From mboxrd@z Thu Jan 1 00:00:00 1970 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: base64 Subject: [3.18,04/25] x86/MCE: Serialize sysfs changes From: Greg Kroah-Hartman Message-Id: <20180316152232.936014427@linuxfoundation.org> Date: Fri, 16 Mar 2018 16:22:51 +0100 To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Seunghun Han , Borislav Petkov , Thomas Gleixner , Tony Luck , linux-edac List-ID: My4xOC1zdGFibGUgcmV2aWV3IHBhdGNoLiAgSWYgYW55b25lIGhhcyBhbnkgb2JqZWN0aW9ucywg cGxlYXNlIGxldCBtZSBrbm93LgoKLS0tLS0tLS0tLS0tLS0tLS0tCgpGcm9tOiBTZXVuZ2h1biBI YW4gPGtrYW1hZ3VpQGdtYWlsLmNvbT4KCmNvbW1pdCBiM2I3YzQ3OTVjY2FiNWJlNzFmMDgwNzc0 YzQ1YmJiY2M3NWMyYWFmIHVwc3RyZWFtLgoKVGhlIGNoZWNrX2ludGVydmFsIGZpbGUgaW4KCiAg L3N5cy9kZXZpY2VzL3N5c3RlbS9tYWNoaW5lY2hlY2svbWFjaGluZWNoZWNrPGNwdSBudW1iZXI+ CgpkaXJlY3RvcnkgaXMgYSBnbG9iYWwgdGltZXIgdmFsdWUgZm9yIE1DRSBwb2xsaW5nLiBJZiBp 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smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-category=clean score=-100 state=0; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=linuxfoundation.org header.result=pass header_is_org_domain=yes Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753125AbeCPRiQ (ORCPT ); Fri, 16 Mar 2018 13:38:16 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:33150 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753471AbeCPPXb (ORCPT ); Fri, 16 Mar 2018 11:23:31 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Seunghun Han , Borislav Petkov , Thomas Gleixner , Tony Luck , linux-edac Subject: [PATCH 3.18 04/25] x86/MCE: Serialize sysfs changes Date: Fri, 16 Mar 2018 16:22:51 +0100 Message-Id: <20180316152232.936014427@linuxfoundation.org> X-Mailer: git-send-email 2.16.2 In-Reply-To: <20180316152232.750180431@linuxfoundation.org> References: <20180316152232.750180431@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 3.18-stable review patch. If anyone has any objections, please let me know. ------------------ 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; }