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linux-zen-server/arch/x86/kernel/cpu/bugs.c

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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 1994 Linus Torvalds
*
* Cyrix stuff, June 1998 by:
* - Rafael R. Reilova (moved everything from head.S),
* <rreilova@ececs.uc.edu>
* - Channing Corn (tests & fixes),
* - Andrew D. Balsa (code cleanup).
*/
#include <linux/init.h>
#include <linux/utsname.h>
#include <linux/cpu.h>
#include <linux/module.h>
#include <linux/nospec.h>
#include <linux/prctl.h>
#include <linux/sched/smt.h>
#include <linux/pgtable.h>
#include <linux/bpf.h>
#include <asm/spec-ctrl.h>
#include <asm/cmdline.h>
#include <asm/bugs.h>
#include <asm/processor.h>
#include <asm/processor-flags.h>
#include <asm/fpu/api.h>
#include <asm/msr.h>
#include <asm/vmx.h>
#include <asm/paravirt.h>
#include <asm/alternative.h>
#include <asm/set_memory.h>
#include <asm/intel-family.h>
#include <asm/e820/api.h>
#include <asm/hypervisor.h>
#include <asm/tlbflush.h>
#include <asm/cpu.h>
#include "cpu.h"
static void __init spectre_v1_select_mitigation(void);
static void __init spectre_v2_select_mitigation(void);
static void __init retbleed_select_mitigation(void);
static void __init spectre_v2_user_select_mitigation(void);
static void __init ssb_select_mitigation(void);
static void __init l1tf_select_mitigation(void);
static void __init mds_select_mitigation(void);
static void __init md_clear_update_mitigation(void);
static void __init md_clear_select_mitigation(void);
static void __init taa_select_mitigation(void);
static void __init mmio_select_mitigation(void);
static void __init srbds_select_mitigation(void);
static void __init l1d_flush_select_mitigation(void);
/* The base value of the SPEC_CTRL MSR without task-specific bits set */
u64 x86_spec_ctrl_base;
EXPORT_SYMBOL_GPL(x86_spec_ctrl_base);
/* The current value of the SPEC_CTRL MSR with task-specific bits set */
DEFINE_PER_CPU(u64, x86_spec_ctrl_current);
EXPORT_SYMBOL_GPL(x86_spec_ctrl_current);
static DEFINE_MUTEX(spec_ctrl_mutex);
/* Update SPEC_CTRL MSR and its cached copy unconditionally */
static void update_spec_ctrl(u64 val)
{
this_cpu_write(x86_spec_ctrl_current, val);
wrmsrl(MSR_IA32_SPEC_CTRL, val);
}
/*
* Keep track of the SPEC_CTRL MSR value for the current task, which may differ
* from x86_spec_ctrl_base due to STIBP/SSB in __speculation_ctrl_update().
*/
void update_spec_ctrl_cond(u64 val)
{
if (this_cpu_read(x86_spec_ctrl_current) == val)
return;
this_cpu_write(x86_spec_ctrl_current, val);
/*
* When KERNEL_IBRS this MSR is written on return-to-user, unless
* forced the update can be delayed until that time.
*/
if (!cpu_feature_enabled(X86_FEATURE_KERNEL_IBRS))
wrmsrl(MSR_IA32_SPEC_CTRL, val);
}
noinstr u64 spec_ctrl_current(void)
{
return this_cpu_read(x86_spec_ctrl_current);
}
EXPORT_SYMBOL_GPL(spec_ctrl_current);
/*
* AMD specific MSR info for Speculative Store Bypass control.
* x86_amd_ls_cfg_ssbd_mask is initialized in identify_boot_cpu().
*/
u64 __ro_after_init x86_amd_ls_cfg_base;
u64 __ro_after_init x86_amd_ls_cfg_ssbd_mask;
/* Control conditional STIBP in switch_to() */
DEFINE_STATIC_KEY_FALSE(switch_to_cond_stibp);
/* Control conditional IBPB in switch_mm() */
DEFINE_STATIC_KEY_FALSE(switch_mm_cond_ibpb);
/* Control unconditional IBPB in switch_mm() */
DEFINE_STATIC_KEY_FALSE(switch_mm_always_ibpb);
/* Control MDS CPU buffer clear before returning to user space */
DEFINE_STATIC_KEY_FALSE(mds_user_clear);
EXPORT_SYMBOL_GPL(mds_user_clear);
/* Control MDS CPU buffer clear before idling (halt, mwait) */
DEFINE_STATIC_KEY_FALSE(mds_idle_clear);
EXPORT_SYMBOL_GPL(mds_idle_clear);
/*
* Controls whether l1d flush based mitigations are enabled,
* based on hw features and admin setting via boot parameter
* defaults to false
*/
DEFINE_STATIC_KEY_FALSE(switch_mm_cond_l1d_flush);
/* Controls CPU Fill buffer clear before KVM guest MMIO accesses */
DEFINE_STATIC_KEY_FALSE(mmio_stale_data_clear);
EXPORT_SYMBOL_GPL(mmio_stale_data_clear);
void __init check_bugs(void)
{
identify_boot_cpu();
/*
* identify_boot_cpu() initialized SMT support information, let the
* core code know.
*/
cpu_smt_check_topology();
if (!IS_ENABLED(CONFIG_SMP)) {
pr_info("CPU: ");
print_cpu_info(&boot_cpu_data);
}
/*
* Read the SPEC_CTRL MSR to account for reserved bits which may
* have unknown values. AMD64_LS_CFG MSR is cached in the early AMD
* init code as it is not enumerated and depends on the family.
*/
if (cpu_feature_enabled(X86_FEATURE_MSR_SPEC_CTRL)) {
rdmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
/*
* Previously running kernel (kexec), may have some controls
* turned ON. Clear them and let the mitigations setup below
* rediscover them based on configuration.
*/
x86_spec_ctrl_base &= ~SPEC_CTRL_MITIGATIONS_MASK;
}
/* Select the proper CPU mitigations before patching alternatives: */
spectre_v1_select_mitigation();
spectre_v2_select_mitigation();
/*
* retbleed_select_mitigation() relies on the state set by
* spectre_v2_select_mitigation(); specifically it wants to know about
* spectre_v2=ibrs.
*/
retbleed_select_mitigation();
/*
* spectre_v2_user_select_mitigation() relies on the state set by
* retbleed_select_mitigation(); specifically the STIBP selection is
* forced for UNRET or IBPB.
*/
spectre_v2_user_select_mitigation();
ssb_select_mitigation();
l1tf_select_mitigation();
md_clear_select_mitigation();
srbds_select_mitigation();
l1d_flush_select_mitigation();
arch_smt_update();
#ifdef CONFIG_X86_32
/*
* Check whether we are able to run this kernel safely on SMP.
*
* - i386 is no longer supported.
* - In order to run on anything without a TSC, we need to be
* compiled for a i486.
*/
if (boot_cpu_data.x86 < 4)
panic("Kernel requires i486+ for 'invlpg' and other features");
init_utsname()->machine[1] =
'0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86);
alternative_instructions();
fpu__init_check_bugs();
#else /* CONFIG_X86_64 */
alternative_instructions();
/*
* Make sure the first 2MB area is not mapped by huge pages
* There are typically fixed size MTRRs in there and overlapping
* MTRRs into large pages causes slow downs.
*
* Right now we don't do that with gbpages because there seems
* very little benefit for that case.
*/
if (!direct_gbpages)
set_memory_4k((unsigned long)__va(0), 1);
#endif
}
/*
* NOTE: This function is *only* called for SVM, since Intel uses
* MSR_IA32_SPEC_CTRL for SSBD.
*/
void
x86_virt_spec_ctrl(u64 guest_virt_spec_ctrl, bool setguest)
{
u64 guestval, hostval;
struct thread_info *ti = current_thread_info();
/*
* If SSBD is not handled in MSR_SPEC_CTRL on AMD, update
* MSR_AMD64_L2_CFG or MSR_VIRT_SPEC_CTRL if supported.
*/
if (!static_cpu_has(X86_FEATURE_LS_CFG_SSBD) &&
!static_cpu_has(X86_FEATURE_VIRT_SSBD))
return;
/*
* If the host has SSBD mitigation enabled, force it in the host's
* virtual MSR value. If its not permanently enabled, evaluate
* current's TIF_SSBD thread flag.
*/
if (static_cpu_has(X86_FEATURE_SPEC_STORE_BYPASS_DISABLE))
hostval = SPEC_CTRL_SSBD;
else
hostval = ssbd_tif_to_spec_ctrl(ti->flags);
/* Sanitize the guest value */
guestval = guest_virt_spec_ctrl & SPEC_CTRL_SSBD;
if (hostval != guestval) {
unsigned long tif;
tif = setguest ? ssbd_spec_ctrl_to_tif(guestval) :
ssbd_spec_ctrl_to_tif(hostval);
speculation_ctrl_update(tif);
}
}
EXPORT_SYMBOL_GPL(x86_virt_spec_ctrl);
static void x86_amd_ssb_disable(void)
{
u64 msrval = x86_amd_ls_cfg_base | x86_amd_ls_cfg_ssbd_mask;
if (boot_cpu_has(X86_FEATURE_VIRT_SSBD))
wrmsrl(MSR_AMD64_VIRT_SPEC_CTRL, SPEC_CTRL_SSBD);
else if (boot_cpu_has(X86_FEATURE_LS_CFG_SSBD))
wrmsrl(MSR_AMD64_LS_CFG, msrval);
}
#undef pr_fmt
#define pr_fmt(fmt) "MDS: " fmt
/* Default mitigation for MDS-affected CPUs */
static enum mds_mitigations mds_mitigation __ro_after_init = MDS_MITIGATION_FULL;
static bool mds_nosmt __ro_after_init = false;
static const char * const mds_strings[] = {
[MDS_MITIGATION_OFF] = "Vulnerable",
[MDS_MITIGATION_FULL] = "Mitigation: Clear CPU buffers",
[MDS_MITIGATION_VMWERV] = "Vulnerable: Clear CPU buffers attempted, no microcode",
};
static void __init mds_select_mitigation(void)
{
if (!boot_cpu_has_bug(X86_BUG_MDS) || cpu_mitigations_off()) {
mds_mitigation = MDS_MITIGATION_OFF;
return;
}
if (mds_mitigation == MDS_MITIGATION_FULL) {
if (!boot_cpu_has(X86_FEATURE_MD_CLEAR))
mds_mitigation = MDS_MITIGATION_VMWERV;
static_branch_enable(&mds_user_clear);
if (!boot_cpu_has(X86_BUG_MSBDS_ONLY) &&
(mds_nosmt || cpu_mitigations_auto_nosmt()))
cpu_smt_disable(false);
}
}
static int __init mds_cmdline(char *str)
{
if (!boot_cpu_has_bug(X86_BUG_MDS))
return 0;
if (!str)
return -EINVAL;
if (!strcmp(str, "off"))
mds_mitigation = MDS_MITIGATION_OFF;
else if (!strcmp(str, "full"))
mds_mitigation = MDS_MITIGATION_FULL;
else if (!strcmp(str, "full,nosmt")) {
mds_mitigation = MDS_MITIGATION_FULL;
mds_nosmt = true;
}
return 0;
}
early_param("mds", mds_cmdline);
#undef pr_fmt
#define pr_fmt(fmt) "TAA: " fmt
enum taa_mitigations {
TAA_MITIGATION_OFF,
TAA_MITIGATION_UCODE_NEEDED,
TAA_MITIGATION_VERW,
TAA_MITIGATION_TSX_DISABLED,
};
/* Default mitigation for TAA-affected CPUs */
static enum taa_mitigations taa_mitigation __ro_after_init = TAA_MITIGATION_VERW;
static bool taa_nosmt __ro_after_init;
static const char * const taa_strings[] = {
[TAA_MITIGATION_OFF] = "Vulnerable",
[TAA_MITIGATION_UCODE_NEEDED] = "Vulnerable: Clear CPU buffers attempted, no microcode",
[TAA_MITIGATION_VERW] = "Mitigation: Clear CPU buffers",
[TAA_MITIGATION_TSX_DISABLED] = "Mitigation: TSX disabled",
};
static void __init taa_select_mitigation(void)
{
u64 ia32_cap;
if (!boot_cpu_has_bug(X86_BUG_TAA)) {
taa_mitigation = TAA_MITIGATION_OFF;
return;
}
/* TSX previously disabled by tsx=off */
if (!boot_cpu_has(X86_FEATURE_RTM)) {
taa_mitigation = TAA_MITIGATION_TSX_DISABLED;
return;
}
if (cpu_mitigations_off()) {
taa_mitigation = TAA_MITIGATION_OFF;
return;
}
/*
* TAA mitigation via VERW is turned off if both
* tsx_async_abort=off and mds=off are specified.
*/
if (taa_mitigation == TAA_MITIGATION_OFF &&
mds_mitigation == MDS_MITIGATION_OFF)
return;
if (boot_cpu_has(X86_FEATURE_MD_CLEAR))
taa_mitigation = TAA_MITIGATION_VERW;
else
taa_mitigation = TAA_MITIGATION_UCODE_NEEDED;
/*
* VERW doesn't clear the CPU buffers when MD_CLEAR=1 and MDS_NO=1.
* A microcode update fixes this behavior to clear CPU buffers. It also
* adds support for MSR_IA32_TSX_CTRL which is enumerated by the
* ARCH_CAP_TSX_CTRL_MSR bit.
*
* On MDS_NO=1 CPUs if ARCH_CAP_TSX_CTRL_MSR is not set, microcode
* update is required.
*/
ia32_cap = x86_read_arch_cap_msr();
if ( (ia32_cap & ARCH_CAP_MDS_NO) &&
!(ia32_cap & ARCH_CAP_TSX_CTRL_MSR))
taa_mitigation = TAA_MITIGATION_UCODE_NEEDED;
/*
* TSX is enabled, select alternate mitigation for TAA which is
* the same as MDS. Enable MDS static branch to clear CPU buffers.
*
* For guests that can't determine whether the correct microcode is
* present on host, enable the mitigation for UCODE_NEEDED as well.
*/
static_branch_enable(&mds_user_clear);
if (taa_nosmt || cpu_mitigations_auto_nosmt())
cpu_smt_disable(false);
}
static int __init tsx_async_abort_parse_cmdline(char *str)
{
if (!boot_cpu_has_bug(X86_BUG_TAA))
return 0;
if (!str)
return -EINVAL;
if (!strcmp(str, "off")) {
taa_mitigation = TAA_MITIGATION_OFF;
} else if (!strcmp(str, "full")) {
taa_mitigation = TAA_MITIGATION_VERW;
} else if (!strcmp(str, "full,nosmt")) {
taa_mitigation = TAA_MITIGATION_VERW;
taa_nosmt = true;
}
return 0;
}
early_param("tsx_async_abort", tsx_async_abort_parse_cmdline);
#undef pr_fmt
#define pr_fmt(fmt) "MMIO Stale Data: " fmt
enum mmio_mitigations {
MMIO_MITIGATION_OFF,
MMIO_MITIGATION_UCODE_NEEDED,
MMIO_MITIGATION_VERW,
};
/* Default mitigation for Processor MMIO Stale Data vulnerabilities */
static enum mmio_mitigations mmio_mitigation __ro_after_init = MMIO_MITIGATION_VERW;
static bool mmio_nosmt __ro_after_init = false;
static const char * const mmio_strings[] = {
[MMIO_MITIGATION_OFF] = "Vulnerable",
[MMIO_MITIGATION_UCODE_NEEDED] = "Vulnerable: Clear CPU buffers attempted, no microcode",
[MMIO_MITIGATION_VERW] = "Mitigation: Clear CPU buffers",
};
static void __init mmio_select_mitigation(void)
{
u64 ia32_cap;
if (!boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA) ||
boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN) ||
cpu_mitigations_off()) {
mmio_mitigation = MMIO_MITIGATION_OFF;
return;
}
if (mmio_mitigation == MMIO_MITIGATION_OFF)
return;
ia32_cap = x86_read_arch_cap_msr();
/*
* Enable CPU buffer clear mitigation for host and VMM, if also affected
* by MDS or TAA. Otherwise, enable mitigation for VMM only.
*/
if (boot_cpu_has_bug(X86_BUG_MDS) || (boot_cpu_has_bug(X86_BUG_TAA) &&
boot_cpu_has(X86_FEATURE_RTM)))
static_branch_enable(&mds_user_clear);
else
static_branch_enable(&mmio_stale_data_clear);
/*
* If Processor-MMIO-Stale-Data bug is present and Fill Buffer data can
* be propagated to uncore buffers, clearing the Fill buffers on idle
* is required irrespective of SMT state.
*/
if (!(ia32_cap & ARCH_CAP_FBSDP_NO))
static_branch_enable(&mds_idle_clear);
/*
* Check if the system has the right microcode.
*
* CPU Fill buffer clear mitigation is enumerated by either an explicit
* FB_CLEAR or by the presence of both MD_CLEAR and L1D_FLUSH on MDS
* affected systems.
*/
if ((ia32_cap & ARCH_CAP_FB_CLEAR) ||
(boot_cpu_has(X86_FEATURE_MD_CLEAR) &&
boot_cpu_has(X86_FEATURE_FLUSH_L1D) &&
!(ia32_cap & ARCH_CAP_MDS_NO)))
mmio_mitigation = MMIO_MITIGATION_VERW;
else
mmio_mitigation = MMIO_MITIGATION_UCODE_NEEDED;
if (mmio_nosmt || cpu_mitigations_auto_nosmt())
cpu_smt_disable(false);
}
static int __init mmio_stale_data_parse_cmdline(char *str)
{
if (!boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA))
return 0;
if (!str)
return -EINVAL;
if (!strcmp(str, "off")) {
mmio_mitigation = MMIO_MITIGATION_OFF;
} else if (!strcmp(str, "full")) {
mmio_mitigation = MMIO_MITIGATION_VERW;
} else if (!strcmp(str, "full,nosmt")) {
mmio_mitigation = MMIO_MITIGATION_VERW;
mmio_nosmt = true;
}
return 0;
}
early_param("mmio_stale_data", mmio_stale_data_parse_cmdline);
#undef pr_fmt
#define pr_fmt(fmt) "" fmt
static void __init md_clear_update_mitigation(void)
{
if (cpu_mitigations_off())
return;
if (!static_key_enabled(&mds_user_clear))
goto out;
/*
* mds_user_clear is now enabled. Update MDS, TAA and MMIO Stale Data
* mitigation, if necessary.
*/
if (mds_mitigation == MDS_MITIGATION_OFF &&
boot_cpu_has_bug(X86_BUG_MDS)) {
mds_mitigation = MDS_MITIGATION_FULL;
mds_select_mitigation();
}
if (taa_mitigation == TAA_MITIGATION_OFF &&
boot_cpu_has_bug(X86_BUG_TAA)) {
taa_mitigation = TAA_MITIGATION_VERW;
taa_select_mitigation();
}
if (mmio_mitigation == MMIO_MITIGATION_OFF &&
boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA)) {
mmio_mitigation = MMIO_MITIGATION_VERW;
mmio_select_mitigation();
}
out:
if (boot_cpu_has_bug(X86_BUG_MDS))
pr_info("MDS: %s\n", mds_strings[mds_mitigation]);
if (boot_cpu_has_bug(X86_BUG_TAA))
pr_info("TAA: %s\n", taa_strings[taa_mitigation]);
if (boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA))
pr_info("MMIO Stale Data: %s\n", mmio_strings[mmio_mitigation]);
else if (boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN))
pr_info("MMIO Stale Data: Unknown: No mitigations\n");
}
static void __init md_clear_select_mitigation(void)
{
mds_select_mitigation();
taa_select_mitigation();
mmio_select_mitigation();
/*
* As MDS, TAA and MMIO Stale Data mitigations are inter-related, update
* and print their mitigation after MDS, TAA and MMIO Stale Data
* mitigation selection is done.
*/
md_clear_update_mitigation();
}
#undef pr_fmt
#define pr_fmt(fmt) "SRBDS: " fmt
enum srbds_mitigations {
SRBDS_MITIGATION_OFF,
SRBDS_MITIGATION_UCODE_NEEDED,
SRBDS_MITIGATION_FULL,
SRBDS_MITIGATION_TSX_OFF,
SRBDS_MITIGATION_HYPERVISOR,
};
static enum srbds_mitigations srbds_mitigation __ro_after_init = SRBDS_MITIGATION_FULL;
static const char * const srbds_strings[] = {
[SRBDS_MITIGATION_OFF] = "Vulnerable",
[SRBDS_MITIGATION_UCODE_NEEDED] = "Vulnerable: No microcode",
[SRBDS_MITIGATION_FULL] = "Mitigation: Microcode",
[SRBDS_MITIGATION_TSX_OFF] = "Mitigation: TSX disabled",
[SRBDS_MITIGATION_HYPERVISOR] = "Unknown: Dependent on hypervisor status",
};
static bool srbds_off;
void update_srbds_msr(void)
{
u64 mcu_ctrl;
if (!boot_cpu_has_bug(X86_BUG_SRBDS))
return;
if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
return;
if (srbds_mitigation == SRBDS_MITIGATION_UCODE_NEEDED)
return;
/*
* A MDS_NO CPU for which SRBDS mitigation is not needed due to TSX
* being disabled and it hasn't received the SRBDS MSR microcode.
*/
if (!boot_cpu_has(X86_FEATURE_SRBDS_CTRL))
return;
rdmsrl(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl);
switch (srbds_mitigation) {
case SRBDS_MITIGATION_OFF:
case SRBDS_MITIGATION_TSX_OFF:
mcu_ctrl |= RNGDS_MITG_DIS;
break;
case SRBDS_MITIGATION_FULL:
mcu_ctrl &= ~RNGDS_MITG_DIS;
break;
default:
break;
}
wrmsrl(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl);
}
static void __init srbds_select_mitigation(void)
{
u64 ia32_cap;
if (!boot_cpu_has_bug(X86_BUG_SRBDS))
return;
/*
* Check to see if this is one of the MDS_NO systems supporting TSX that
* are only exposed to SRBDS when TSX is enabled or when CPU is affected
* by Processor MMIO Stale Data vulnerability.
*/
ia32_cap = x86_read_arch_cap_msr();
if ((ia32_cap & ARCH_CAP_MDS_NO) && !boot_cpu_has(X86_FEATURE_RTM) &&
!boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA))
srbds_mitigation = SRBDS_MITIGATION_TSX_OFF;
else if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
srbds_mitigation = SRBDS_MITIGATION_HYPERVISOR;
else if (!boot_cpu_has(X86_FEATURE_SRBDS_CTRL))
srbds_mitigation = SRBDS_MITIGATION_UCODE_NEEDED;
else if (cpu_mitigations_off() || srbds_off)
srbds_mitigation = SRBDS_MITIGATION_OFF;
update_srbds_msr();
pr_info("%s\n", srbds_strings[srbds_mitigation]);
}
static int __init srbds_parse_cmdline(char *str)
{
if (!str)
return -EINVAL;
if (!boot_cpu_has_bug(X86_BUG_SRBDS))
return 0;
srbds_off = !strcmp(str, "off");
return 0;
}
early_param("srbds", srbds_parse_cmdline);
#undef pr_fmt
#define pr_fmt(fmt) "L1D Flush : " fmt
enum l1d_flush_mitigations {
L1D_FLUSH_OFF = 0,
L1D_FLUSH_ON,
};
static enum l1d_flush_mitigations l1d_flush_mitigation __initdata = L1D_FLUSH_OFF;
static void __init l1d_flush_select_mitigation(void)
{
if (!l1d_flush_mitigation || !boot_cpu_has(X86_FEATURE_FLUSH_L1D))
return;
static_branch_enable(&switch_mm_cond_l1d_flush);
pr_info("Conditional flush on switch_mm() enabled\n");
}
static int __init l1d_flush_parse_cmdline(char *str)
{
if (!strcmp(str, "on"))
l1d_flush_mitigation = L1D_FLUSH_ON;
return 0;
}
early_param("l1d_flush", l1d_flush_parse_cmdline);
#undef pr_fmt
#define pr_fmt(fmt) "Spectre V1 : " fmt
enum spectre_v1_mitigation {
SPECTRE_V1_MITIGATION_NONE,
SPECTRE_V1_MITIGATION_AUTO,
};
static enum spectre_v1_mitigation spectre_v1_mitigation __ro_after_init =
SPECTRE_V1_MITIGATION_AUTO;
static const char * const spectre_v1_strings[] = {
[SPECTRE_V1_MITIGATION_NONE] = "Vulnerable: __user pointer sanitization and usercopy barriers only; no swapgs barriers",
[SPECTRE_V1_MITIGATION_AUTO] = "Mitigation: usercopy/swapgs barriers and __user pointer sanitization",
};
/*
* Does SMAP provide full mitigation against speculative kernel access to
* userspace?
*/
static bool smap_works_speculatively(void)
{
if (!boot_cpu_has(X86_FEATURE_SMAP))
return false;
/*
* On CPUs which are vulnerable to Meltdown, SMAP does not
* prevent speculative access to user data in the L1 cache.
* Consider SMAP to be non-functional as a mitigation on these
* CPUs.
*/
if (boot_cpu_has(X86_BUG_CPU_MELTDOWN))
return false;
return true;
}
static void __init spectre_v1_select_mitigation(void)
{
if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V1) || cpu_mitigations_off()) {
spectre_v1_mitigation = SPECTRE_V1_MITIGATION_NONE;
return;
}
if (spectre_v1_mitigation == SPECTRE_V1_MITIGATION_AUTO) {
/*
* With Spectre v1, a user can speculatively control either
* path of a conditional swapgs with a user-controlled GS
* value. The mitigation is to add lfences to both code paths.
*
* If FSGSBASE is enabled, the user can put a kernel address in
* GS, in which case SMAP provides no protection.
*
* If FSGSBASE is disabled, the user can only put a user space
* address in GS. That makes an attack harder, but still
* possible if there's no SMAP protection.
*/
if (boot_cpu_has(X86_FEATURE_FSGSBASE) ||
!smap_works_speculatively()) {
/*
* Mitigation can be provided from SWAPGS itself or
* PTI as the CR3 write in the Meltdown mitigation
* is serializing.
*
* If neither is there, mitigate with an LFENCE to
* stop speculation through swapgs.
*/
if (boot_cpu_has_bug(X86_BUG_SWAPGS) &&
!boot_cpu_has(X86_FEATURE_PTI))
setup_force_cpu_cap(X86_FEATURE_FENCE_SWAPGS_USER);
/*
* Enable lfences in the kernel entry (non-swapgs)
* paths, to prevent user entry from speculatively
* skipping swapgs.
*/
setup_force_cpu_cap(X86_FEATURE_FENCE_SWAPGS_KERNEL);
}
}
pr_info("%s\n", spectre_v1_strings[spectre_v1_mitigation]);
}
static int __init nospectre_v1_cmdline(char *str)
{
spectre_v1_mitigation = SPECTRE_V1_MITIGATION_NONE;
return 0;
}
early_param("nospectre_v1", nospectre_v1_cmdline);
static enum spectre_v2_mitigation spectre_v2_enabled __ro_after_init =
SPECTRE_V2_NONE;
#undef pr_fmt
#define pr_fmt(fmt) "RETBleed: " fmt
enum retbleed_mitigation {
RETBLEED_MITIGATION_NONE,
RETBLEED_MITIGATION_UNRET,
RETBLEED_MITIGATION_IBPB,
RETBLEED_MITIGATION_IBRS,
RETBLEED_MITIGATION_EIBRS,
RETBLEED_MITIGATION_STUFF,
};
enum retbleed_mitigation_cmd {
RETBLEED_CMD_OFF,
RETBLEED_CMD_AUTO,
RETBLEED_CMD_UNRET,
RETBLEED_CMD_IBPB,
RETBLEED_CMD_STUFF,
};
static const char * const retbleed_strings[] = {
[RETBLEED_MITIGATION_NONE] = "Vulnerable",
[RETBLEED_MITIGATION_UNRET] = "Mitigation: untrained return thunk",
[RETBLEED_MITIGATION_IBPB] = "Mitigation: IBPB",
[RETBLEED_MITIGATION_IBRS] = "Mitigation: IBRS",
[RETBLEED_MITIGATION_EIBRS] = "Mitigation: Enhanced IBRS",
[RETBLEED_MITIGATION_STUFF] = "Mitigation: Stuffing",
};
static enum retbleed_mitigation retbleed_mitigation __ro_after_init =
RETBLEED_MITIGATION_NONE;
static enum retbleed_mitigation_cmd retbleed_cmd __ro_after_init =
RETBLEED_CMD_AUTO;
static int __ro_after_init retbleed_nosmt = false;
static int __init retbleed_parse_cmdline(char *str)
{
if (!str)
return -EINVAL;
while (str) {
char *next = strchr(str, ',');
if (next) {
*next = 0;
next++;
}
if (!strcmp(str, "off")) {
retbleed_cmd = RETBLEED_CMD_OFF;
} else if (!strcmp(str, "auto")) {
retbleed_cmd = RETBLEED_CMD_AUTO;
} else if (!strcmp(str, "unret")) {
retbleed_cmd = RETBLEED_CMD_UNRET;
} else if (!strcmp(str, "ibpb")) {
retbleed_cmd = RETBLEED_CMD_IBPB;
} else if (!strcmp(str, "stuff")) {
retbleed_cmd = RETBLEED_CMD_STUFF;
} else if (!strcmp(str, "nosmt")) {
retbleed_nosmt = true;
} else if (!strcmp(str, "force")) {
setup_force_cpu_bug(X86_BUG_RETBLEED);
} else {
pr_err("Ignoring unknown retbleed option (%s).", str);
}
str = next;
}
return 0;
}
early_param("retbleed", retbleed_parse_cmdline);
#define RETBLEED_UNTRAIN_MSG "WARNING: BTB untrained return thunk mitigation is only effective on AMD/Hygon!\n"
#define RETBLEED_INTEL_MSG "WARNING: Spectre v2 mitigation leaves CPU vulnerable to RETBleed attacks, data leaks possible!\n"
static void __init retbleed_select_mitigation(void)
{
bool mitigate_smt = false;
if (!boot_cpu_has_bug(X86_BUG_RETBLEED) || cpu_mitigations_off())
return;
switch (retbleed_cmd) {
case RETBLEED_CMD_OFF:
return;
case RETBLEED_CMD_UNRET:
if (IS_ENABLED(CONFIG_CPU_UNRET_ENTRY)) {
retbleed_mitigation = RETBLEED_MITIGATION_UNRET;
} else {
pr_err("WARNING: kernel not compiled with CPU_UNRET_ENTRY.\n");
goto do_cmd_auto;
}
break;
case RETBLEED_CMD_IBPB:
if (!boot_cpu_has(X86_FEATURE_IBPB)) {
pr_err("WARNING: CPU does not support IBPB.\n");
goto do_cmd_auto;
} else if (IS_ENABLED(CONFIG_CPU_IBPB_ENTRY)) {
retbleed_mitigation = RETBLEED_MITIGATION_IBPB;
} else {
pr_err("WARNING: kernel not compiled with CPU_IBPB_ENTRY.\n");
goto do_cmd_auto;
}
break;
case RETBLEED_CMD_STUFF:
if (IS_ENABLED(CONFIG_CALL_DEPTH_TRACKING) &&
spectre_v2_enabled == SPECTRE_V2_RETPOLINE) {
retbleed_mitigation = RETBLEED_MITIGATION_STUFF;
} else {
if (IS_ENABLED(CONFIG_CALL_DEPTH_TRACKING))
pr_err("WARNING: retbleed=stuff depends on spectre_v2=retpoline\n");
else
pr_err("WARNING: kernel not compiled with CALL_DEPTH_TRACKING.\n");
goto do_cmd_auto;
}
break;
do_cmd_auto:
case RETBLEED_CMD_AUTO:
default:
if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) {
if (IS_ENABLED(CONFIG_CPU_UNRET_ENTRY))
retbleed_mitigation = RETBLEED_MITIGATION_UNRET;
else if (IS_ENABLED(CONFIG_CPU_IBPB_ENTRY) && boot_cpu_has(X86_FEATURE_IBPB))
retbleed_mitigation = RETBLEED_MITIGATION_IBPB;
}
/*
* The Intel mitigation (IBRS or eIBRS) was already selected in
* spectre_v2_select_mitigation(). 'retbleed_mitigation' will
* be set accordingly below.
*/
break;
}
switch (retbleed_mitigation) {
case RETBLEED_MITIGATION_UNRET:
setup_force_cpu_cap(X86_FEATURE_RETHUNK);
setup_force_cpu_cap(X86_FEATURE_UNRET);
if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD &&
boot_cpu_data.x86_vendor != X86_VENDOR_HYGON)
pr_err(RETBLEED_UNTRAIN_MSG);
mitigate_smt = true;
break;
case RETBLEED_MITIGATION_IBPB:
setup_force_cpu_cap(X86_FEATURE_ENTRY_IBPB);
mitigate_smt = true;
break;
case RETBLEED_MITIGATION_STUFF:
setup_force_cpu_cap(X86_FEATURE_RETHUNK);
setup_force_cpu_cap(X86_FEATURE_CALL_DEPTH);
x86_set_skl_return_thunk();
break;
default:
break;
}
if (mitigate_smt && !boot_cpu_has(X86_FEATURE_STIBP) &&
(retbleed_nosmt || cpu_mitigations_auto_nosmt()))
cpu_smt_disable(false);
/*
* Let IBRS trump all on Intel without affecting the effects of the
* retbleed= cmdline option except for call depth based stuffing
*/
if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) {
switch (spectre_v2_enabled) {
case SPECTRE_V2_IBRS:
retbleed_mitigation = RETBLEED_MITIGATION_IBRS;
break;
case SPECTRE_V2_EIBRS:
case SPECTRE_V2_EIBRS_RETPOLINE:
case SPECTRE_V2_EIBRS_LFENCE:
retbleed_mitigation = RETBLEED_MITIGATION_EIBRS;
break;
default:
if (retbleed_mitigation != RETBLEED_MITIGATION_STUFF)
pr_err(RETBLEED_INTEL_MSG);
}
}
pr_info("%s\n", retbleed_strings[retbleed_mitigation]);
}
#undef pr_fmt
#define pr_fmt(fmt) "Spectre V2 : " fmt
static enum spectre_v2_user_mitigation spectre_v2_user_stibp __ro_after_init =
SPECTRE_V2_USER_NONE;
static enum spectre_v2_user_mitigation spectre_v2_user_ibpb __ro_after_init =
SPECTRE_V2_USER_NONE;
#ifdef CONFIG_RETPOLINE
static bool spectre_v2_bad_module;
bool retpoline_module_ok(bool has_retpoline)
{
if (spectre_v2_enabled == SPECTRE_V2_NONE || has_retpoline)
return true;
pr_err("System may be vulnerable to spectre v2\n");
spectre_v2_bad_module = true;
return false;
}
static inline const char *spectre_v2_module_string(void)
{
return spectre_v2_bad_module ? " - vulnerable module loaded" : "";
}
#else
static inline const char *spectre_v2_module_string(void) { return ""; }
#endif
#define SPECTRE_V2_LFENCE_MSG "WARNING: LFENCE mitigation is not recommended for this CPU, data leaks possible!\n"
#define SPECTRE_V2_EIBRS_EBPF_MSG "WARNING: Unprivileged eBPF is enabled with eIBRS on, data leaks possible via Spectre v2 BHB attacks!\n"
#define SPECTRE_V2_EIBRS_LFENCE_EBPF_SMT_MSG "WARNING: Unprivileged eBPF is enabled with eIBRS+LFENCE mitigation and SMT, data leaks possible via Spectre v2 BHB attacks!\n"
#define SPECTRE_V2_IBRS_PERF_MSG "WARNING: IBRS mitigation selected on Enhanced IBRS CPU, this may cause unnecessary performance loss\n"
#ifdef CONFIG_BPF_SYSCALL
void unpriv_ebpf_notify(int new_state)
{
if (new_state)
return;
/* Unprivileged eBPF is enabled */
switch (spectre_v2_enabled) {
case SPECTRE_V2_EIBRS:
pr_err(SPECTRE_V2_EIBRS_EBPF_MSG);
break;
case SPECTRE_V2_EIBRS_LFENCE:
if (sched_smt_active())
pr_err(SPECTRE_V2_EIBRS_LFENCE_EBPF_SMT_MSG);
break;
default:
break;
}
}
#endif
static inline bool match_option(const char *arg, int arglen, const char *opt)
{
int len = strlen(opt);
return len == arglen && !strncmp(arg, opt, len);
}
/* The kernel command line selection for spectre v2 */
enum spectre_v2_mitigation_cmd {
SPECTRE_V2_CMD_NONE,
SPECTRE_V2_CMD_AUTO,
SPECTRE_V2_CMD_FORCE,
SPECTRE_V2_CMD_RETPOLINE,
SPECTRE_V2_CMD_RETPOLINE_GENERIC,
SPECTRE_V2_CMD_RETPOLINE_LFENCE,
SPECTRE_V2_CMD_EIBRS,
SPECTRE_V2_CMD_EIBRS_RETPOLINE,
SPECTRE_V2_CMD_EIBRS_LFENCE,
SPECTRE_V2_CMD_IBRS,
};
enum spectre_v2_user_cmd {
SPECTRE_V2_USER_CMD_NONE,
SPECTRE_V2_USER_CMD_AUTO,
SPECTRE_V2_USER_CMD_FORCE,
SPECTRE_V2_USER_CMD_PRCTL,
SPECTRE_V2_USER_CMD_PRCTL_IBPB,
SPECTRE_V2_USER_CMD_SECCOMP,
SPECTRE_V2_USER_CMD_SECCOMP_IBPB,
};
static const char * const spectre_v2_user_strings[] = {
[SPECTRE_V2_USER_NONE] = "User space: Vulnerable",
[SPECTRE_V2_USER_STRICT] = "User space: Mitigation: STIBP protection",
[SPECTRE_V2_USER_STRICT_PREFERRED] = "User space: Mitigation: STIBP always-on protection",
[SPECTRE_V2_USER_PRCTL] = "User space: Mitigation: STIBP via prctl",
[SPECTRE_V2_USER_SECCOMP] = "User space: Mitigation: STIBP via seccomp and prctl",
};
static const struct {
const char *option;
enum spectre_v2_user_cmd cmd;
bool secure;
} v2_user_options[] __initconst = {
{ "auto", SPECTRE_V2_USER_CMD_AUTO, false },
{ "off", SPECTRE_V2_USER_CMD_NONE, false },
{ "on", SPECTRE_V2_USER_CMD_FORCE, true },
{ "prctl", SPECTRE_V2_USER_CMD_PRCTL, false },
{ "prctl,ibpb", SPECTRE_V2_USER_CMD_PRCTL_IBPB, false },
{ "seccomp", SPECTRE_V2_USER_CMD_SECCOMP, false },
{ "seccomp,ibpb", SPECTRE_V2_USER_CMD_SECCOMP_IBPB, false },
};
static void __init spec_v2_user_print_cond(const char *reason, bool secure)
{
if (boot_cpu_has_bug(X86_BUG_SPECTRE_V2) != secure)
pr_info("spectre_v2_user=%s forced on command line.\n", reason);
}
static __ro_after_init enum spectre_v2_mitigation_cmd spectre_v2_cmd;
static enum spectre_v2_user_cmd __init
spectre_v2_parse_user_cmdline(void)
{
char arg[20];
int ret, i;
switch (spectre_v2_cmd) {
case SPECTRE_V2_CMD_NONE:
return SPECTRE_V2_USER_CMD_NONE;
case SPECTRE_V2_CMD_FORCE:
return SPECTRE_V2_USER_CMD_FORCE;
default:
break;
}
ret = cmdline_find_option(boot_command_line, "spectre_v2_user",
arg, sizeof(arg));
if (ret < 0)
return SPECTRE_V2_USER_CMD_AUTO;
for (i = 0; i < ARRAY_SIZE(v2_user_options); i++) {
if (match_option(arg, ret, v2_user_options[i].option)) {
spec_v2_user_print_cond(v2_user_options[i].option,
v2_user_options[i].secure);
return v2_user_options[i].cmd;
}
}
pr_err("Unknown user space protection option (%s). Switching to AUTO select\n", arg);
return SPECTRE_V2_USER_CMD_AUTO;
}
static inline bool spectre_v2_in_eibrs_mode(enum spectre_v2_mitigation mode)
{
return mode == SPECTRE_V2_EIBRS ||
mode == SPECTRE_V2_EIBRS_RETPOLINE ||
mode == SPECTRE_V2_EIBRS_LFENCE;
}
static inline bool spectre_v2_in_ibrs_mode(enum spectre_v2_mitigation mode)
{
return spectre_v2_in_eibrs_mode(mode) || mode == SPECTRE_V2_IBRS;
}
static void __init
spectre_v2_user_select_mitigation(void)
{
enum spectre_v2_user_mitigation mode = SPECTRE_V2_USER_NONE;
bool smt_possible = IS_ENABLED(CONFIG_SMP);
enum spectre_v2_user_cmd cmd;
if (!boot_cpu_has(X86_FEATURE_IBPB) && !boot_cpu_has(X86_FEATURE_STIBP))
return;
if (cpu_smt_control == CPU_SMT_FORCE_DISABLED ||
cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
smt_possible = false;
cmd = spectre_v2_parse_user_cmdline();
switch (cmd) {
case SPECTRE_V2_USER_CMD_NONE:
goto set_mode;
case SPECTRE_V2_USER_CMD_FORCE:
mode = SPECTRE_V2_USER_STRICT;
break;
case SPECTRE_V2_USER_CMD_AUTO:
case SPECTRE_V2_USER_CMD_PRCTL:
case SPECTRE_V2_USER_CMD_PRCTL_IBPB:
mode = SPECTRE_V2_USER_PRCTL;
break;
case SPECTRE_V2_USER_CMD_SECCOMP:
case SPECTRE_V2_USER_CMD_SECCOMP_IBPB:
if (IS_ENABLED(CONFIG_SECCOMP))
mode = SPECTRE_V2_USER_SECCOMP;
else
mode = SPECTRE_V2_USER_PRCTL;
break;
}
/* Initialize Indirect Branch Prediction Barrier */
if (boot_cpu_has(X86_FEATURE_IBPB)) {
setup_force_cpu_cap(X86_FEATURE_USE_IBPB);
spectre_v2_user_ibpb = mode;
switch (cmd) {
case SPECTRE_V2_USER_CMD_FORCE:
case SPECTRE_V2_USER_CMD_PRCTL_IBPB:
case SPECTRE_V2_USER_CMD_SECCOMP_IBPB:
static_branch_enable(&switch_mm_always_ibpb);
spectre_v2_user_ibpb = SPECTRE_V2_USER_STRICT;
break;
case SPECTRE_V2_USER_CMD_PRCTL:
case SPECTRE_V2_USER_CMD_AUTO:
case SPECTRE_V2_USER_CMD_SECCOMP:
static_branch_enable(&switch_mm_cond_ibpb);
break;
default:
break;
}
pr_info("mitigation: Enabling %s Indirect Branch Prediction Barrier\n",
static_key_enabled(&switch_mm_always_ibpb) ?
"always-on" : "conditional");
}
/*
* If no STIBP, enhanced IBRS is enabled, or SMT impossible, STIBP
* is not required.
*
* Enhanced IBRS also protects against cross-thread branch target
* injection in user-mode as the IBRS bit remains always set which
* implicitly enables cross-thread protections. However, in legacy IBRS
* mode, the IBRS bit is set only on kernel entry and cleared on return
* to userspace. This disables the implicit cross-thread protection,
* so allow for STIBP to be selected in that case.
*/
if (!boot_cpu_has(X86_FEATURE_STIBP) ||
!smt_possible ||
spectre_v2_in_eibrs_mode(spectre_v2_enabled))
return;
/*
* At this point, an STIBP mode other than "off" has been set.
* If STIBP support is not being forced, check if STIBP always-on
* is preferred.
*/
if (mode != SPECTRE_V2_USER_STRICT &&
boot_cpu_has(X86_FEATURE_AMD_STIBP_ALWAYS_ON))
mode = SPECTRE_V2_USER_STRICT_PREFERRED;
if (retbleed_mitigation == RETBLEED_MITIGATION_UNRET ||
retbleed_mitigation == RETBLEED_MITIGATION_IBPB) {
if (mode != SPECTRE_V2_USER_STRICT &&
mode != SPECTRE_V2_USER_STRICT_PREFERRED)
pr_info("Selecting STIBP always-on mode to complement retbleed mitigation\n");
mode = SPECTRE_V2_USER_STRICT_PREFERRED;
}
spectre_v2_user_stibp = mode;
set_mode:
pr_info("%s\n", spectre_v2_user_strings[mode]);
}
static const char * const spectre_v2_strings[] = {
[SPECTRE_V2_NONE] = "Vulnerable",
[SPECTRE_V2_RETPOLINE] = "Mitigation: Retpolines",
[SPECTRE_V2_LFENCE] = "Mitigation: LFENCE",
[SPECTRE_V2_EIBRS] = "Mitigation: Enhanced / Automatic IBRS",
[SPECTRE_V2_EIBRS_LFENCE] = "Mitigation: Enhanced / Automatic IBRS + LFENCE",
[SPECTRE_V2_EIBRS_RETPOLINE] = "Mitigation: Enhanced / Automatic IBRS + Retpolines",
[SPECTRE_V2_IBRS] = "Mitigation: IBRS",
};
static const struct {
const char *option;
enum spectre_v2_mitigation_cmd cmd;
bool secure;
} mitigation_options[] __initconst = {
{ "off", SPECTRE_V2_CMD_NONE, false },
{ "on", SPECTRE_V2_CMD_FORCE, true },
{ "retpoline", SPECTRE_V2_CMD_RETPOLINE, false },
{ "retpoline,amd", SPECTRE_V2_CMD_RETPOLINE_LFENCE, false },
{ "retpoline,lfence", SPECTRE_V2_CMD_RETPOLINE_LFENCE, false },
{ "retpoline,generic", SPECTRE_V2_CMD_RETPOLINE_GENERIC, false },
{ "eibrs", SPECTRE_V2_CMD_EIBRS, false },
{ "eibrs,lfence", SPECTRE_V2_CMD_EIBRS_LFENCE, false },
{ "eibrs,retpoline", SPECTRE_V2_CMD_EIBRS_RETPOLINE, false },
{ "auto", SPECTRE_V2_CMD_AUTO, false },
{ "ibrs", SPECTRE_V2_CMD_IBRS, false },
};
static void __init spec_v2_print_cond(const char *reason, bool secure)
{
if (boot_cpu_has_bug(X86_BUG_SPECTRE_V2) != secure)
pr_info("%s selected on command line.\n", reason);
}
static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)
{
enum spectre_v2_mitigation_cmd cmd = SPECTRE_V2_CMD_AUTO;
char arg[20];
int ret, i;
if (cmdline_find_option_bool(boot_command_line, "nospectre_v2") ||
cpu_mitigations_off())
return SPECTRE_V2_CMD_NONE;
ret = cmdline_find_option(boot_command_line, "spectre_v2", arg, sizeof(arg));
if (ret < 0)
return SPECTRE_V2_CMD_AUTO;
for (i = 0; i < ARRAY_SIZE(mitigation_options); i++) {
if (!match_option(arg, ret, mitigation_options[i].option))
continue;
cmd = mitigation_options[i].cmd;
break;
}
if (i >= ARRAY_SIZE(mitigation_options)) {
pr_err("unknown option (%s). Switching to AUTO select\n", arg);
return SPECTRE_V2_CMD_AUTO;
}
if ((cmd == SPECTRE_V2_CMD_RETPOLINE ||
cmd == SPECTRE_V2_CMD_RETPOLINE_LFENCE ||
cmd == SPECTRE_V2_CMD_RETPOLINE_GENERIC ||
cmd == SPECTRE_V2_CMD_EIBRS_LFENCE ||
cmd == SPECTRE_V2_CMD_EIBRS_RETPOLINE) &&
!IS_ENABLED(CONFIG_RETPOLINE)) {
pr_err("%s selected but not compiled in. Switching to AUTO select\n",
mitigation_options[i].option);
return SPECTRE_V2_CMD_AUTO;
}
if ((cmd == SPECTRE_V2_CMD_EIBRS ||
cmd == SPECTRE_V2_CMD_EIBRS_LFENCE ||
cmd == SPECTRE_V2_CMD_EIBRS_RETPOLINE) &&
!boot_cpu_has(X86_FEATURE_IBRS_ENHANCED)) {
pr_err("%s selected but CPU doesn't have Enhanced or Automatic IBRS. Switching to AUTO select\n",
mitigation_options[i].option);
return SPECTRE_V2_CMD_AUTO;
}
if ((cmd == SPECTRE_V2_CMD_RETPOLINE_LFENCE ||
cmd == SPECTRE_V2_CMD_EIBRS_LFENCE) &&
!boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) {
pr_err("%s selected, but CPU doesn't have a serializing LFENCE. Switching to AUTO select\n",
mitigation_options[i].option);
return SPECTRE_V2_CMD_AUTO;
}
if (cmd == SPECTRE_V2_CMD_IBRS && !IS_ENABLED(CONFIG_CPU_IBRS_ENTRY)) {
pr_err("%s selected but not compiled in. Switching to AUTO select\n",
mitigation_options[i].option);
return SPECTRE_V2_CMD_AUTO;
}
if (cmd == SPECTRE_V2_CMD_IBRS && boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) {
pr_err("%s selected but not Intel CPU. Switching to AUTO select\n",
mitigation_options[i].option);
return SPECTRE_V2_CMD_AUTO;
}
if (cmd == SPECTRE_V2_CMD_IBRS && !boot_cpu_has(X86_FEATURE_IBRS)) {
pr_err("%s selected but CPU doesn't have IBRS. Switching to AUTO select\n",
mitigation_options[i].option);
return SPECTRE_V2_CMD_AUTO;
}
if (cmd == SPECTRE_V2_CMD_IBRS && cpu_feature_enabled(X86_FEATURE_XENPV)) {
pr_err("%s selected but running as XenPV guest. Switching to AUTO select\n",
mitigation_options[i].option);
return SPECTRE_V2_CMD_AUTO;
}
spec_v2_print_cond(mitigation_options[i].option,
mitigation_options[i].secure);
return cmd;
}
static enum spectre_v2_mitigation __init spectre_v2_select_retpoline(void)
{
if (!IS_ENABLED(CONFIG_RETPOLINE)) {
pr_err("Kernel not compiled with retpoline; no mitigation available!");
return SPECTRE_V2_NONE;
}
return SPECTRE_V2_RETPOLINE;
}
/* Disable in-kernel use of non-RSB RET predictors */
static void __init spec_ctrl_disable_kernel_rrsba(void)
{
u64 ia32_cap;
if (!boot_cpu_has(X86_FEATURE_RRSBA_CTRL))
return;
ia32_cap = x86_read_arch_cap_msr();
if (ia32_cap & ARCH_CAP_RRSBA) {
x86_spec_ctrl_base |= SPEC_CTRL_RRSBA_DIS_S;
update_spec_ctrl(x86_spec_ctrl_base);
}
}
static void __init spectre_v2_determine_rsb_fill_type_at_vmexit(enum spectre_v2_mitigation mode)
{
/*
* Similar to context switches, there are two types of RSB attacks
* after VM exit:
*
* 1) RSB underflow
*
* 2) Poisoned RSB entry
*
* When retpoline is enabled, both are mitigated by filling/clearing
* the RSB.
*
* When IBRS is enabled, while #1 would be mitigated by the IBRS branch
* prediction isolation protections, RSB still needs to be cleared
* because of #2. Note that SMEP provides no protection here, unlike
* user-space-poisoned RSB entries.
*
* eIBRS should protect against RSB poisoning, but if the EIBRS_PBRSB
* bug is present then a LITE version of RSB protection is required,
* just a single call needs to retire before a RET is executed.
*/
switch (mode) {
case SPECTRE_V2_NONE:
return;
case SPECTRE_V2_EIBRS_LFENCE:
case SPECTRE_V2_EIBRS:
if (boot_cpu_has_bug(X86_BUG_EIBRS_PBRSB)) {
setup_force_cpu_cap(X86_FEATURE_RSB_VMEXIT_LITE);
pr_info("Spectre v2 / PBRSB-eIBRS: Retire a single CALL on VMEXIT\n");
}
return;
case SPECTRE_V2_EIBRS_RETPOLINE:
case SPECTRE_V2_RETPOLINE:
case SPECTRE_V2_LFENCE:
case SPECTRE_V2_IBRS:
setup_force_cpu_cap(X86_FEATURE_RSB_VMEXIT);
pr_info("Spectre v2 / SpectreRSB : Filling RSB on VMEXIT\n");
return;
}
pr_warn_once("Unknown Spectre v2 mode, disabling RSB mitigation at VM exit");
dump_stack();
}
static void __init spectre_v2_select_mitigation(void)
{
enum spectre_v2_mitigation_cmd cmd = spectre_v2_parse_cmdline();
enum spectre_v2_mitigation mode = SPECTRE_V2_NONE;
/*
* If the CPU is not affected and the command line mode is NONE or AUTO
* then nothing to do.
*/
if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2) &&
(cmd == SPECTRE_V2_CMD_NONE || cmd == SPECTRE_V2_CMD_AUTO))
return;
switch (cmd) {
case SPECTRE_V2_CMD_NONE:
return;
case SPECTRE_V2_CMD_FORCE:
case SPECTRE_V2_CMD_AUTO:
if (boot_cpu_has(X86_FEATURE_IBRS_ENHANCED)) {
mode = SPECTRE_V2_EIBRS;
break;
}
if (IS_ENABLED(CONFIG_CPU_IBRS_ENTRY) &&
boot_cpu_has_bug(X86_BUG_RETBLEED) &&
retbleed_cmd != RETBLEED_CMD_OFF &&
retbleed_cmd != RETBLEED_CMD_STUFF &&
boot_cpu_has(X86_FEATURE_IBRS) &&
boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) {
mode = SPECTRE_V2_IBRS;
break;
}
mode = spectre_v2_select_retpoline();
break;
case SPECTRE_V2_CMD_RETPOLINE_LFENCE:
pr_err(SPECTRE_V2_LFENCE_MSG);
mode = SPECTRE_V2_LFENCE;
break;
case SPECTRE_V2_CMD_RETPOLINE_GENERIC:
mode = SPECTRE_V2_RETPOLINE;
break;
case SPECTRE_V2_CMD_RETPOLINE:
mode = spectre_v2_select_retpoline();
break;
case SPECTRE_V2_CMD_IBRS:
mode = SPECTRE_V2_IBRS;
break;
case SPECTRE_V2_CMD_EIBRS:
mode = SPECTRE_V2_EIBRS;
break;
case SPECTRE_V2_CMD_EIBRS_LFENCE:
mode = SPECTRE_V2_EIBRS_LFENCE;
break;
case SPECTRE_V2_CMD_EIBRS_RETPOLINE:
mode = SPECTRE_V2_EIBRS_RETPOLINE;
break;
}
if (mode == SPECTRE_V2_EIBRS && unprivileged_ebpf_enabled())
pr_err(SPECTRE_V2_EIBRS_EBPF_MSG);
if (spectre_v2_in_ibrs_mode(mode)) {
if (boot_cpu_has(X86_FEATURE_AUTOIBRS)) {
msr_set_bit(MSR_EFER, _EFER_AUTOIBRS);
} else {
x86_spec_ctrl_base |= SPEC_CTRL_IBRS;
update_spec_ctrl(x86_spec_ctrl_base);
}
}
switch (mode) {
case SPECTRE_V2_NONE:
case SPECTRE_V2_EIBRS:
break;
case SPECTRE_V2_IBRS:
setup_force_cpu_cap(X86_FEATURE_KERNEL_IBRS);
if (boot_cpu_has(X86_FEATURE_IBRS_ENHANCED))
pr_warn(SPECTRE_V2_IBRS_PERF_MSG);
break;
case SPECTRE_V2_LFENCE:
case SPECTRE_V2_EIBRS_LFENCE:
setup_force_cpu_cap(X86_FEATURE_RETPOLINE_LFENCE);
fallthrough;
case SPECTRE_V2_RETPOLINE:
case SPECTRE_V2_EIBRS_RETPOLINE:
setup_force_cpu_cap(X86_FEATURE_RETPOLINE);
break;
}
/*
* Disable alternate RSB predictions in kernel when indirect CALLs and
* JMPs gets protection against BHI and Intramode-BTI, but RET
* prediction from a non-RSB predictor is still a risk.
*/
if (mode == SPECTRE_V2_EIBRS_LFENCE ||
mode == SPECTRE_V2_EIBRS_RETPOLINE ||
mode == SPECTRE_V2_RETPOLINE)
spec_ctrl_disable_kernel_rrsba();
spectre_v2_enabled = mode;
pr_info("%s\n", spectre_v2_strings[mode]);
/*
* If Spectre v2 protection has been enabled, fill the RSB during a
* context switch. In general there are two types of RSB attacks
* across context switches, for which the CALLs/RETs may be unbalanced.
*
* 1) RSB underflow
*
* Some Intel parts have "bottomless RSB". When the RSB is empty,
* speculated return targets may come from the branch predictor,
* which could have a user-poisoned BTB or BHB entry.
*
* AMD has it even worse: *all* returns are speculated from the BTB,
* regardless of the state of the RSB.
*
* When IBRS or eIBRS is enabled, the "user -> kernel" attack
* scenario is mitigated by the IBRS branch prediction isolation
* properties, so the RSB buffer filling wouldn't be necessary to
* protect against this type of attack.
*
* The "user -> user" attack scenario is mitigated by RSB filling.
*
* 2) Poisoned RSB entry
*
* If the 'next' in-kernel return stack is shorter than 'prev',
* 'next' could be tricked into speculating with a user-poisoned RSB
* entry.
*
* The "user -> kernel" attack scenario is mitigated by SMEP and
* eIBRS.
*
* The "user -> user" scenario, also known as SpectreBHB, requires
* RSB clearing.
*
* So to mitigate all cases, unconditionally fill RSB on context
* switches.
*
* FIXME: Is this pointless for retbleed-affected AMD?
*/
setup_force_cpu_cap(X86_FEATURE_RSB_CTXSW);
pr_info("Spectre v2 / SpectreRSB mitigation: Filling RSB on context switch\n");
spectre_v2_determine_rsb_fill_type_at_vmexit(mode);
/*
* Retpoline protects the kernel, but doesn't protect firmware. IBRS
* and Enhanced IBRS protect firmware too, so enable IBRS around
* firmware calls only when IBRS / Enhanced / Automatic IBRS aren't
* otherwise enabled.
*
* Use "mode" to check Enhanced IBRS instead of boot_cpu_has(), because
* the user might select retpoline on the kernel command line and if
* the CPU supports Enhanced IBRS, kernel might un-intentionally not
* enable IBRS around firmware calls.
*/
if (boot_cpu_has_bug(X86_BUG_RETBLEED) &&
boot_cpu_has(X86_FEATURE_IBPB) &&
(boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
boot_cpu_data.x86_vendor == X86_VENDOR_HYGON)) {
if (retbleed_cmd != RETBLEED_CMD_IBPB) {
setup_force_cpu_cap(X86_FEATURE_USE_IBPB_FW);
pr_info("Enabling Speculation Barrier for firmware calls\n");
}
} else if (boot_cpu_has(X86_FEATURE_IBRS) && !spectre_v2_in_ibrs_mode(mode)) {
setup_force_cpu_cap(X86_FEATURE_USE_IBRS_FW);
pr_info("Enabling Restricted Speculation for firmware calls\n");
}
/* Set up IBPB and STIBP depending on the general spectre V2 command */
spectre_v2_cmd = cmd;
}
static void update_stibp_msr(void * __unused)
{
u64 val = spec_ctrl_current() | (x86_spec_ctrl_base & SPEC_CTRL_STIBP);
update_spec_ctrl(val);
}
/* Update x86_spec_ctrl_base in case SMT state changed. */
static void update_stibp_strict(void)
{
u64 mask = x86_spec_ctrl_base & ~SPEC_CTRL_STIBP;
if (sched_smt_active())
mask |= SPEC_CTRL_STIBP;
if (mask == x86_spec_ctrl_base)
return;
pr_info("Update user space SMT mitigation: STIBP %s\n",
mask & SPEC_CTRL_STIBP ? "always-on" : "off");
x86_spec_ctrl_base = mask;
on_each_cpu(update_stibp_msr, NULL, 1);
}
/* Update the static key controlling the evaluation of TIF_SPEC_IB */
static void update_indir_branch_cond(void)
{
if (sched_smt_active())
static_branch_enable(&switch_to_cond_stibp);
else
static_branch_disable(&switch_to_cond_stibp);
}
#undef pr_fmt
#define pr_fmt(fmt) fmt
/* Update the static key controlling the MDS CPU buffer clear in idle */
static void update_mds_branch_idle(void)
{
u64 ia32_cap = x86_read_arch_cap_msr();
/*
* Enable the idle clearing if SMT is active on CPUs which are
* affected only by MSBDS and not any other MDS variant.
*
* The other variants cannot be mitigated when SMT is enabled, so
* clearing the buffers on idle just to prevent the Store Buffer
* repartitioning leak would be a window dressing exercise.
*/
if (!boot_cpu_has_bug(X86_BUG_MSBDS_ONLY))
return;
if (sched_smt_active()) {
static_branch_enable(&mds_idle_clear);
} else if (mmio_mitigation == MMIO_MITIGATION_OFF ||
(ia32_cap & ARCH_CAP_FBSDP_NO)) {
static_branch_disable(&mds_idle_clear);
}
}
#define MDS_MSG_SMT "MDS CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/mds.html for more details.\n"
#define TAA_MSG_SMT "TAA CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/tsx_async_abort.html for more details.\n"
#define MMIO_MSG_SMT "MMIO Stale Data CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/processor_mmio_stale_data.html for more details.\n"
void cpu_bugs_smt_update(void)
{
mutex_lock(&spec_ctrl_mutex);
if (sched_smt_active() && unprivileged_ebpf_enabled() &&
spectre_v2_enabled == SPECTRE_V2_EIBRS_LFENCE)
pr_warn_once(SPECTRE_V2_EIBRS_LFENCE_EBPF_SMT_MSG);
switch (spectre_v2_user_stibp) {
case SPECTRE_V2_USER_NONE:
break;
case SPECTRE_V2_USER_STRICT:
case SPECTRE_V2_USER_STRICT_PREFERRED:
update_stibp_strict();
break;
case SPECTRE_V2_USER_PRCTL:
case SPECTRE_V2_USER_SECCOMP:
update_indir_branch_cond();
break;
}
switch (mds_mitigation) {
case MDS_MITIGATION_FULL:
case MDS_MITIGATION_VMWERV:
if (sched_smt_active() && !boot_cpu_has(X86_BUG_MSBDS_ONLY))
pr_warn_once(MDS_MSG_SMT);
update_mds_branch_idle();
break;
case MDS_MITIGATION_OFF:
break;
}
switch (taa_mitigation) {
case TAA_MITIGATION_VERW:
case TAA_MITIGATION_UCODE_NEEDED:
if (sched_smt_active())
pr_warn_once(TAA_MSG_SMT);
break;
case TAA_MITIGATION_TSX_DISABLED:
case TAA_MITIGATION_OFF:
break;
}
switch (mmio_mitigation) {
case MMIO_MITIGATION_VERW:
case MMIO_MITIGATION_UCODE_NEEDED:
if (sched_smt_active())
pr_warn_once(MMIO_MSG_SMT);
break;
case MMIO_MITIGATION_OFF:
break;
}
mutex_unlock(&spec_ctrl_mutex);
}
#undef pr_fmt
#define pr_fmt(fmt) "Speculative Store Bypass: " fmt
static enum ssb_mitigation ssb_mode __ro_after_init = SPEC_STORE_BYPASS_NONE;
/* The kernel command line selection */
enum ssb_mitigation_cmd {
SPEC_STORE_BYPASS_CMD_NONE,
SPEC_STORE_BYPASS_CMD_AUTO,
SPEC_STORE_BYPASS_CMD_ON,
SPEC_STORE_BYPASS_CMD_PRCTL,
SPEC_STORE_BYPASS_CMD_SECCOMP,
};
static const char * const ssb_strings[] = {
[SPEC_STORE_BYPASS_NONE] = "Vulnerable",
[SPEC_STORE_BYPASS_DISABLE] = "Mitigation: Speculative Store Bypass disabled",
[SPEC_STORE_BYPASS_PRCTL] = "Mitigation: Speculative Store Bypass disabled via prctl",
[SPEC_STORE_BYPASS_SECCOMP] = "Mitigation: Speculative Store Bypass disabled via prctl and seccomp",
};
static const struct {
const char *option;
enum ssb_mitigation_cmd cmd;
} ssb_mitigation_options[] __initconst = {
{ "auto", SPEC_STORE_BYPASS_CMD_AUTO }, /* Platform decides */
{ "on", SPEC_STORE_BYPASS_CMD_ON }, /* Disable Speculative Store Bypass */
{ "off", SPEC_STORE_BYPASS_CMD_NONE }, /* Don't touch Speculative Store Bypass */
{ "prctl", SPEC_STORE_BYPASS_CMD_PRCTL }, /* Disable Speculative Store Bypass via prctl */
{ "seccomp", SPEC_STORE_BYPASS_CMD_SECCOMP }, /* Disable Speculative Store Bypass via prctl and seccomp */
};
static enum ssb_mitigation_cmd __init ssb_parse_cmdline(void)
{
enum ssb_mitigation_cmd cmd = SPEC_STORE_BYPASS_CMD_AUTO;
char arg[20];
int ret, i;
if (cmdline_find_option_bool(boot_command_line, "nospec_store_bypass_disable") ||
cpu_mitigations_off()) {
return SPEC_STORE_BYPASS_CMD_NONE;
} else {
ret = cmdline_find_option(boot_command_line, "spec_store_bypass_disable",
arg, sizeof(arg));
if (ret < 0)
return SPEC_STORE_BYPASS_CMD_AUTO;
for (i = 0; i < ARRAY_SIZE(ssb_mitigation_options); i++) {
if (!match_option(arg, ret, ssb_mitigation_options[i].option))
continue;
cmd = ssb_mitigation_options[i].cmd;
break;
}
if (i >= ARRAY_SIZE(ssb_mitigation_options)) {
pr_err("unknown option (%s). Switching to AUTO select\n", arg);
return SPEC_STORE_BYPASS_CMD_AUTO;
}
}
return cmd;
}
static enum ssb_mitigation __init __ssb_select_mitigation(void)
{
enum ssb_mitigation mode = SPEC_STORE_BYPASS_NONE;
enum ssb_mitigation_cmd cmd;
if (!boot_cpu_has(X86_FEATURE_SSBD))
return mode;
cmd = ssb_parse_cmdline();
if (!boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS) &&
(cmd == SPEC_STORE_BYPASS_CMD_NONE ||
cmd == SPEC_STORE_BYPASS_CMD_AUTO))
return mode;
switch (cmd) {
case SPEC_STORE_BYPASS_CMD_SECCOMP:
/*
* Choose prctl+seccomp as the default mode if seccomp is
* enabled.
*/
if (IS_ENABLED(CONFIG_SECCOMP))
mode = SPEC_STORE_BYPASS_SECCOMP;
else
mode = SPEC_STORE_BYPASS_PRCTL;
break;
case SPEC_STORE_BYPASS_CMD_ON:
mode = SPEC_STORE_BYPASS_DISABLE;
break;
case SPEC_STORE_BYPASS_CMD_AUTO:
case SPEC_STORE_BYPASS_CMD_PRCTL:
mode = SPEC_STORE_BYPASS_PRCTL;
break;
case SPEC_STORE_BYPASS_CMD_NONE:
break;
}
/*
* We have three CPU feature flags that are in play here:
* - X86_BUG_SPEC_STORE_BYPASS - CPU is susceptible.
* - X86_FEATURE_SSBD - CPU is able to turn off speculative store bypass
* - X86_FEATURE_SPEC_STORE_BYPASS_DISABLE - engage the mitigation
*/
if (mode == SPEC_STORE_BYPASS_DISABLE) {
setup_force_cpu_cap(X86_FEATURE_SPEC_STORE_BYPASS_DISABLE);
/*
* Intel uses the SPEC CTRL MSR Bit(2) for this, while AMD may
* use a completely different MSR and bit dependent on family.
*/
if (!static_cpu_has(X86_FEATURE_SPEC_CTRL_SSBD) &&
!static_cpu_has(X86_FEATURE_AMD_SSBD)) {
x86_amd_ssb_disable();
} else {
x86_spec_ctrl_base |= SPEC_CTRL_SSBD;
update_spec_ctrl(x86_spec_ctrl_base);
}
}
return mode;
}
static void ssb_select_mitigation(void)
{
ssb_mode = __ssb_select_mitigation();
if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS))
pr_info("%s\n", ssb_strings[ssb_mode]);
}
#undef pr_fmt
#define pr_fmt(fmt) "Speculation prctl: " fmt
static void task_update_spec_tif(struct task_struct *tsk)
{
/* Force the update of the real TIF bits */
set_tsk_thread_flag(tsk, TIF_SPEC_FORCE_UPDATE);
/*
* Immediately update the speculation control MSRs for the current
* task, but for a non-current task delay setting the CPU
* mitigation until it is scheduled next.
*
* This can only happen for SECCOMP mitigation. For PRCTL it's
* always the current task.
*/
if (tsk == current)
speculation_ctrl_update_current();
}
static int l1d_flush_prctl_set(struct task_struct *task, unsigned long ctrl)
{
if (!static_branch_unlikely(&switch_mm_cond_l1d_flush))
return -EPERM;
switch (ctrl) {
case PR_SPEC_ENABLE:
set_ti_thread_flag(&task->thread_info, TIF_SPEC_L1D_FLUSH);
return 0;
case PR_SPEC_DISABLE:
clear_ti_thread_flag(&task->thread_info, TIF_SPEC_L1D_FLUSH);
return 0;
default:
return -ERANGE;
}
}
static int ssb_prctl_set(struct task_struct *task, unsigned long ctrl)
{
if (ssb_mode != SPEC_STORE_BYPASS_PRCTL &&
ssb_mode != SPEC_STORE_BYPASS_SECCOMP)
return -ENXIO;
switch (ctrl) {
case PR_SPEC_ENABLE:
/* If speculation is force disabled, enable is not allowed */
if (task_spec_ssb_force_disable(task))
return -EPERM;
task_clear_spec_ssb_disable(task);
task_clear_spec_ssb_noexec(task);
task_update_spec_tif(task);
break;
case PR_SPEC_DISABLE:
task_set_spec_ssb_disable(task);
task_clear_spec_ssb_noexec(task);
task_update_spec_tif(task);
break;
case PR_SPEC_FORCE_DISABLE:
task_set_spec_ssb_disable(task);
task_set_spec_ssb_force_disable(task);
task_clear_spec_ssb_noexec(task);
task_update_spec_tif(task);
break;
case PR_SPEC_DISABLE_NOEXEC:
if (task_spec_ssb_force_disable(task))
return -EPERM;
task_set_spec_ssb_disable(task);
task_set_spec_ssb_noexec(task);
task_update_spec_tif(task);
break;
default:
return -ERANGE;
}
return 0;
}
static bool is_spec_ib_user_controlled(void)
{
return spectre_v2_user_ibpb == SPECTRE_V2_USER_PRCTL ||
spectre_v2_user_ibpb == SPECTRE_V2_USER_SECCOMP ||
spectre_v2_user_stibp == SPECTRE_V2_USER_PRCTL ||
spectre_v2_user_stibp == SPECTRE_V2_USER_SECCOMP;
}
static int ib_prctl_set(struct task_struct *task, unsigned long ctrl)
{
switch (ctrl) {
case PR_SPEC_ENABLE:
if (spectre_v2_user_ibpb == SPECTRE_V2_USER_NONE &&
spectre_v2_user_stibp == SPECTRE_V2_USER_NONE)
return 0;
/*
* With strict mode for both IBPB and STIBP, the instruction
* code paths avoid checking this task flag and instead,
* unconditionally run the instruction. However, STIBP and IBPB
* are independent and either can be set to conditionally
* enabled regardless of the mode of the other.
*
* If either is set to conditional, allow the task flag to be
* updated, unless it was force-disabled by a previous prctl
* call. Currently, this is possible on an AMD CPU which has the
* feature X86_FEATURE_AMD_STIBP_ALWAYS_ON. In this case, if the
* kernel is booted with 'spectre_v2_user=seccomp', then
* spectre_v2_user_ibpb == SPECTRE_V2_USER_SECCOMP and
* spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT_PREFERRED.
*/
if (!is_spec_ib_user_controlled() ||
task_spec_ib_force_disable(task))
return -EPERM;
task_clear_spec_ib_disable(task);
task_update_spec_tif(task);
break;
case PR_SPEC_DISABLE:
case PR_SPEC_FORCE_DISABLE:
/*
* Indirect branch speculation is always allowed when
* mitigation is force disabled.
*/
if (spectre_v2_user_ibpb == SPECTRE_V2_USER_NONE &&
spectre_v2_user_stibp == SPECTRE_V2_USER_NONE)
return -EPERM;
if (!is_spec_ib_user_controlled())
return 0;
task_set_spec_ib_disable(task);
if (ctrl == PR_SPEC_FORCE_DISABLE)
task_set_spec_ib_force_disable(task);
task_update_spec_tif(task);
if (task == current)
indirect_branch_prediction_barrier();
break;
default:
return -ERANGE;
}
return 0;
}
int arch_prctl_spec_ctrl_set(struct task_struct *task, unsigned long which,
unsigned long ctrl)
{
switch (which) {
case PR_SPEC_STORE_BYPASS:
return ssb_prctl_set(task, ctrl);
case PR_SPEC_INDIRECT_BRANCH:
return ib_prctl_set(task, ctrl);
case PR_SPEC_L1D_FLUSH:
return l1d_flush_prctl_set(task, ctrl);
default:
return -ENODEV;
}
}
#ifdef CONFIG_SECCOMP
void arch_seccomp_spec_mitigate(struct task_struct *task)
{
if (ssb_mode == SPEC_STORE_BYPASS_SECCOMP)
ssb_prctl_set(task, PR_SPEC_FORCE_DISABLE);
if (spectre_v2_user_ibpb == SPECTRE_V2_USER_SECCOMP ||
spectre_v2_user_stibp == SPECTRE_V2_USER_SECCOMP)
ib_prctl_set(task, PR_SPEC_FORCE_DISABLE);
}
#endif
static int l1d_flush_prctl_get(struct task_struct *task)
{
if (!static_branch_unlikely(&switch_mm_cond_l1d_flush))
return PR_SPEC_FORCE_DISABLE;
if (test_ti_thread_flag(&task->thread_info, TIF_SPEC_L1D_FLUSH))
return PR_SPEC_PRCTL | PR_SPEC_ENABLE;
else
return PR_SPEC_PRCTL | PR_SPEC_DISABLE;
}
static int ssb_prctl_get(struct task_struct *task)
{
switch (ssb_mode) {
case SPEC_STORE_BYPASS_DISABLE:
return PR_SPEC_DISABLE;
case SPEC_STORE_BYPASS_SECCOMP:
case SPEC_STORE_BYPASS_PRCTL:
if (task_spec_ssb_force_disable(task))
return PR_SPEC_PRCTL | PR_SPEC_FORCE_DISABLE;
if (task_spec_ssb_noexec(task))
return PR_SPEC_PRCTL | PR_SPEC_DISABLE_NOEXEC;
if (task_spec_ssb_disable(task))
return PR_SPEC_PRCTL | PR_SPEC_DISABLE;
return PR_SPEC_PRCTL | PR_SPEC_ENABLE;
default:
if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS))
return PR_SPEC_ENABLE;
return PR_SPEC_NOT_AFFECTED;
}
}
static int ib_prctl_get(struct task_struct *task)
{
if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2))
return PR_SPEC_NOT_AFFECTED;
if (spectre_v2_user_ibpb == SPECTRE_V2_USER_NONE &&
spectre_v2_user_stibp == SPECTRE_V2_USER_NONE)
return PR_SPEC_ENABLE;
else if (is_spec_ib_user_controlled()) {
if (task_spec_ib_force_disable(task))
return PR_SPEC_PRCTL | PR_SPEC_FORCE_DISABLE;
if (task_spec_ib_disable(task))
return PR_SPEC_PRCTL | PR_SPEC_DISABLE;
return PR_SPEC_PRCTL | PR_SPEC_ENABLE;
} else if (spectre_v2_user_ibpb == SPECTRE_V2_USER_STRICT ||
spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT ||
spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT_PREFERRED)
return PR_SPEC_DISABLE;
else
return PR_SPEC_NOT_AFFECTED;
}
int arch_prctl_spec_ctrl_get(struct task_struct *task, unsigned long which)
{
switch (which) {
case PR_SPEC_STORE_BYPASS:
return ssb_prctl_get(task);
case PR_SPEC_INDIRECT_BRANCH:
return ib_prctl_get(task);
case PR_SPEC_L1D_FLUSH:
return l1d_flush_prctl_get(task);
default:
return -ENODEV;
}
}
void x86_spec_ctrl_setup_ap(void)
{
if (boot_cpu_has(X86_FEATURE_MSR_SPEC_CTRL))
update_spec_ctrl(x86_spec_ctrl_base);
if (ssb_mode == SPEC_STORE_BYPASS_DISABLE)
x86_amd_ssb_disable();
}
bool itlb_multihit_kvm_mitigation;
EXPORT_SYMBOL_GPL(itlb_multihit_kvm_mitigation);
#undef pr_fmt
#define pr_fmt(fmt) "L1TF: " fmt
/* Default mitigation for L1TF-affected CPUs */
enum l1tf_mitigations l1tf_mitigation __ro_after_init = L1TF_MITIGATION_FLUSH;
#if IS_ENABLED(CONFIG_KVM_INTEL)
EXPORT_SYMBOL_GPL(l1tf_mitigation);
#endif
enum vmx_l1d_flush_state l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_AUTO;
EXPORT_SYMBOL_GPL(l1tf_vmx_mitigation);
/*
* These CPUs all support 44bits physical address space internally in the
* cache but CPUID can report a smaller number of physical address bits.
*
* The L1TF mitigation uses the top most address bit for the inversion of
* non present PTEs. When the installed memory reaches into the top most
* address bit due to memory holes, which has been observed on machines
* which report 36bits physical address bits and have 32G RAM installed,
* then the mitigation range check in l1tf_select_mitigation() triggers.
* This is a false positive because the mitigation is still possible due to
* the fact that the cache uses 44bit internally. Use the cache bits
* instead of the reported physical bits and adjust them on the affected
* machines to 44bit if the reported bits are less than 44.
*/
static void override_cache_bits(struct cpuinfo_x86 *c)
{
if (c->x86 != 6)
return;
switch (c->x86_model) {
case INTEL_FAM6_NEHALEM:
case INTEL_FAM6_WESTMERE:
case INTEL_FAM6_SANDYBRIDGE:
case INTEL_FAM6_IVYBRIDGE:
case INTEL_FAM6_HASWELL:
case INTEL_FAM6_HASWELL_L:
case INTEL_FAM6_HASWELL_G:
case INTEL_FAM6_BROADWELL:
case INTEL_FAM6_BROADWELL_G:
case INTEL_FAM6_SKYLAKE_L:
case INTEL_FAM6_SKYLAKE:
case INTEL_FAM6_KABYLAKE_L:
case INTEL_FAM6_KABYLAKE:
if (c->x86_cache_bits < 44)
c->x86_cache_bits = 44;
break;
}
}
static void __init l1tf_select_mitigation(void)
{
u64 half_pa;
if (!boot_cpu_has_bug(X86_BUG_L1TF))
return;
if (cpu_mitigations_off())
l1tf_mitigation = L1TF_MITIGATION_OFF;
else if (cpu_mitigations_auto_nosmt())
l1tf_mitigation = L1TF_MITIGATION_FLUSH_NOSMT;
override_cache_bits(&boot_cpu_data);
switch (l1tf_mitigation) {
case L1TF_MITIGATION_OFF:
case L1TF_MITIGATION_FLUSH_NOWARN:
case L1TF_MITIGATION_FLUSH:
break;
case L1TF_MITIGATION_FLUSH_NOSMT:
case L1TF_MITIGATION_FULL:
cpu_smt_disable(false);
break;
case L1TF_MITIGATION_FULL_FORCE:
cpu_smt_disable(true);
break;
}
#if CONFIG_PGTABLE_LEVELS == 2
pr_warn("Kernel not compiled for PAE. No mitigation for L1TF\n");
return;
#endif
half_pa = (u64)l1tf_pfn_limit() << PAGE_SHIFT;
if (l1tf_mitigation != L1TF_MITIGATION_OFF &&
e820__mapped_any(half_pa, ULLONG_MAX - half_pa, E820_TYPE_RAM)) {
pr_warn("System has more than MAX_PA/2 memory. L1TF mitigation not effective.\n");
pr_info("You may make it effective by booting the kernel with mem=%llu parameter.\n",
half_pa);
pr_info("However, doing so will make a part of your RAM unusable.\n");
pr_info("Reading https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/l1tf.html might help you decide.\n");
return;
}
setup_force_cpu_cap(X86_FEATURE_L1TF_PTEINV);
}
static int __init l1tf_cmdline(char *str)
{
if (!boot_cpu_has_bug(X86_BUG_L1TF))
return 0;
if (!str)
return -EINVAL;
if (!strcmp(str, "off"))
l1tf_mitigation = L1TF_MITIGATION_OFF;
else if (!strcmp(str, "flush,nowarn"))
l1tf_mitigation = L1TF_MITIGATION_FLUSH_NOWARN;
else if (!strcmp(str, "flush"))
l1tf_mitigation = L1TF_MITIGATION_FLUSH;
else if (!strcmp(str, "flush,nosmt"))
l1tf_mitigation = L1TF_MITIGATION_FLUSH_NOSMT;
else if (!strcmp(str, "full"))
l1tf_mitigation = L1TF_MITIGATION_FULL;
else if (!strcmp(str, "full,force"))
l1tf_mitigation = L1TF_MITIGATION_FULL_FORCE;
return 0;
}
early_param("l1tf", l1tf_cmdline);
#undef pr_fmt
#define pr_fmt(fmt) fmt
#ifdef CONFIG_SYSFS
#define L1TF_DEFAULT_MSG "Mitigation: PTE Inversion"
#if IS_ENABLED(CONFIG_KVM_INTEL)
static const char * const l1tf_vmx_states[] = {
[VMENTER_L1D_FLUSH_AUTO] = "auto",
[VMENTER_L1D_FLUSH_NEVER] = "vulnerable",
[VMENTER_L1D_FLUSH_COND] = "conditional cache flushes",
[VMENTER_L1D_FLUSH_ALWAYS] = "cache flushes",
[VMENTER_L1D_FLUSH_EPT_DISABLED] = "EPT disabled",
[VMENTER_L1D_FLUSH_NOT_REQUIRED] = "flush not necessary"
};
static ssize_t l1tf_show_state(char *buf)
{
if (l1tf_vmx_mitigation == VMENTER_L1D_FLUSH_AUTO)
return sysfs_emit(buf, "%s\n", L1TF_DEFAULT_MSG);
if (l1tf_vmx_mitigation == VMENTER_L1D_FLUSH_EPT_DISABLED ||
(l1tf_vmx_mitigation == VMENTER_L1D_FLUSH_NEVER &&
sched_smt_active())) {
return sysfs_emit(buf, "%s; VMX: %s\n", L1TF_DEFAULT_MSG,
l1tf_vmx_states[l1tf_vmx_mitigation]);
}
return sysfs_emit(buf, "%s; VMX: %s, SMT %s\n", L1TF_DEFAULT_MSG,
l1tf_vmx_states[l1tf_vmx_mitigation],
sched_smt_active() ? "vulnerable" : "disabled");
}
static ssize_t itlb_multihit_show_state(char *buf)
{
if (!boot_cpu_has(X86_FEATURE_MSR_IA32_FEAT_CTL) ||
!boot_cpu_has(X86_FEATURE_VMX))
return sysfs_emit(buf, "KVM: Mitigation: VMX unsupported\n");
else if (!(cr4_read_shadow() & X86_CR4_VMXE))
return sysfs_emit(buf, "KVM: Mitigation: VMX disabled\n");
else if (itlb_multihit_kvm_mitigation)
return sysfs_emit(buf, "KVM: Mitigation: Split huge pages\n");
else
return sysfs_emit(buf, "KVM: Vulnerable\n");
}
#else
static ssize_t l1tf_show_state(char *buf)
{
return sysfs_emit(buf, "%s\n", L1TF_DEFAULT_MSG);
}
static ssize_t itlb_multihit_show_state(char *buf)
{
return sysfs_emit(buf, "Processor vulnerable\n");
}
#endif
static ssize_t mds_show_state(char *buf)
{
if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) {
return sysfs_emit(buf, "%s; SMT Host state unknown\n",
mds_strings[mds_mitigation]);
}
if (boot_cpu_has(X86_BUG_MSBDS_ONLY)) {
return sysfs_emit(buf, "%s; SMT %s\n", mds_strings[mds_mitigation],
(mds_mitigation == MDS_MITIGATION_OFF ? "vulnerable" :
sched_smt_active() ? "mitigated" : "disabled"));
}
return sysfs_emit(buf, "%s; SMT %s\n", mds_strings[mds_mitigation],
sched_smt_active() ? "vulnerable" : "disabled");
}
static ssize_t tsx_async_abort_show_state(char *buf)
{
if ((taa_mitigation == TAA_MITIGATION_TSX_DISABLED) ||
(taa_mitigation == TAA_MITIGATION_OFF))
return sysfs_emit(buf, "%s\n", taa_strings[taa_mitigation]);
if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) {
return sysfs_emit(buf, "%s; SMT Host state unknown\n",
taa_strings[taa_mitigation]);
}
return sysfs_emit(buf, "%s; SMT %s\n", taa_strings[taa_mitigation],
sched_smt_active() ? "vulnerable" : "disabled");
}
static ssize_t mmio_stale_data_show_state(char *buf)
{
if (boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN))
return sysfs_emit(buf, "Unknown: No mitigations\n");
if (mmio_mitigation == MMIO_MITIGATION_OFF)
return sysfs_emit(buf, "%s\n", mmio_strings[mmio_mitigation]);
if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) {
return sysfs_emit(buf, "%s; SMT Host state unknown\n",
mmio_strings[mmio_mitigation]);
}
return sysfs_emit(buf, "%s; SMT %s\n", mmio_strings[mmio_mitigation],
sched_smt_active() ? "vulnerable" : "disabled");
}
static char *stibp_state(void)
{
if (spectre_v2_in_eibrs_mode(spectre_v2_enabled))
return "";
switch (spectre_v2_user_stibp) {
case SPECTRE_V2_USER_NONE:
return ", STIBP: disabled";
case SPECTRE_V2_USER_STRICT:
return ", STIBP: forced";
case SPECTRE_V2_USER_STRICT_PREFERRED:
return ", STIBP: always-on";
case SPECTRE_V2_USER_PRCTL:
case SPECTRE_V2_USER_SECCOMP:
if (static_key_enabled(&switch_to_cond_stibp))
return ", STIBP: conditional";
}
return "";
}
static char *ibpb_state(void)
{
if (boot_cpu_has(X86_FEATURE_IBPB)) {
if (static_key_enabled(&switch_mm_always_ibpb))
return ", IBPB: always-on";
if (static_key_enabled(&switch_mm_cond_ibpb))
return ", IBPB: conditional";
return ", IBPB: disabled";
}
return "";
}
static char *pbrsb_eibrs_state(void)
{
if (boot_cpu_has_bug(X86_BUG_EIBRS_PBRSB)) {
if (boot_cpu_has(X86_FEATURE_RSB_VMEXIT_LITE) ||
boot_cpu_has(X86_FEATURE_RSB_VMEXIT))
return ", PBRSB-eIBRS: SW sequence";
else
return ", PBRSB-eIBRS: Vulnerable";
} else {
return ", PBRSB-eIBRS: Not affected";
}
}
static ssize_t spectre_v2_show_state(char *buf)
{
if (spectre_v2_enabled == SPECTRE_V2_LFENCE)
return sysfs_emit(buf, "Vulnerable: LFENCE\n");
if (spectre_v2_enabled == SPECTRE_V2_EIBRS && unprivileged_ebpf_enabled())
return sysfs_emit(buf, "Vulnerable: eIBRS with unprivileged eBPF\n");
if (sched_smt_active() && unprivileged_ebpf_enabled() &&
spectre_v2_enabled == SPECTRE_V2_EIBRS_LFENCE)
return sysfs_emit(buf, "Vulnerable: eIBRS+LFENCE with unprivileged eBPF and SMT\n");
return sysfs_emit(buf, "%s%s%s%s%s%s%s\n",
spectre_v2_strings[spectre_v2_enabled],
ibpb_state(),
boot_cpu_has(X86_FEATURE_USE_IBRS_FW) ? ", IBRS_FW" : "",
stibp_state(),
boot_cpu_has(X86_FEATURE_RSB_CTXSW) ? ", RSB filling" : "",
pbrsb_eibrs_state(),
spectre_v2_module_string());
}
static ssize_t srbds_show_state(char *buf)
{
return sysfs_emit(buf, "%s\n", srbds_strings[srbds_mitigation]);
}
static ssize_t retbleed_show_state(char *buf)
{
if (retbleed_mitigation == RETBLEED_MITIGATION_UNRET ||
retbleed_mitigation == RETBLEED_MITIGATION_IBPB) {
if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD &&
boot_cpu_data.x86_vendor != X86_VENDOR_HYGON)
return sysfs_emit(buf, "Vulnerable: untrained return thunk / IBPB on non-AMD based uarch\n");
return sysfs_emit(buf, "%s; SMT %s\n", retbleed_strings[retbleed_mitigation],
!sched_smt_active() ? "disabled" :
spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT ||
spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT_PREFERRED ?
"enabled with STIBP protection" : "vulnerable");
}
return sysfs_emit(buf, "%s\n", retbleed_strings[retbleed_mitigation]);
}
static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr,
char *buf, unsigned int bug)
{
if (!boot_cpu_has_bug(bug))
return sysfs_emit(buf, "Not affected\n");
switch (bug) {
case X86_BUG_CPU_MELTDOWN:
if (boot_cpu_has(X86_FEATURE_PTI))
return sysfs_emit(buf, "Mitigation: PTI\n");
if (hypervisor_is_type(X86_HYPER_XEN_PV))
return sysfs_emit(buf, "Unknown (XEN PV detected, hypervisor mitigation required)\n");
break;
case X86_BUG_SPECTRE_V1:
return sysfs_emit(buf, "%s\n", spectre_v1_strings[spectre_v1_mitigation]);
case X86_BUG_SPECTRE_V2:
return spectre_v2_show_state(buf);
case X86_BUG_SPEC_STORE_BYPASS:
return sysfs_emit(buf, "%s\n", ssb_strings[ssb_mode]);
case X86_BUG_L1TF:
if (boot_cpu_has(X86_FEATURE_L1TF_PTEINV))
return l1tf_show_state(buf);
break;
case X86_BUG_MDS:
return mds_show_state(buf);
case X86_BUG_TAA:
return tsx_async_abort_show_state(buf);
case X86_BUG_ITLB_MULTIHIT:
return itlb_multihit_show_state(buf);
case X86_BUG_SRBDS:
return srbds_show_state(buf);
case X86_BUG_MMIO_STALE_DATA:
case X86_BUG_MMIO_UNKNOWN:
return mmio_stale_data_show_state(buf);
case X86_BUG_RETBLEED:
return retbleed_show_state(buf);
default:
break;
}
return sysfs_emit(buf, "Vulnerable\n");
}
ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, char *buf)
{
return cpu_show_common(dev, attr, buf, X86_BUG_CPU_MELTDOWN);
}
ssize_t cpu_show_spectre_v1(struct device *dev, struct device_attribute *attr, char *buf)
{
return cpu_show_common(dev, attr, buf, X86_BUG_SPECTRE_V1);
}
ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr, char *buf)
{
return cpu_show_common(dev, attr, buf, X86_BUG_SPECTRE_V2);
}
ssize_t cpu_show_spec_store_bypass(struct device *dev, struct device_attribute *attr, char *buf)
{
return cpu_show_common(dev, attr, buf, X86_BUG_SPEC_STORE_BYPASS);
}
ssize_t cpu_show_l1tf(struct device *dev, struct device_attribute *attr, char *buf)
{
return cpu_show_common(dev, attr, buf, X86_BUG_L1TF);
}
ssize_t cpu_show_mds(struct device *dev, struct device_attribute *attr, char *buf)
{
return cpu_show_common(dev, attr, buf, X86_BUG_MDS);
}
ssize_t cpu_show_tsx_async_abort(struct device *dev, struct device_attribute *attr, char *buf)
{
return cpu_show_common(dev, attr, buf, X86_BUG_TAA);
}
ssize_t cpu_show_itlb_multihit(struct device *dev, struct device_attribute *attr, char *buf)
{
return cpu_show_common(dev, attr, buf, X86_BUG_ITLB_MULTIHIT);
}
ssize_t cpu_show_srbds(struct device *dev, struct device_attribute *attr, char *buf)
{
return cpu_show_common(dev, attr, buf, X86_BUG_SRBDS);
}
ssize_t cpu_show_mmio_stale_data(struct device *dev, struct device_attribute *attr, char *buf)
{
if (boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN))
return cpu_show_common(dev, attr, buf, X86_BUG_MMIO_UNKNOWN);
else
return cpu_show_common(dev, attr, buf, X86_BUG_MMIO_STALE_DATA);
}
ssize_t cpu_show_retbleed(struct device *dev, struct device_attribute *attr, char *buf)
{
return cpu_show_common(dev, attr, buf, X86_BUG_RETBLEED);
}
#endif
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