From: Borislav Petkov <bp@alien8.de>
To: X86 ML <x86@kernel.org>
Cc: Tony Luck <tony.luck@intel.com>, LKML <linux-kernel@vger.kernel.org>
Subject: [PATCH 3/3] x86/MCE: Synchronize sysfs changes
Date: Tue, 6 Mar 2018 15:21:43 +0100 [thread overview]
Message-ID: <20180306142143.19990-4-bp@alien8.de> (raw)
In-Reply-To: <20180306142143.19990-1-bp@alien8.de>
From: Seunghun Han <kkamagui@gmail.com>
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 "slow" accesses
down by synchronizing them with a mutex and thus take care of the
synchronization issue too.
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>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
Cc: x86-ml <x86@kernel.org>
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/20180302202706.9434-1-kkamagui@gmail.com
Signed-off-by: Borislav Petkov <bp@suse.de>
---
arch/x86/kernel/cpu/mcheck/mce.c | 22 +++++++++++++++++++++-
1 file changed, 21 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 181f6cf25895..21962c48dad7 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>
@@ -2104,6 +2107,7 @@ 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 */
@@ -2116,6 +2120,8 @@ 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;
}
@@ -2128,6 +2134,7 @@ 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 */
@@ -2139,6 +2146,8 @@ static ssize_t set_cmci_disabled(struct device *s,
on_each_cpu(mce_enable_ce, NULL, 1);
}
}
+ mutex_unlock(&mce_sysfs_mutex);
+
return size;
}
@@ -2146,8 +2155,19 @@ 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;
}
--
2.13.0
prev parent reply other threads:[~2018-03-06 14:22 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-06 14:21 [PATCH 0/3] x86/RAS: Some more fixes Borislav Petkov
2018-03-06 14:21 ` [PATCH 1/3] x86/MCE: Save microcode revision in machine check records Borislav Petkov
2018-03-06 14:21 ` [PATCH 2/3] x86/MCE: Cleanup and complete struct mce fields definitions Borislav Petkov
2018-03-08 15:00 ` [tip:ras/core] " tip-bot for Borislav Petkov
2018-03-06 14:21 ` Borislav Petkov [this message]
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