCALL_64)
@ -424,6 +429,7 @@ ENTRY(ret_from_fork)
movq %rsp, %rdi
call syscall_return_slowpath /* returns with IRQs disabled */
TRACE_IRQS_ON /* user mode is traced as IRQS on */
SWITCH_USER_CR3
SWAPGS
jmp restore_regs_and_iret
@ -478,6 +484,7 @@ END(irq_entries_start)
* tracking that we're in kernel mode.
*/
SWAPGS
SWITCH_KERNEL_CR3
/*
* We need to tell lockdep that IRQs are off. We can't do this until
@ -535,6 +542,7 @@ GLOBAL(retint_user)
mov %rsp,%rdi
call prepare_exit_to_usermode
TRACE_IRQS_IRETQ
SWITCH_USER_CR3
SWAPGS
jmp restore_regs_and_iret
@ -612,6 +620,7 @@ native_irq_return_ldt:
pushq %rdi /* Stash user RDI */
SWAPGS
SWITCH_KERNEL_CR3
movq PER_CPU_VAR(espfix_waddr), %rdi
movq %rax, (0*8)(%rdi) /* user RAX */
movq (1*8)(%rsp), %rax /* user RIP */
@ -638,6 +647,7 @@ native_irq_return_ldt:
* still points to an RO alias of the ESPFIX stack.
*/
orq PER_CPU_VAR(espfix_stack), %rax
SWITCH_USER_CR3
SWAPGS
movq %rax, %rsp
@ -1034,6 +1044,7 @@ ENTRY(paranoid_entry)
testl %edx, %edx
js 1f /* negative -> in kernel */
SWAPGS
SWITCH_KERNEL_CR3
xorl %ebx, %ebx
1: ret
END(paranoid_entry)
@ -1056,6 +1067,7 @@ ENTRY(paranoid_exit)
testl %ebx, %ebx /* swapgs needed? */
jnz paranoid_exit_no_swapgs
TRACE_IRQS_IRETQ
SWITCH_USER_CR3_NO_STACK
SWAPGS_UNSAFE_STACK
jmp paranoid_exit_restore
paranoid_exit_no_swapgs:
@ -1084,6 +1096,7 @@ ENTRY(error_entry)
* from user mode due to an IRET fault.
*/
SWAPGS
SWITCH_KERNEL_CR3
.Lerror_entry_from_usermode_after_swapgs:
/*
@ -1135,6 +1148,7 @@ ENTRY(error_entry)
* Switch to kernel gsbase:
*/
SWAPGS
SWITCH_KERNEL_CR3
/*
* Pretend that the exception came from user mode: set up pt_regs
@ -1235,6 +1249,7 @@ ENTRY(nmi)
*/
SWAPGS_UNSAFE_STACK
SWITCH_KERNEL_CR3_NO_STACK
cld
movq %rsp, %rdx
movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp
@ -1275,6 +1290,7 @@ ENTRY(nmi)
* work, because we don't want to enable interrupts. Fortunately,
* do_nmi doesn't modify pt_regs.
*/
SWITCH_USER_CR3
SWAPGS
jmp restore_c_regs_and_iret
@ -1486,6 +1502,7 @@ end_repeat_nmi:
testl %ebx, %ebx /* swapgs needed? */
jnz nmi_restore
nmi_swapgs:
SWITCH_USER_CR3_NO_STACK
SWAPGS_UNSAFE_STACK
nmi_restore:
RESTORE_EXTRA_REGS

7
arch/x86/entry/entry_64_compat.S
View file

@ -13,6 +13,7 @@
#include <asm/irqflags.h>
#include <asm/asm.h>
#include <asm/smap.h>
#include <asm/kaiser.h>
#include <linux/linkage.h>
#include <linux/err.h>
@ -48,6 +49,7 @@
ENTRY(entry_SYSENTER_compat)
/* Interrupts are off on entry. */
SWAPGS_UNSAFE_STACK
SWITCH_KERNEL_CR3_NO_STACK
movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp
/*
@ -184,6 +186,7 @@ ENDPROC(entry_SYSENTER_compat)
ENTRY(entry_SYSCALL_compat)
/* Interrupts are off on entry. */
SWAPGS_UNSAFE_STACK
SWITCH_KERNEL_CR3_NO_STACK
/* Stash user ESP and switch to the kernel stack. */
movl %esp, %r8d
@ -259,6 +262,7 @@ sysret32_from_system_call:
xorq %r8, %r8
xorq %r9, %r9
xorq %r10, %r10
SWITCH_USER_CR3
movq RSP-ORIG_RAX(%rsp), %rsp
swapgs
sysretl
@ -297,7 +301,7 @@ ENTRY(entry_INT80_compat)
PARAVIRT_ADJUST_EXCEPTION_FRAME
ASM_CLAC /* Do this early to minimize exposure */
SWAPGS
SWITCH_KERNEL_CR3_NO_STACK
/*
* User tracing code (ptrace or signal handlers) might assume that
* the saved RAX contains a 32-bit number when we're invoking a 32-bit
@ -338,6 +342,7 @@ ENTRY(entry_INT80_compat)
/* Go back to user mode. */
TRACE_IRQS_ON
SWITCH_USER_CR3_NO_STACK
SWAPGS
jmp restore_regs_and_iret
END(entry_INT80_compat)

2
arch/x86/include/asm/hw_irq.h
View file

@ -178,7 +178,7 @@ extern char irq_entries_start[];
#define VECTOR_RETRIGGERED ((void *)~0UL)
typedef struct irq_desc* vector_irq_t[NR_VECTORS];
DECLARE_PER_CPU(vector_irq_t, vector_irq);
DECLARE_PER_CPU_USER_MAPPED(vector_irq_t, vector_irq);
#endif /* !ASSEMBLY_ */

113
arch/x86/include/asm/kaiser.h Normal file
View file

@ -0,0 +1,113 @@
#ifndef _ASM_X86_KAISER_H
#define _ASM_X86_KAISER_H
/* This file includes the definitions for the KAISER feature.
* KAISER is a counter measure against x86_64 side channel attacks on the kernel virtual memory.
* It has a shodow-pgd for every process. the shadow-pgd has a minimalistic kernel-set mapped,
* but includes the whole user memory. Within a kernel context switch, or when an interrupt is handled,
* the pgd is switched to the normal one. When the system switches to user mode, the shadow pgd is enabled.
* By this, the virtual memory chaches are freed, and the user may not attack the whole kernel memory.
*
* A minimalistic kernel mapping holds the parts needed to be mapped in user mode, as the entry/exit functions
* of the user space, or the stacks.
*/
#ifdef __ASSEMBLY__
#ifdef CONFIG_KAISER
.macro _SWITCH_TO_KERNEL_CR3 reg
movq %cr3, \reg
andq $(~0x1000), \reg
movq \reg, %cr3
.endm
.macro _SWITCH_TO_USER_CR3 reg
movq %cr3, \reg
orq $(0x1000), \reg
movq \reg, %cr3
.endm
.macro SWITCH_KERNEL_CR3
pushq %rax
_SWITCH_TO_KERNEL_CR3 %rax
popq %rax
.endm
.macro SWITCH_USER_CR3
pushq %rax
_SWITCH_TO_USER_CR3 %rax
popq %rax
.endm
.macro SWITCH_KERNEL_CR3_NO_STACK
movq %rax, PER_CPU_VAR(unsafe_stack_register_backup)
_SWITCH_TO_KERNEL_CR3 %rax
movq PER_CPU_VAR(unsafe_stack_register_backup), %rax
.endm
.macro SWITCH_USER_CR3_NO_STACK
movq %rax, PER_CPU_VAR(unsafe_stack_register_backup)
_SWITCH_TO_USER_CR3 %rax
movq PER_CPU_VAR(unsafe_stack_register_backup), %rax
.endm
#else /* CONFIG_KAISER */
.macro SWITCH_KERNEL_CR3 reg
.endm
.macro SWITCH_USER_CR3 reg
.endm
.macro SWITCH_USER_CR3_NO_STACK
.endm
.macro SWITCH_KERNEL_CR3_NO_STACK
.endm
#endif /* CONFIG_KAISER */
#else /* __ASSEMBLY__ */
#ifdef CONFIG_KAISER
// Upon kernel/user mode switch, it may happen that
// the address space has to be switched before the registers have been stored.
// To change the address space, another register is needed.
// A register therefore has to be stored/restored.
//
DECLARE_PER_CPU_USER_MAPPED(unsigned long, unsafe_stack_register_backup);
#endif /* CONFIG_KAISER */
/**
* shadowmem_add_mapping - map a virtual memory part to the shadow mapping
* @addr: the start address of the range
* @size: the size of the range
* @flags: The mapping flags of the pages
*
* the mapping is done on a global scope, so no bigger synchronization has to be done.
* the pages have to be manually unmapped again when they are not needed any longer.
*/
extern void kaiser_add_mapping(unsigned long addr, unsigned long size, unsigned long flags);
/**
* shadowmem_remove_mapping - unmap a virtual memory part of the shadow mapping
* @addr: the start address of the range
* @size: the size of the range
*/
extern void kaiser_remove_mapping(unsigned long start, unsigned long size);
/**
* shadowmem_initialize_mapping - Initalize the shadow mapping
*
* most parts of the shadow mapping can be mapped upon boot time.
* only the thread stacks have to be mapped on runtime.
* the mapped regions are not unmapped at all.
*/
extern void kaiser_init(void);
#endif
#endif /* _ASM_X86_KAISER_H */

4
arch/x86/include/asm/pgtable.h
View file

@ -904,6 +904,10 @@ static inline void pmdp_set_wrprotect(struct mm_struct *mm,
static inline void clone_pgd_range(pgd_t *dst, pgd_t *src, int count)
{
memcpy(dst, src, count * sizeof(pgd_t));
#ifdef CONFIG_KAISER
// clone the shadow pgd part as well
memcpy(native_get_shadow_pgd(dst), native_get_shadow_pgd(src), count * sizeof(pgd_t));
#endif
}
#define PTE_SHIFT ilog2(PTRS_PER_PTE)

21
arch/x86/include/asm/pgtable_64.h
View file

@ -106,9 +106,30 @@ static inline void native_pud_clear(pud_t *pud)
native_set_pud(pud, native_make_pud(0));
}
#ifdef CONFIG_KAISER
static inline pgd_t * native_get_shadow_pgd(pgd_t *pgdp) {
return (pgd_t *)(void*)((unsigned long)(void*)pgdp | (unsigned long)PAGE_SIZE);
}
static inline pgd_t * native_get_normal_pgd(pgd_t *pgdp) {
return (pgd_t *)(void*)((unsigned long)(void*)pgdp & ~(unsigned long)PAGE_SIZE);
}
#endif /* CONFIG_KAISER */
static inline void native_set_pgd(pgd_t *pgdp, pgd_t pgd)
{
#ifdef CONFIG_KAISER
// We know that a pgd is page aligned.
// Therefore the lower indices have to be mapped to user space.
// These pages are mapped to the shadow mapping.
if ((((unsigned long)pgdp) % PAGE_SIZE) < (PAGE_SIZE / 2)) {
native_get_shadow_pgd(pgdp)->pgd = pgd.pgd;
}
pgdp->pgd = pgd.pgd & ~_PAGE_USER;
#else /* CONFIG_KAISER */
*pgdp = pgd;
#endif
}
static inline void native_pgd_clear(pgd_t *pgd)

12
arch/x86/include/asm/pgtable_types.h
View file

@ -45,7 +45,11 @@
#define _PAGE_ACCESSED (_AT(pteval_t, 1) << _PAGE_BIT_ACCESSED)
#define _PAGE_DIRTY (_AT(pteval_t, 1) << _PAGE_BIT_DIRTY)
#define _PAGE_PSE (_AT(pteval_t, 1) << _PAGE_BIT_PSE)
#define _PAGE_GLOBAL (_AT(pteval_t, 1) << _PAGE_BIT_GLOBAL)
#ifdef CONFIG_KAISER
#define _PAGE_GLOBAL (_AT(pteval_t, 0))
#else
#define _PAGE_GLOBAL (_AT(pteval_t, 1) << _PAGE_BIT_GLOBAL)
#endif
#define _PAGE_SOFTW1 (_AT(pteval_t, 1) << _PAGE_BIT_SOFTW1)
#define _PAGE_SOFTW2 (_AT(pteval_t, 1) << _PAGE_BIT_SOFTW2)
#define _PAGE_PAT (_AT(pteval_t, 1) << _PAGE_BIT_PAT)
@ -119,7 +123,11 @@
#define _PAGE_DEVMAP (_AT(pteval_t, 0))
#endif
#define _PAGE_PROTNONE (_AT(pteval_t, 1) << _PAGE_BIT_PROTNONE)
#ifdef CONFIG_KAISER
#define _PAGE_PROTNONE (_AT(pteval_t, 0))
#else
#define _PAGE_PROTNONE (_AT(pteval_t, 1) << _PAGE_BIT_PROTNONE)
#endif
#define _PAGE_TABLE (_PAGE_PRESENT | _PAGE_RW | _PAGE_USER | \
_PAGE_ACCESSED | _PAGE_DIRTY)

7
arch/x86/include/asm/processor.h
View file

@ -308,7 +308,7 @@ struct tss_struct {
} ____cacheline_aligned;
DECLARE_PER_CPU_SHARED_ALIGNED(struct tss_struct, cpu_tss);
DECLARE_PER_CPU_SHARED_ALIGNED_USER_MAPPED(struct tss_struct, cpu_tss);
#ifdef CONFIG_X86_32
DECLARE_PER_CPU(unsigned long, cpu_current_top_of_stack);
@ -335,6 +335,11 @@ union irq_stack_union {
char gs_base[40];
unsigned long stack_canary;
};
struct {
char irq_stack_pointer[64];
char unused[IRQ_STACK_SIZE - 64];
};
};
DECLARE_PER_CPU_FIRST(union irq_stack_union, irq_stack_union) __visible;

4
arch/x86/kernel/cpu/common.c
View file

@ -93,7 +93,7 @@ static const struct cpu_dev default_cpu = {
static const struct cpu_dev *this_cpu = &default_cpu;
DEFINE_PER_CPU_PAGE_ALIGNED(struct gdt_page, gdt_page) = { .gdt = {
DEFINE_PER_CPU_PAGE_ALIGNED_USER_MAPPED(struct gdt_page, gdt_page) = { .gdt = {
#ifdef CONFIG_X86_64
/*
* We need valid kernel segments for data and code in long mode too
@ -1365,7 +1365,7 @@ static const unsigned int exception_stack_sizes[N_EXCEPTION_STACKS] = {
[DEBUG_STACK - 1] = DEBUG_STKSZ
};
static DEFINE_PER_CPU_PAGE_ALIGNED(char, exception_stacks
DEFINE_PER_CPU_PAGE_ALIGNED_USER_MAPPED(char, exception_stacks
[(N_EXCEPTION_STACKS - 1) * EXCEPTION_STKSZ + DEBUG_STKSZ]);
/* May not be marked __init: used by software suspend */

6
arch/x86/kernel/espfix_64.c
View file

@ -41,6 +41,7 @@
#include <asm/pgalloc.h>
#include <asm/setup.h>
#include <asm/espfix.h>
#include <asm/kaiser.h>
/*
* Note: we only need 6*8 = 48 bytes for the espfix stack, but round
@ -126,6 +127,11 @@ void __init init_espfix_bsp(void)
/* Install the espfix pud into the kernel page directory */
pgd_p = &init_level4_pgt[pgd_index(ESPFIX_BASE_ADDR)];
pgd_populate(&init_mm, pgd_p, (pud_t *)espfix_pud_page);
#ifdef CONFIG_KAISER
// add the esp stack pud to the shadow mapping here.
// This can be done directly, because the fixup stack has its own pud
set_pgd(native_get_shadow_pgd(pgd_p), __pgd(_PAGE_TABLE | __pa((pud_t *)espfix_pud_page)));
#endif
/* Randomize the locations */
init_espfix_random();

16
arch/x86/kernel/head_64.S
View file

@ -405,6 +405,14 @@ GLOBAL(early_recursion_flag)
.balign PAGE_SIZE; \
GLOBAL(name)
#ifdef CONFIG_KAISER
#define NEXT_PGD_PAGE(name) \
.balign 2 * PAGE_SIZE; \
GLOBAL(name)
#else
#define NEXT_PGD_PAGE(name) NEXT_PAGE(name)
#endif
/* Automate the creation of 1 to 1 mapping pmd entries */
#define PMDS(START, PERM, COUNT) \
i = 0 ; \
@ -414,7 +422,7 @@ GLOBAL(name)
.endr
__INITDATA
NEXT_PAGE(early_level4_pgt)
NEXT_PGD_PAGE(early_level4_pgt)
.fill 511,8,0
.quad level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE
@ -424,10 +432,10 @@ NEXT_PAGE(early_dynamic_pgts)
.data
#ifndef CONFIG_XEN
NEXT_PAGE(init_level4_pgt)
.fill 512,8,0
NEXT_PGD_PAGE(init_level4_pgt)
.fill 2*512,8,0
#else
NEXT_PAGE(init_level4_pgt)
NEXT_PGD_PAGE(init_level4_pgt)
.quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
.org init_level4_pgt + L4_PAGE_OFFSET*8, 0
.quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE

2
arch/x86/kernel/irqinit.c
View file

@ -51,7 +51,7 @@ static struct irqaction irq2 = {
.flags = IRQF_NO_THREAD,
};
DEFINE_PER_CPU(vector_irq_t, vector_irq) = {
DEFINE_PER_CPU_USER_MAPPED(vector_irq_t, vector_irq) = {
[0 ... NR_VECTORS - 1] = VECTOR_UNUSED,
};

2
arch/x86/kernel/process.c
View file

@ -41,7 +41,7 @@
* section. Since TSS's are completely CPU-local, we want them
* on exact cacheline boundaries, to eliminate cacheline ping-pong.
*/
__visible DEFINE_PER_CPU_SHARED_ALIGNED(struct tss_struct, cpu_tss) = {
__visible DEFINE_PER_CPU_SHARED_ALIGNED_USER_MAPPED(struct tss_struct, cpu_tss) = {
.x86_tss = {
.sp0 = TOP_OF_INIT_STACK,
#ifdef CONFIG_X86_32

2
arch/x86/mm/Makefile
View file

@ -38,4 +38,4 @@ obj-$(CONFIG_NUMA_EMU) += numa_emulation.o
obj-$(CONFIG_X86_INTEL_MPX) += mpx.o
obj-$(CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS) += pkeys.o
obj-$(CONFIG_RANDOMIZE_MEMORY) += kaslr.o
obj-$(CONFIG_KAISER) += kaiser.o

160
arch/x86/mm/kaiser.c Normal file
View file

@ -0,0 +1,160 @@
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/bug.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/mm.h>
#include <linux/uaccess.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
#include <asm/desc.h>
#ifdef CONFIG_KAISER
__visible DEFINE_PER_CPU_USER_MAPPED(unsigned long, unsafe_stack_register_backup);
/**
* Get the real ppn from a address in kernel mapping.
* @param address The virtual adrress
* @return the physical address
*/
static inline unsigned long get_pa_from_mapping (unsigned long address)
{
pgd_t *pgd;
pud_t *pud;
pmd_t *pmd;
pte_t *pte;
pgd = pgd_offset_k(address);
BUG_ON(pgd_none(*pgd) || pgd_large(*pgd));
pud = pud_offset(pgd, address);
BUG_ON(pud_none(*pud));
if (pud_large(*pud)) {
return (pud_pfn(*pud) << PAGE_SHIFT) | (address & ~PUD_PAGE_MASK);
}
pmd = pmd_offset(pud, address);
BUG_ON(pmd_none(*pmd));
if (pmd_large(*pmd)) {
return (pmd_pfn(*pmd) << PAGE_SHIFT) | (address & ~PMD_PAGE_MASK);
}
pte = pte_offset_kernel(pmd, address);
BUG_ON(pte_none(*pte));
return (pte_pfn(*pte) << PAGE_SHIFT) | (address & ~PAGE_MASK);
}
void _kaiser_copy (unsigned long start_addr, unsigned long size,
unsigned long flags)
{
pgd_t *pgd;
pud_t *pud;
pmd_t *pmd;
pte_t *pte;
unsigned long address;
unsigned long end_addr = start_addr + size;
unsigned long target_address;
for (address = PAGE_ALIGN(start_addr - (PAGE_SIZE - 1));
address < PAGE_ALIGN(end_addr); address += PAGE_SIZE) {
target_address = get_pa_from_mapping(address);
pgd = native_get_shadow_pgd(pgd_offset_k(address));
BUG_ON(pgd_none(*pgd) && "All shadow pgds should be mapped at this time\n");
BUG_ON(pgd_large(*pgd));
pud = pud_offset(pgd, address);
if (pud_none(*pud)) {
set_pud(pud, __pud(_PAGE_TABLE | __pa(pmd_alloc_one(0, address))));
}
BUG_ON(pud_large(*pud));
pmd = pmd_offset(pud, address);
if (pmd_none(*pmd)) {
set_pmd(pmd, __pmd(_PAGE_TABLE | __pa(pte_alloc_one_kernel(0, address))));
}
BUG_ON(pmd_large(*pmd));
pte = pte_offset_kernel(pmd, address);
if (pte_none(*pte)) {
set_pte(pte, __pte(flags | target_address));
} else {
BUG_ON(__pa(pte_page(*pte)) != target_address);
}
}
}
// at first, add a pmd for every pgd entry in the shadowmem-kernel-part of the kernel mapping
static inline void __init _kaiser_init(void)
{
pgd_t *pgd;
int i = 0;
pgd = native_get_shadow_pgd(pgd_offset_k((unsigned long )0));
for (i = PTRS_PER_PGD / 2; i < PTRS_PER_PGD; i++) {
set_pgd(pgd + i, __pgd(_PAGE_TABLE |__pa(pud_alloc_one(0, 0))));
}
}
extern char __per_cpu_user_mapped_start[], __per_cpu_user_mapped_end[];
spinlock_t shadow_table_lock;
void __init kaiser_init(void)
{
int cpu;
spin_lock_init(&shadow_table_lock);
spin_lock(&shadow_table_lock);
_kaiser_init();
for_each_possible_cpu(cpu) {
// map the per cpu user variables
_kaiser_copy(
(unsigned long) (__per_cpu_user_mapped_start + per_cpu_offset(cpu)),
(unsigned long) __per_cpu_user_mapped_end - (unsigned long) __per_cpu_user_mapped_start,
__PAGE_KERNEL);
}
// map the entry/exit text section, which is responsible to switch between user- and kernel mode
_kaiser_copy(
(unsigned long) __entry_text_start,
(unsigned long) __entry_text_end - (unsigned long) __entry_text_start,
__PAGE_KERNEL_RX);
// the fixed map address of the idt_table
_kaiser_copy(
(unsigned long) idt_descr.address,
sizeof(gate_desc) * NR_VECTORS,
__PAGE_KERNEL_RO);
spin_unlock(&shadow_table_lock);
}
// add a mapping to the shadow-mapping, and synchronize the mappings
void kaiser_add_mapping(unsigned long addr, unsigned long size, unsigned long flags)
{
spin_lock(&shadow_table_lock);
_kaiser_copy(addr, size, flags);
spin_unlock(&shadow_table_lock);
}
extern void unmap_pud_range(pgd_t *pgd, unsigned long start, unsigned long end);
void kaiser_remove_mapping(unsigned long start, unsigned long size)
{
pgd_t *pgd = native_get_shadow_pgd(pgd_offset_k(start));
spin_lock(&shadow_table_lock);
do {
unmap_pud_range(pgd, start, start + size);
} while (pgd++ != native_get_shadow_pgd(pgd_offset_k(start + size)));
spin_unlock(&shadow_table_lock);
}
#endif /* CONFIG_KAISER */

2
arch/x86/mm/pageattr.c
View file

@ -823,7 +823,7 @@ static void unmap_pmd_range(pud_t *pud, unsigned long start, unsigned long end)
pud_clear(pud);
}
static void unmap_pud_range(pgd_t *pgd, unsigned long start, unsigned long end)
void unmap_pud_range(pgd_t *pgd, unsigned long start, unsigned long end)
{
pud_t *pud = pud_offset(pgd, start);

26
arch/x86/mm/pgtable.c
View file

@ -346,12 +346,38 @@ static inline void _pgd_free(pgd_t *pgd)
#else
static inline pgd_t *_pgd_alloc(void)
{
#ifdef CONFIG_KAISER
// Instead of one PML4, we aquire two PML4s and, thus, an 8kb-aligned memory
// block. Therefore, we have to allocate at least 3 pages. However, the
// __get_free_pages returns us 4 pages. Hence, we store the base pointer at
// the beginning of the page of our 8kb-aligned memory block in order to
// correctly free it afterwars.
unsigned long pages = __get_free_pages(PGALLOC_GFP, get_order(4*PAGE_SIZE));
if(native_get_normal_pgd((pgd_t*) pages) == (pgd_t*) pages)
{
*((unsigned long*)(pages + 2 * PAGE_SIZE)) = pages;
return (pgd_t *) pages;
}
else
{
*((unsigned long*)(pages + 3 * PAGE_SIZE)) = pages;
return (pgd_t *) (pages + PAGE_SIZE);
}
#else
return (pgd_t *)__get_free_page(PGALLOC_GFP);
#endif
}
static inline void _pgd_free(pgd_t *pgd)
{
#ifdef CONFIG_KAISER
unsigned long pages = *((unsigned long*) ((char*) pgd + 2 * PAGE_SIZE));
free_pages(pages, get_order(4*PAGE_SIZE));
#else
free_page((unsigned long)pgd);
#endif
}
#endif /* CONFIG_X86_PAE */

11
include/asm-generic/vmlinux.lds.h
View file

@ -778,7 +778,16 @@
*/
#define PERCPU_INPUT(cacheline) \
VMLINUX_SYMBOL(__per_cpu_start) = .; \
*(.data..percpu..first) \
\
VMLINUX_SYMBOL(__per_cpu_user_mapped_start) = .; \
*(.data..percpu..first) \
. = ALIGN(cacheline); \
*(.data..percpu..user_mapped) \
*(.data..percpu..user_mapped..shared_aligned) \
. = ALIGN(PAGE_SIZE); \
*(.data..percpu..user_mapped..page_aligned) \
VMLINUX_SYMBOL(__per_cpu_user_mapped_end) = .; \
\
. = ALIGN(PAGE_SIZE); \
*(.data..percpu..page_aligned) \
. = ALIGN(cacheline); \

30
include/linux/percpu-defs.h
View file

@ -35,6 +35,12 @@
#endif
#ifdef CONFIG_KAISER
#define USER_MAPPED_SECTION "..user_mapped"
#else
#define USER_MAPPED_SECTION ""
#endif
/*
* Base implementations of per-CPU variable declarations and definitions, where
* the section in which the variable is to be placed is provided by the
@ -115,6 +121,12 @@
#define DEFINE_PER_CPU(type, name) \
DEFINE_PER_CPU_SECTION(type, name, "")
#define DECLARE_PER_CPU_USER_MAPPED(type, name) \
DECLARE_PER_CPU_SECTION(type, name, USER_MAPPED_SECTION)
#define DEFINE_PER_CPU_USER_MAPPED(type, name) \
DEFINE_PER_CPU_SECTION(type, name, USER_MAPPED_SECTION)
/*
* Declaration/definition used for per-CPU variables that must come first in
* the set of variables.
@ -144,6 +156,14 @@
DEFINE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
____cacheline_aligned_in_smp
#define DECLARE_PER_CPU_SHARED_ALIGNED_USER_MAPPED(type, name) \
DECLARE_PER_CPU_SECTION(type, name, USER_MAPPED_SECTION PER_CPU_SHARED_ALIGNED_SECTION) \
____cacheline_aligned_in_smp
#define DEFINE_PER_CPU_SHARED_ALIGNED_USER_MAPPED(type, name) \
DEFINE_PER_CPU_SECTION(type, name, USER_MAPPED_SECTION PER_CPU_SHARED_ALIGNED_SECTION) \
____cacheline_aligned_in_smp
#define DECLARE_PER_CPU_ALIGNED(type, name) \
DECLARE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION) \
____cacheline_aligned
@ -162,6 +182,16 @@
#define DEFINE_PER_CPU_PAGE_ALIGNED(type, name) \
DEFINE_PER_CPU_SECTION(type, name, "..page_aligned") \
__aligned(PAGE_SIZE)
/*
* Declaration/definition used for per-CPU variables that must be page aligned and need to be mapped in user mode.
*/
#define DECLARE_PER_CPU_PAGE_ALIGNED_USER_MAPPED(type, name) \
DECLARE_PER_CPU_SECTION(type, name, USER_MAPPED_SECTION"..page_aligned") \
__aligned(PAGE_SIZE)
#define DEFINE_PER_CPU_PAGE_ALIGNED_USER_MAPPED(type, name) \
DEFINE_PER_CPU_SECTION(type, name, USER_MAPPED_SECTION"..page_aligned") \
__aligned(PAGE_SIZE)
/*
* Declaration/definition used for per-CPU variables that must be read mostly.

6
init/main.c
View file

@ -86,6 +86,9 @@
#include <asm/setup.h>
#include <asm/sections.h>
#include <asm/cacheflush.h>
#ifdef CONFIG_KAISER
#include <asm/kaiser.h>
#endif
static int kernel_init(void *);
@ -473,6 +476,9 @@ static void __init mm_init(void)
pgtable_init();
vmalloc_init();
ioremap_huge_init();
#ifdef CONFIG_KAISER
kaiser_init();
#endif
}
asmlinkage __visible void __init start_kernel(void)

8
kernel/fork.c
View file

@ -211,8 +211,12 @@ static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
#endif
}
extern void kaiser_remove_mapping(unsigned long start_addr, unsigned long size);
static inline void free_thread_stack(struct task_struct *tsk)
{
#ifdef CONFIG_KAISER
kaiser_remove_mapping((unsigned long)tsk->stack, THREAD_SIZE);
#endif
#ifdef CONFIG_VMAP_STACK
if (task_stack_vm_area(tsk)) {
unsigned long flags;
@ -468,6 +472,7 @@ void set_task_stack_end_magic(struct task_struct *tsk)
*stackend = STACK_END_MAGIC; /* for overflow detection */
}
extern void kaiser_add_mapping(unsigned long addr, unsigned long size, unsigned long flags);
static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
{
struct task_struct *tsk;
@ -495,6 +500,9 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
* functions again.
*/
tsk->stack = stack;
#ifdef CONFIG_KAISER
kaiser_add_mapping((unsigned long)tsk->stack, THREAD_SIZE, __PAGE_KERNEL);
#endif
#ifdef CONFIG_VMAP_STACK
tsk->stack_vm_area = stack_vm_area;
#endif

7
security/Kconfig
View file

@ -30,6 +30,13 @@ config SECURITY
model will be used.
If you are unsure how to answer this question, answer N.
config KAISER
bool "Remove the kernel mapping in user mode"
depends on X86_64
depends on !PARAVIRT
help
This enforces a strict kernel and user space isolation in order to close
hardware side channels on kernel address information.
config SECURITYFS
bool "Enable the securityfs filesystem"