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Merge branch 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Browse Source 
Pull x86 pti bits and fixes from Thomas Gleixner:
 "This last update contains:

   - An objtool fix to prevent a segfault with the gold linker by
     changing the invocation order. That's not just for gold, it's a
     general robustness improvement.

   - An improved error message for objtool which spares tearing hairs.

   - Make KASAN fail loudly if there is not enough memory instead of
     oopsing at some random place later

   - RSB fill on context switch to prevent RSB underflow and speculation
     through other units.

   - Make the retpoline/RSB functionality work reliably for both Intel
     and AMD

   - Add retpoline to the module version magic so mismatch can be
     detected

   - A small (non-fix) update for cpufeatures which prevents cpu feature
     clashing for the upcoming extra mitigation bits to ease
     backporting"

* 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  module: Add retpoline tag to VERMAGIC
  x86/cpufeature: Move processor tracing out of scattered features
  objtool: Improve error message for bad file argument
  objtool: Fix seg fault with gold linker
  x86/retpoline: Add LFENCE to the retpoline/RSB filling RSB macros
  x86/retpoline: Fill RSB on context switch for affected CPUs
  x86/kasan: Panic if there is not enough memory to boot
This commit is contained in:
Linus Torvalds 2018-01-17 11:54:56 -08:00
commit 88dc7fca18
10 changed files with 99 additions and 19 deletions
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11
arch/x86/entry/entry_32.S
View File

@ -244,6 +244,17 @@ ENTRY(__switch_to_asm)
movl %ebx, PER_CPU_VAR(stack_canary)+stack_canary_offset
#endif
#ifdef CONFIG_RETPOLINE
/*
* When switching from a shallower to a deeper call stack
* the RSB may either underflow or use entries populated
* with userspace addresses. On CPUs where those concerns
* exist, overwrite the RSB with entries which capture
* speculative execution to prevent attack.
*/
FILL_RETURN_BUFFER %ebx, RSB_CLEAR_LOOPS, X86_FEATURE_RSB_CTXSW
#endif
/* restore callee-saved registers */
popl %esi
popl %edi

11
arch/x86/entry/entry_64.S
View File

@ -491,6 +491,17 @@ ENTRY(__switch_to_asm)
movq %rbx, PER_CPU_VAR(irq_stack_union)+stack_canary_offset
#endif
#ifdef CONFIG_RETPOLINE
/*
* When switching from a shallower to a deeper call stack
* the RSB may either underflow or use entries populated
* with userspace addresses. On CPUs where those concerns
* exist, overwrite the RSB with entries which capture
* speculative execution to prevent attack.
*/
FILL_RETURN_BUFFER %r12, RSB_CLEAR_LOOPS, X86_FEATURE_RSB_CTXSW
#endif
/* restore callee-saved registers */
popq %r15
popq %r14

3
arch/x86/include/asm/cpufeatures.h
View File

@ -206,11 +206,11 @@
#define X86_FEATURE_RETPOLINE ( 7*32+12) /* Generic Retpoline mitigation for Spectre variant 2 */
#define X86_FEATURE_RETPOLINE_AMD ( 7*32+13) /* AMD Retpoline mitigation for Spectre variant 2 */
#define X86_FEATURE_INTEL_PPIN ( 7*32+14) /* Intel Processor Inventory Number */
#define X86_FEATURE_INTEL_PT ( 7*32+15) /* Intel Processor Trace */
#define X86_FEATURE_AVX512_4VNNIW ( 7*32+16) /* AVX-512 Neural Network Instructions */
#define X86_FEATURE_AVX512_4FMAPS ( 7*32+17) /* AVX-512 Multiply Accumulation Single precision */
#define X86_FEATURE_MBA ( 7*32+18) /* Memory Bandwidth Allocation */
#define X86_FEATURE_RSB_CTXSW ( 7*32+19) /* Fill RSB on context switches */
/* Virtualization flags: Linux defined, word 8 */
#define X86_FEATURE_TPR_SHADOW ( 8*32+ 0) /* Intel TPR Shadow */
@ -245,6 +245,7 @@
#define X86_FEATURE_AVX512IFMA ( 9*32+21) /* AVX-512 Integer Fused Multiply-Add instructions */
#define X86_FEATURE_CLFLUSHOPT ( 9*32+23) /* CLFLUSHOPT instruction */
#define X86_FEATURE_CLWB ( 9*32+24) /* CLWB instruction */
#define X86_FEATURE_INTEL_PT ( 9*32+25) /* Intel Processor Trace */
#define X86_FEATURE_AVX512PF ( 9*32+26) /* AVX-512 Prefetch */
#define X86_FEATURE_AVX512ER ( 9*32+27) /* AVX-512 Exponential and Reciprocal */
#define X86_FEATURE_AVX512CD ( 9*32+28) /* AVX-512 Conflict Detection */

6
arch/x86/include/asm/nospec-branch.h
View File

@ -11,7 +11,7 @@
* Fill the CPU return stack buffer.
*
* Each entry in the RSB, if used for a speculative 'ret', contains an
* infinite 'pause; jmp' loop to capture speculative execution.
* infinite 'pause; lfence; jmp' loop to capture speculative execution.
*
* This is required in various cases for retpoline and IBRS-based
* mitigations for the Spectre variant 2 vulnerability. Sometimes to
@ -38,11 +38,13 @@
call 772f; \
773: /* speculation trap */ \
pause; \
lfence; \
jmp 773b; \
772: \
call 774f; \
775: /* speculation trap */ \
pause; \
lfence; \
jmp 775b; \
774: \
dec reg; \
@ -73,6 +75,7 @@
call .Ldo_rop_\@
.Lspec_trap_\@:
pause
lfence
jmp .Lspec_trap_\@
.Ldo_rop_\@:
mov \reg, (%_ASM_SP)
@ -165,6 +168,7 @@
" .align 16\n" \
"901: call 903f;\n" \
"902: pause;\n" \
" lfence;\n" \
" jmp 902b;\n" \
" .align 16\n" \
"903: addl $4, %%esp;\n" \

36
arch/x86/kernel/cpu/bugs.c
View File

@ -23,6 +23,7 @@
#include <asm/alternative.h>
#include <asm/pgtable.h>
#include <asm/set_memory.h>
#include <asm/intel-family.h>
static void __init spectre_v2_select_mitigation(void);
@ -155,6 +156,23 @@ disable:
return SPECTRE_V2_CMD_NONE;
}
/* Check for Skylake-like CPUs (for RSB handling) */
static bool __init is_skylake_era(void)
{
if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
boot_cpu_data.x86 == 6) {
switch (boot_cpu_data.x86_model) {
case INTEL_FAM6_SKYLAKE_MOBILE:
case INTEL_FAM6_SKYLAKE_DESKTOP:
case INTEL_FAM6_SKYLAKE_X:
case INTEL_FAM6_KABYLAKE_MOBILE:
case INTEL_FAM6_KABYLAKE_DESKTOP:
return true;
}
}
return false;
}
static void __init spectre_v2_select_mitigation(void)
{
enum spectre_v2_mitigation_cmd cmd = spectre_v2_parse_cmdline();
@ -213,6 +231,24 @@ retpoline_auto:
spectre_v2_enabled = mode;
pr_info("%s\n", spectre_v2_strings[mode]);
/*
* If neither SMEP or KPTI are available, there is a risk of
* hitting userspace addresses in the RSB after a context switch
* from a shallow call stack to a deeper one. To prevent this fill
* the entire RSB, even when using IBRS.
*
* Skylake era CPUs have a separate issue with *underflow* of the
* RSB, when they will predict 'ret' targets from the generic BTB.
* The proper mitigation for this is IBRS. If IBRS is not supported
* or deactivated in favour of retpolines the RSB fill on context
* switch is required.
*/
if ((!boot_cpu_has(X86_FEATURE_PTI) &&
!boot_cpu_has(X86_FEATURE_SMEP)) || is_skylake_era()) {
setup_force_cpu_cap(X86_FEATURE_RSB_CTXSW);
pr_info("Filling RSB on context switch\n");
}
}
#undef pr_fmt

1
arch/x86/kernel/cpu/scattered.c
View File

@ -21,7 +21,6 @@ struct cpuid_bit {
static const struct cpuid_bit cpuid_bits[] = {
{ X86_FEATURE_APERFMPERF, CPUID_ECX, 0, 0x00000006, 0 },
{ X86_FEATURE_EPB, CPUID_ECX, 3, 0x00000006, 0 },
{ X86_FEATURE_INTEL_PT, CPUID_EBX, 25, 0x00000007, 0 },
{ X86_FEATURE_AVX512_4VNNIW, CPUID_EDX, 2, 0x00000007, 0 },
{ X86_FEATURE_AVX512_4FMAPS, CPUID_EDX, 3, 0x00000007, 0 },
{ X86_FEATURE_CAT_L3, CPUID_EBX, 1, 0x00000010, 0 },

24
arch/x86/mm/kasan_init_64.c
View File

@ -21,10 +21,14 @@ extern struct range pfn_mapped[E820_MAX_ENTRIES];
static p4d_t tmp_p4d_table[PTRS_PER_P4D] __initdata __aligned(PAGE_SIZE);
static __init void *early_alloc(size_t size, int nid)
static __init void *early_alloc(size_t size, int nid, bool panic)
{
return memblock_virt_alloc_try_nid_nopanic(size, size,
__pa(MAX_DMA_ADDRESS), BOOTMEM_ALLOC_ACCESSIBLE, nid);
if (panic)
return memblock_virt_alloc_try_nid(size, size,
__pa(MAX_DMA_ADDRESS), BOOTMEM_ALLOC_ACCESSIBLE, nid);
else
return memblock_virt_alloc_try_nid_nopanic(size, size,
__pa(MAX_DMA_ADDRESS), BOOTMEM_ALLOC_ACCESSIBLE, nid);
}
static void __init kasan_populate_pmd(pmd_t *pmd, unsigned long addr,
@ -38,14 +42,14 @@ static void __init kasan_populate_pmd(pmd_t *pmd, unsigned long addr,
if (boot_cpu_has(X86_FEATURE_PSE) &&
((end - addr) == PMD_SIZE) &&
IS_ALIGNED(addr, PMD_SIZE)) {
p = early_alloc(PMD_SIZE, nid);
p = early_alloc(PMD_SIZE, nid, false);
if (p && pmd_set_huge(pmd, __pa(p), PAGE_KERNEL))
return;
else if (p)
memblock_free(__pa(p), PMD_SIZE);
}
p = early_alloc(PAGE_SIZE, nid);
p = early_alloc(PAGE_SIZE, nid, true);
pmd_populate_kernel(&init_mm, pmd, p);
}
@ -57,7 +61,7 @@ static void __init kasan_populate_pmd(pmd_t *pmd, unsigned long addr,
if (!pte_none(*pte))
continue;
p = early_alloc(PAGE_SIZE, nid);
p = early_alloc(PAGE_SIZE, nid, true);
entry = pfn_pte(PFN_DOWN(__pa(p)), PAGE_KERNEL);
set_pte_at(&init_mm, addr, pte, entry);
} while (pte++, addr += PAGE_SIZE, addr != end);
@ -75,14 +79,14 @@ static void __init kasan_populate_pud(pud_t *pud, unsigned long addr,
if (boot_cpu_has(X86_FEATURE_GBPAGES) &&
((end - addr) == PUD_SIZE) &&
IS_ALIGNED(addr, PUD_SIZE)) {
p = early_alloc(PUD_SIZE, nid);
p = early_alloc(PUD_SIZE, nid, false);
if (p && pud_set_huge(pud, __pa(p), PAGE_KERNEL))
return;
else if (p)
memblock_free(__pa(p), PUD_SIZE);
}
p = early_alloc(PAGE_SIZE, nid);
p = early_alloc(PAGE_SIZE, nid, true);
pud_populate(&init_mm, pud, p);
}
@ -101,7 +105,7 @@ static void __init kasan_populate_p4d(p4d_t *p4d, unsigned long addr,
unsigned long next;
if (p4d_none(*p4d)) {
void *p = early_alloc(PAGE_SIZE, nid);
void *p = early_alloc(PAGE_SIZE, nid, true);
p4d_populate(&init_mm, p4d, p);
}
@ -122,7 +126,7 @@ static void __init kasan_populate_pgd(pgd_t *pgd, unsigned long addr,
unsigned long next;
if (pgd_none(*pgd)) {
p = early_alloc(PAGE_SIZE, nid);
p = early_alloc(PAGE_SIZE, nid, true);
pgd_populate(&init_mm, pgd, p);
}

8
include/linux/vermagic.h
View File

@ -31,11 +31,17 @@
#else
#define MODULE_RANDSTRUCT_PLUGIN
#endif
#ifdef RETPOLINE
#define MODULE_VERMAGIC_RETPOLINE "retpoline "
#else
#define MODULE_VERMAGIC_RETPOLINE ""
#endif
#define VERMAGIC_STRING \
UTS_RELEASE " " \
MODULE_VERMAGIC_SMP MODULE_VERMAGIC_PREEMPT \
MODULE_VERMAGIC_MODULE_UNLOAD MODULE_VERMAGIC_MODVERSIONS \
MODULE_ARCH_VERMAGIC \
MODULE_RANDSTRUCT_PLUGIN
MODULE_RANDSTRUCT_PLUGIN \
MODULE_VERMAGIC_RETPOLINE

14
scripts/Makefile.build
View File

@ -265,12 +265,18 @@ else
objtool_args += $(call cc-ifversion, -lt, 0405, --no-unreachable)
endif
ifdef CONFIG_MODVERSIONS
objtool_o = $(@D)/.tmp_$(@F)
else
objtool_o = $(@)
endif
# 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory
# 'OBJECT_FILES_NON_STANDARD_foo.o := 'y': skip objtool checking for a file
# 'OBJECT_FILES_NON_STANDARD_foo.o := 'n': override directory skip for a file
cmd_objtool = $(if $(patsubst y%,, \
$(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
$(__objtool_obj) $(objtool_args) "$(@)";)
$(__objtool_obj) $(objtool_args) "$(objtool_o)";)
objtool_obj = $(if $(patsubst y%,, \
$(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
$(__objtool_obj))
@ -286,16 +292,16 @@ objtool_dep = $(objtool_obj) \
define rule_cc_o_c
$(call echo-cmd,checksrc) $(cmd_checksrc) \
$(call cmd_and_fixdep,cc_o_c) \
$(cmd_modversions_c) \
$(cmd_checkdoc) \
$(call echo-cmd,objtool) $(cmd_objtool) \
$(cmd_modversions_c) \
$(call echo-cmd,record_mcount) $(cmd_record_mcount)
endef
define rule_as_o_S
$(call cmd_and_fixdep,as_o_S) \
$(cmd_modversions_S) \
$(call echo-cmd,objtool) $(cmd_objtool)
$(call echo-cmd,objtool) $(cmd_objtool) \
$(cmd_modversions_S)
endef
# List module undefined symbols (or empty line if not enabled)

4
tools/objtool/elf.c
View File

@ -26,6 +26,7 @@
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include "elf.h"
#include "warn.h"
@ -358,7 +359,8 @@ struct elf *elf_open(const char *name, int flags)
elf->fd = open(name, flags);
if (elf->fd == -1) {
perror("open");
fprintf(stderr, "objtool: Can't open '%s': %s\n",
name, strerror(errno));
goto err;
}