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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
This commit is contained in:
Seunghun Han 2018-03-06 15:21:43 +01:00 committed by Thomas Gleixner
parent fa94d0c6e0
commit b3b7c4795c
1 changed files with 21 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
arch/x86/kernel/cpu/mcheck/mce.c
View File

@ -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;
}