sysfs/cpu: Add vulnerability folder

CVE-2017-5715 (Spectre v2 retpoline)

commit 87590ce6e373d1a5401f6539f0c59ef92dd924a9 upstream.

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 <tglx@linutronix.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linuxfoundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Link: https://lkml.kernel.org/r/20180107214913.096657732@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(backported from commit 73492b6860129bc3b87b1730486940d0850bfb23)
Signed-off-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
index 16501334b99fe88544534274c837b822a03d0d70..8e3f4fccd33679308fe8b811a6746a8f07936cb2 100644 (file)
--- a/Documentation/ABI/testing/sysfs-devices-system-cpu
+++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
@@ -340,3 +340,19 @@ Description:       POWERNV CPUFreq driver's frequency throttle stats directory and
                'policyX/throttle_stats' directory and all the attributes are same as
                the /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats directory and
                attributes which give the frequency throttle information of the chip.
+
+What:          /sys/devices/system/cpu/vulnerabilities
+               /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 <linux-kernel@vger.kernel.org>
+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. Possible output values:
+
+               "Not affected"    CPU is not affected by the vulnerability
+               "Vulnerable"      CPU is affected and no mitigation in effect
+               "Mitigation: $M"  CPU is affetcted and mitigation $M is in effect

diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
index 98504ec99c7d9e52ce44c317504fab2d585ce476..59992788966c8f6855444582e37461b7db688d68 100644 (file)
--- a/drivers/base/Kconfig
+++ b/drivers/base/Kconfig
@@ -223,6 +223,9 @@ config GENERIC_CPU_DEVICES
 config GENERIC_CPU_AUTOPROBE
        bool
 
+config GENERIC_CPU_VULNERABILITIES
+       bool
+
 config SOC_BUS
        bool
 

diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 91bbb1959d8d0a831b7a7f0dc6472f2e5d4937b1..3db71afbba93c54d807438c5ea2678be6428a05d 100644 (file)
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -498,10 +498,58 @@ static void __init cpu_dev_register_generic(void)
 #endif
 }
 
+#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();
 }

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 3ea9aae2387d7f79b8d0a14891a8a10b4412d254..7e04bcd9af8ef8be9781a9a1b403d09fb603305f 100644 (file)
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -40,6 +40,13 @@ extern void cpu_remove_dev_attr(struct device_attribute *attr);
 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,