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authorSeunghun Han <kkamagui@gmail.com>2018-03-06 15:21:43 +0100
committerThomas Gleixner <tglx@linutronix.de>2018-03-08 15:36:27 +0100
commitb3b7c4795ccab5be71f080774c45bbbcc75c2aaf (patch)
treee17563a8e944b6bc4c33bd587aa13383d6038c05 /arch
parentfa94d0c6e0f3431523f5701084d799c77c7d4a4f (diff)
downloadlinux-b3b7c4795ccab5be71f080774c45bbbcc75c2aaf.tar.bz2
x86/MCE: Serialize sysfs changes
The check_interval file in /sys/devices/system/machinecheck/machinecheck<cpu number> directory is a global timer value for MCE polling. If it is changed by one CPU, mce_restart() broadcasts the event to other CPUs to delete and restart the MCE polling timer and __mcheck_cpu_init_timer() reinitializes the mce_timer variable. If more than one CPU writes a specific value to the check_interval file concurrently, mce_timer is not protected from such concurrent accesses and all kinds of explosions happen. Since only root can write to those sysfs variables, the issue is not a big deal security-wise. However, concurrent writes to these configuration variables is void of reason so the proper thing to do is to serialize the access with a mutex. Boris: - Make store_int_with_restart() use device_store_ulong() to filter out negative intervals - Limit min interval to 1 second - Correct locking - Massage commit message Signed-off-by: Seunghun Han <kkamagui@gmail.com> Signed-off-by: Borislav Petkov <bp@suse.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Tony Luck <tony.luck@intel.com> Cc: linux-edac <linux-edac@vger.kernel.org> Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/20180302202706.9434-1-kkamagui@gmail.com
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kernel/cpu/mcheck/mce.c22
1 files changed, 21 insertions, 1 deletions
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index b3323cab9139..466f47301334 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -56,6 +56,9 @@
static DEFINE_MUTEX(mce_log_mutex);
+/* sysfs synchronization */
+static DEFINE_MUTEX(mce_sysfs_mutex);
+
#define CREATE_TRACE_POINTS
#include <trace/events/mce.h>
@@ -2088,6 +2091,7 @@ static ssize_t set_ignore_ce(struct device *s,
if (kstrtou64(buf, 0, &new) < 0)
return -EINVAL;
+ mutex_lock(&mce_sysfs_mutex);
if (mca_cfg.ignore_ce ^ !!new) {
if (new) {
/* disable ce features */
@@ -2100,6 +2104,8 @@ static ssize_t set_ignore_ce(struct device *s,
on_each_cpu(mce_enable_ce, (void *)1, 1);
}
}
+ mutex_unlock(&mce_sysfs_mutex);
+
return size;
}
@@ -2112,6 +2118,7 @@ static ssize_t set_cmci_disabled(struct device *s,
if (kstrtou64(buf, 0, &new) < 0)
return -EINVAL;
+ mutex_lock(&mce_sysfs_mutex);
if (mca_cfg.cmci_disabled ^ !!new) {
if (new) {
/* disable cmci */
@@ -2123,6 +2130,8 @@ static ssize_t set_cmci_disabled(struct device *s,
on_each_cpu(mce_enable_ce, NULL, 1);
}
}
+ mutex_unlock(&mce_sysfs_mutex);
+
return size;
}
@@ -2130,8 +2139,19 @@ static ssize_t store_int_with_restart(struct device *s,
struct device_attribute *attr,
const char *buf, size_t size)
{
- ssize_t ret = device_store_int(s, attr, buf, size);
+ unsigned long old_check_interval = check_interval;
+ ssize_t ret = device_store_ulong(s, attr, buf, size);
+
+ if (check_interval == old_check_interval)
+ return ret;
+
+ if (check_interval < 1)
+ check_interval = 1;
+
+ mutex_lock(&mce_sysfs_mutex);
mce_restart();
+ mutex_unlock(&mce_sysfs_mutex);
+
return ret;
}