sysfs/cpu: Implement generic vulnerabilites directory

As the meltdown/spectre problem affects several CPU architectures, it makes sense to have common way to express whether a system is affected by a particular vulnerability or not. If affected the way to express the mitigation should be common as well.

Create /sys/devices/system/cpu/vulnerabilities folder and files for meltdown, spectre_v1 and spectre_v2.

Allow architectures to override the show function.

Signed-off-by Thomas Gleixner <[email protected]>

---
 Documentation/ABI/testing/sysfs-devices-system-cpu |   16 +++++++
 drivers/base/Kconfig                               |    3 +
 drivers/base/cpu.c                                 |   48 +++++++++++++++++++++
 include/linux/cpu.h                                |    7 +++
 4 files changed, 74 insertions(+)

Documentation/ABI/testing/sysfs-devices-system-cpu +48 -0

+#ifdef CONFIG_GENERIC_CPU_VULNERABILITIES
+
+ssize_t __weak cpu_show_meltdown(struct device *dev,
+				 struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "Not affected\n");
+}
+
+ssize_t __weak cpu_show_spectre_v1(struct device *dev,
+				   struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "Not affected\n");
+}
+
+ssize_t __weak cpu_show_spectre_v2(struct device *dev,
+				   struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "Not affected\n");
+}
+
+static DEVICE_ATTR(meltdown, 0444, cpu_show_meltdown, NULL);
+static DEVICE_ATTR(spectre_v1, 0444, cpu_show_spectre_v1, NULL);
+static DEVICE_ATTR(spectre_v2, 0444, cpu_show_spectre_v2, NULL);
+
+static struct attribute *cpu_root_vulnerabilities_attrs[] = {
+	&dev_attr_meltdown.attr,
+	&dev_attr_spectre_v1.attr,
+	&dev_attr_spectre_v2.attr,
+	NULL
+};
+
+static const struct attribute_group cpu_root_vulnerabilities_group = {
+	.name  = "vulnerabilities",
+	.attrs = cpu_root_vulnerabilities_attrs,
+};
+
+static void __init cpu_register_vulnerabilities(void)
+{
+	if (sysfs_create_group(&cpu_subsys.dev_root->kobj,
+			       &cpu_root_vulnerabilities_group))
+		pr_err("Unable to register CPU vulnerabilities\n");
+}
+
+#else
+static inline void cpu_register_vulnerabilities(void) { }
+#endif
+
 void __init cpu_dev_init(void)
 {
 	if (subsys_system_register(&cpu_subsys, cpu_root_attr_groups))
 		panic("Failed to register CPU subsystem");
 
 	cpu_dev_register_generic();
+	cpu_register_vulnerabilities();
 }

include/linux/cpu.h +7 -0

@@ -47,6 +47,13 @@ extern void cpu_remove_dev_attr(struct d
 extern int cpu_add_dev_attr_group(struct attribute_group *attrs);
 extern void cpu_remove_dev_attr_group(struct attribute_group *attrs);
 
+extern ssize_t cpu_show_meltdown(struct device *dev,
+				 struct device_attribute *attr, char *buf);
+extern ssize_t cpu_show_spectre_v1(struct device *dev,
+				   struct device_attribute *attr, char *buf);
+extern ssize_t cpu_show_spectre_v2(struct device *dev,
+				   struct device_attribute *attr, char *buf);
+
 extern __printf(4, 5)
 struct device *cpu_device_create(struct device *parent, void *drvdata,
 				 const struct attribute_group **groups,

As the meltdown/spectre problem affects several CPU architectures, it makes sense to have common way to express whether a system is affected by a particular vulnerability or not. If affected the way to express the mitigation should be common as well.

Create /sys/devices/system/cpu/vulnerabilities folder and files for meltdown, spectre_v1 and spectre_v2.

Allow architectures to override the show function.

Signed-off-by Thomas Gleixner <[email protected]>

As the meltdown/spectre problem affects several CPU architectures, it makes sense to have common way to express whether a system is affected by a particular vulnerability or not. If affected the way to express the mitigation should be common as well.

Create /sys/devices/system/cpu/vulnerabilities folder and files for meltdown, spectre_v1 and spectre_v2.

Allow architectures to override the show function.

Signed-off-by Thomas Gleixner <[email protected]>

---
 Documentation/ABI/testing/sysfs-devices-system-cpu |   16 +++++++
 drivers/base/Kconfig                               |    3 +
 drivers/base/cpu.c                                 |   48 +++++++++++++++++++++
 include/linux/cpu.h                                |    7 +++
 4 files changed, 74 insertions(+)

Documentation/ABI/testing/sysfs-devices-system-cpu +2 -0

@@ -373,3 +373,19 @@ Contact:	Linux kernel mailing list <linu
 Description:	information about CPUs heterogeneity.
 
 		cpu_capacity: capacity of cpu#.
+
+What:		/sys/devices/system/cpu/vulnerabilities

Quoted 26 lines · Thomas Gleixner

As the meltdown/spectre problem affects several CPU architectures, it makes sense to have common way to express whether a system is affected by a particular vulnerability or not. If affected the way to express the mitigation should be common as well.

Create /sys/devices/system/cpu/vulnerabilities folder and files for meltdown, spectre_v1 and spectre_v2.

Allow architectures to override the show function.

Signed-off-by Thomas Gleixner <[email protected]>

---
 Documentation/ABI/testing/sysfs-devices-system-cpu |   16 +++++++
 drivers/base/Kconfig                               |    3 +
 drivers/base/cpu.c                                 |   48 +++++++++++++++++++++
 include/linux/cpu.h                                |    7 +++
 4 files changed, 74 insertions(+)

Documentation/ABI/testing/sysfs-devices-system-cpu +2 -0

@@ -373,3 +373,19 @@ Contact:	Linux kernel mailing list <linu
 Description:	information about CPUs heterogeneity.
 
 		cpu_capacity: capacity of cpu#.
+
+What:		/sys/devices/system/cpu/vulnerabilities

Documentation/ABI/testing/sysfs-devices-system-cpu Contact: Linux kernel mailing list <linu · line 387

Quoted 10 lines

Documentation/ABI/testing/sysfs-devices-system-cpu +10 -0

+		/sys/devices/system/cpu/vulnerabilities/meltdown
+		/sys/devices/system/cpu/vulnerabilities/spectre_v1
+		/sys/devices/system/cpu/vulnerabilities/spectre_v2
+Date:		Januar 2018
+Contact:	Linux kernel mailing list <[email protected]>
+Description:	Information about CPU vulnerabilities
+
+		The files are named after the code names of CPU
+		vulnerabilities. The output of those files reflects the
+		state of the CPUs in the system.

Currently, your code sets X86_BUG_SPECTRE_V[12] unconditionally on x86 CPUs. However, to my understanding some CPUs which do not execute code out-of-order aren't affected. As it is better to err on the safe side for now, what about adding a disclaimer at the end of this sentence, such as:

", but may contain false positives"

From 578b411c8dcb1435dd1f94a6cd062f4eedb70fb5 Mon Sep 17 00:00:00 2001

Hello,

Review

Quoted 3 lines · Thomas Gleixner

(quoted diff) +3 -0

+static DEVICE_ATTR(meltdown, 0444, cpu_show_meltdown, NULL);
+static DEVICE_ATTR(spectre_v1, 0444, cpu_show_spectre_v1, NULL);
+static DEVICE_ATTR(spectre_v2, 0444, cpu_show_spectre_v2, NULL);

This sysfs feature implemented as above is weakening kernel security, it should be 0400 above.

drivers/base/cpu.c +9 -0

+#ifdef CONFIG_GENERIC_CPU_VULNERABILITIES
+
+ssize_t __weak cpu_show_meltdown(struct device *dev,
+				 struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "Not affected\n");
+}
+
+ssize_t __weak cpu_show_spectre_v1(struct device *dev,

Implement the CPU vulnerabilty show functions for meltdown, spectre_v1 and spectre_v2.

Signed-off-by Thomas Gleixner <[email protected]>

---
 arch/x86/Kconfig           |    1 +
 arch/x86/kernel/cpu/bugs.c |   29 +++++++++++++++++++++++++++++
 2 files changed, 30 insertions(+)

arch/x86/Kconfig +1 -0

@@ -89,6 +89,7 @@ config X86
 	select GENERIC_CLOCKEVENTS_MIN_ADJUST
 	select GENERIC_CMOS_UPDATE
 	select GENERIC_CPU_AUTOPROBE
+	select GENERIC_CPU_VULNERABILITIES
 	select GENERIC_EARLY_IOREMAP
 	select GENERIC_FIND_FIRST_BIT
 	select GENERIC_IOMAP

arch/x86/kernel/cpu/bugs.c +29 -0

@@ -10,6 +10,7 @@
  */
 #include <linux/init.h>
 #include <linux/utsname.h>
+#include <linux/cpu.h>
 #include <asm/bugs.h>
 #include <asm/processor.h>
 #include <asm/processor-flags.h>

@@ -60,3 +61,31 @@ void __init check_bugs(void)
 		set_memory_4k((unsigned long)__va(0), 1);
 #endif
 }
+
+#ifdef CONFIG_SYSFS
+ssize_t cpu_show_meltdown(struct device *dev,
+			  struct device_attribute *attr, char *buf)
+{
+	if (!boot_cpu_has_bug(X86_BUG_CPU_MELTDOWN))
+		return sprintf(buf, "Not affected\n");
+	if (boot_cpu_has(X86_FEATURE_PTI))
+		return sprintf(buf, "Mitigation: PTI\n");
+	return sprintf(buf, "Vulnerable\n");
+}
+
+ssize_t cpu_show_spectre_v1(struct device *dev,
+			    struct device_attribute *attr, char *buf)
+{
+	if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V1))
+		return sprintf(buf, "Not affected\n");
+	return sprintf(buf, "Vulnerable\n");
+}
+
+ssize_t cpu_show_spectre_v2(struct device *dev,
+			    struct device_attribute *attr, char *buf)
+{
+	if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2))
+		return sprintf(buf, "Not affected\n");
+	return sprintf(buf, "Vulnerable\n");
+}
+#endif

Implement the CPU vulnerabilty show functions for meltdown, spectre_v1 and spectre_v2.

Signed-off-by Thomas Gleixner <[email protected]>

---
 arch/x86/Kconfig           |    1 +
 arch/x86/kernel/cpu/bugs.c |   29 +++++++++++++++++++++++++++++
 2 files changed, 30 insertions(+)