From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:54604 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751442AbeCLPiG (ORCPT ); Mon, 12 Mar 2018 11:38:06 -0400 Subject: Patch "x86/MCE: Serialize sysfs changes" has been added to the 3.18-stable tree To: kkamagui@gmail.com, bp@suse.de, gregkh@linuxfoundation.org, linux-edac@vger.kernel.org, tglx@linutronix.de, tony.luck@intel.com Cc: , From: Date: Mon, 12 Mar 2018 16:37:55 +0100 Message-ID: <1520869075110170@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled x86/MCE: Serialize sysfs changes to the 3.18-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: x86-mce-serialize-sysfs-changes.patch and it can be found in the queue-3.18 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From b3b7c4795ccab5be71f080774c45bbbcc75c2aaf Mon Sep 17 00:00:00 2001 From: Seunghun Han Date: Tue, 6 Mar 2018 15:21:43 +0100 Subject: x86/MCE: Serialize sysfs changes From: Seunghun Han commit b3b7c4795ccab5be71f080774c45bbbcc75c2aaf upstream. The check_interval file in /sys/devices/system/machinecheck/machinecheck 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 Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Cc: Greg Kroah-Hartman Cc: Tony Luck Cc: linux-edac Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/20180302202706.9434-1-kkamagui@gmail.com Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/cpu/mcheck/mce.c | 22 +++++++++++++++++++++- 1 file changed, 21 insertions(+), 1 deletion(-) --- a/arch/x86/kernel/cpu/mcheck/mce.c +++ b/arch/x86/kernel/cpu/mcheck/mce.c @@ -56,6 +56,9 @@ static DEFINE_MUTEX(mce_chrdev_read_mute rcu_read_lock_sched_held() || \ lockdep_is_held(&mce_chrdev_read_mutex)) +/* sysfs synchronization */ +static DEFINE_MUTEX(mce_sysfs_mutex); + #define CREATE_TRACE_POINTS #include @@ -2183,6 +2186,7 @@ static ssize_t set_ignore_ce(struct devi if (kstrtou64(buf, 0, &new) < 0) return -EINVAL; + mutex_lock(&mce_sysfs_mutex); if (mca_cfg.ignore_ce ^ !!new) { if (new) { /* disable ce features */ @@ -2195,6 +2199,8 @@ static ssize_t set_ignore_ce(struct devi on_each_cpu(mce_enable_ce, (void *)1, 1); } } + mutex_unlock(&mce_sysfs_mutex); + return size; } @@ -2207,6 +2213,7 @@ static ssize_t set_cmci_disabled(struct if (kstrtou64(buf, 0, &new) < 0) return -EINVAL; + mutex_lock(&mce_sysfs_mutex); if (mca_cfg.cmci_disabled ^ !!new) { if (new) { /* disable cmci */ @@ -2218,6 +2225,8 @@ static ssize_t set_cmci_disabled(struct on_each_cpu(mce_enable_ce, NULL, 1); } } + mutex_unlock(&mce_sysfs_mutex); + return size; } @@ -2225,8 +2234,19 @@ static ssize_t store_int_with_restart(st 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; } Patches currently in stable-queue which might be from kkamagui@gmail.com are queue-3.18/x86-mce-serialize-sysfs-changes.patch