diff options
| -rw-r--r-- | Documentation/ABI/testing/sysfs-devices-system-cpu | 1 | ||||
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 11 | ||||
| -rw-r--r-- | arch/x86/Kconfig | 9 | ||||
| -rw-r--r-- | arch/x86/kernel/cpu/bugs.c | 90 | ||||
| -rw-r--r-- | drivers/base/cpu.c | 3 | ||||
| -rw-r--r-- | include/linux/cpu.h | 1 |
6 files changed, 115 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu index ab8cd337f43a..8aed6d94c4cd 100644 --- a/Documentation/ABI/testing/sysfs-devices-system-cpu +++ b/Documentation/ABI/testing/sysfs-devices-system-cpu @@ -586,6 +586,7 @@ What: /sys/devices/system/cpu/vulnerabilities /sys/devices/system/cpu/vulnerabilities/srbds /sys/devices/system/cpu/vulnerabilities/tsa /sys/devices/system/cpu/vulnerabilities/tsx_async_abort + /sys/devices/system/cpu/vulnerabilities/vmscape Date: January 2018 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> Description: Information about CPU vulnerabilities diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 747a55abf494..5a7a83c411e9 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3829,6 +3829,7 @@ srbds=off [X86,INTEL] ssbd=force-off [ARM64] tsx_async_abort=off [X86] + vmscape=off [X86] Exceptions: This does not have any effect on @@ -8041,6 +8042,16 @@ vmpoff= [KNL,S390] Perform z/VM CP command after power off. Format: <command> + vmscape= [X86] Controls mitigation for VMscape attacks. + VMscape attacks can leak information from a userspace + hypervisor to a guest via speculative side-channels. + + off - disable the mitigation + ibpb - use Indirect Branch Prediction Barrier + (IBPB) mitigation (default) + force - force vulnerability detection even on + unaffected processors + vsyscall= [X86-64,EARLY] Controls the behavior of vsyscalls (i.e. calls to fixed addresses of 0xffffffffff600x00 from legacy diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 58d890fe2100..52c8910ba2ef 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2701,6 +2701,15 @@ config MITIGATION_TSA security vulnerability on AMD CPUs which can lead to forwarding of invalid info to subsequent instructions and thus can affect their timing and thereby cause a leakage. + +config MITIGATION_VMSCAPE + bool "Mitigate VMSCAPE" + depends on KVM + default y + help + Enable mitigation for VMSCAPE attacks. VMSCAPE is a hardware security + vulnerability on Intel and AMD CPUs that may allow a guest to do + Spectre v2 style attacks on userspace hypervisor. endif config ARCH_HAS_ADD_PAGES diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 410f8df8b77a..c81024dfc4c8 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -96,6 +96,9 @@ static void __init its_update_mitigation(void); static void __init its_apply_mitigation(void); static void __init tsa_select_mitigation(void); static void __init tsa_apply_mitigation(void); +static void __init vmscape_select_mitigation(void); +static void __init vmscape_update_mitigation(void); +static void __init vmscape_apply_mitigation(void); /* The base value of the SPEC_CTRL MSR without task-specific bits set */ u64 x86_spec_ctrl_base; @@ -270,6 +273,7 @@ void __init cpu_select_mitigations(void) its_select_mitigation(); bhi_select_mitigation(); tsa_select_mitigation(); + vmscape_select_mitigation(); /* * After mitigations are selected, some may need to update their @@ -301,6 +305,7 @@ void __init cpu_select_mitigations(void) bhi_update_mitigation(); /* srso_update_mitigation() depends on retbleed_update_mitigation(). */ srso_update_mitigation(); + vmscape_update_mitigation(); spectre_v1_apply_mitigation(); spectre_v2_apply_mitigation(); @@ -318,6 +323,7 @@ void __init cpu_select_mitigations(void) its_apply_mitigation(); bhi_apply_mitigation(); tsa_apply_mitigation(); + vmscape_apply_mitigation(); } /* @@ -3323,6 +3329,77 @@ static void __init srso_apply_mitigation(void) } #undef pr_fmt +#define pr_fmt(fmt) "VMSCAPE: " fmt + +enum vmscape_mitigations { + VMSCAPE_MITIGATION_NONE, + VMSCAPE_MITIGATION_AUTO, + VMSCAPE_MITIGATION_IBPB_EXIT_TO_USER, + VMSCAPE_MITIGATION_IBPB_ON_VMEXIT, +}; + +static const char * const vmscape_strings[] = { + [VMSCAPE_MITIGATION_NONE] = "Vulnerable", + /* [VMSCAPE_MITIGATION_AUTO] */ + [VMSCAPE_MITIGATION_IBPB_EXIT_TO_USER] = "Mitigation: IBPB before exit to userspace", + [VMSCAPE_MITIGATION_IBPB_ON_VMEXIT] = "Mitigation: IBPB on VMEXIT", +}; + +static enum vmscape_mitigations vmscape_mitigation __ro_after_init = + IS_ENABLED(CONFIG_MITIGATION_VMSCAPE) ? VMSCAPE_MITIGATION_AUTO : VMSCAPE_MITIGATION_NONE; + +static int __init vmscape_parse_cmdline(char *str) +{ + if (!str) + return -EINVAL; + + if (!strcmp(str, "off")) { + vmscape_mitigation = VMSCAPE_MITIGATION_NONE; + } else if (!strcmp(str, "ibpb")) { + vmscape_mitigation = VMSCAPE_MITIGATION_IBPB_EXIT_TO_USER; + } else if (!strcmp(str, "force")) { + setup_force_cpu_bug(X86_BUG_VMSCAPE); + vmscape_mitigation = VMSCAPE_MITIGATION_AUTO; + } else { + pr_err("Ignoring unknown vmscape=%s option.\n", str); + } + + return 0; +} +early_param("vmscape", vmscape_parse_cmdline); + +static void __init vmscape_select_mitigation(void) +{ + if (cpu_mitigations_off() || + !boot_cpu_has_bug(X86_BUG_VMSCAPE) || + !boot_cpu_has(X86_FEATURE_IBPB)) { + vmscape_mitigation = VMSCAPE_MITIGATION_NONE; + return; + } + + if (vmscape_mitigation == VMSCAPE_MITIGATION_AUTO) + vmscape_mitigation = VMSCAPE_MITIGATION_IBPB_EXIT_TO_USER; +} + +static void __init vmscape_update_mitigation(void) +{ + if (!boot_cpu_has_bug(X86_BUG_VMSCAPE)) + return; + + if (retbleed_mitigation == RETBLEED_MITIGATION_IBPB || + srso_mitigation == SRSO_MITIGATION_IBPB_ON_VMEXIT) + vmscape_mitigation = VMSCAPE_MITIGATION_IBPB_ON_VMEXIT; + + pr_info("%s\n", vmscape_strings[vmscape_mitigation]); +} + +static void __init vmscape_apply_mitigation(void) +{ + if (vmscape_mitigation == VMSCAPE_MITIGATION_IBPB_EXIT_TO_USER) + setup_force_cpu_cap(X86_FEATURE_IBPB_EXIT_TO_USER); +} + +#undef pr_fmt #define pr_fmt(fmt) fmt #ifdef CONFIG_SYSFS @@ -3570,6 +3647,11 @@ static ssize_t tsa_show_state(char *buf) return sysfs_emit(buf, "%s\n", tsa_strings[tsa_mitigation]); } +static ssize_t vmscape_show_state(char *buf) +{ + return sysfs_emit(buf, "%s\n", vmscape_strings[vmscape_mitigation]); +} + static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr, char *buf, unsigned int bug) { @@ -3636,6 +3718,9 @@ static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr case X86_BUG_TSA: return tsa_show_state(buf); + case X86_BUG_VMSCAPE: + return vmscape_show_state(buf); + default: break; } @@ -3727,6 +3812,11 @@ ssize_t cpu_show_tsa(struct device *dev, struct device_attribute *attr, char *bu { return cpu_show_common(dev, attr, buf, X86_BUG_TSA); } + +ssize_t cpu_show_vmscape(struct device *dev, struct device_attribute *attr, char *buf) +{ + return cpu_show_common(dev, attr, buf, X86_BUG_VMSCAPE); +} #endif void __warn_thunk(void) diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c index efc575a00edd..008da0354fba 100644 --- a/drivers/base/cpu.c +++ b/drivers/base/cpu.c @@ -603,6 +603,7 @@ CPU_SHOW_VULN_FALLBACK(ghostwrite); CPU_SHOW_VULN_FALLBACK(old_microcode); CPU_SHOW_VULN_FALLBACK(indirect_target_selection); CPU_SHOW_VULN_FALLBACK(tsa); +CPU_SHOW_VULN_FALLBACK(vmscape); static DEVICE_ATTR(meltdown, 0444, cpu_show_meltdown, NULL); static DEVICE_ATTR(spectre_v1, 0444, cpu_show_spectre_v1, NULL); @@ -622,6 +623,7 @@ static DEVICE_ATTR(ghostwrite, 0444, cpu_show_ghostwrite, NULL); static DEVICE_ATTR(old_microcode, 0444, cpu_show_old_microcode, NULL); static DEVICE_ATTR(indirect_target_selection, 0444, cpu_show_indirect_target_selection, NULL); static DEVICE_ATTR(tsa, 0444, cpu_show_tsa, NULL); +static DEVICE_ATTR(vmscape, 0444, cpu_show_vmscape, NULL); static struct attribute *cpu_root_vulnerabilities_attrs[] = { &dev_attr_meltdown.attr, @@ -642,6 +644,7 @@ static struct attribute *cpu_root_vulnerabilities_attrs[] = { &dev_attr_old_microcode.attr, &dev_attr_indirect_target_selection.attr, &dev_attr_tsa.attr, + &dev_attr_vmscape.attr, NULL }; diff --git a/include/linux/cpu.h b/include/linux/cpu.h index b91b993f58ee..487b3bf2e1ea 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -83,6 +83,7 @@ extern ssize_t cpu_show_old_microcode(struct device *dev, extern ssize_t cpu_show_indirect_target_selection(struct device *dev, struct device_attribute *attr, char *buf); extern ssize_t cpu_show_tsa(struct device *dev, struct device_attribute *attr, char *buf); +extern ssize_t cpu_show_vmscape(struct device *dev, struct device_attribute *attr, char *buf); extern __printf(4, 5) struct device *cpu_device_create(struct device *parent, void *drvdata, |