From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AG47ELu8DhWHe+UpMfgCykc/ZtA6k/Ny2L0nkztiEKAVi0kj2jdTJhxOIeRTigpOQdMktMINvwQP ARC-Seal: i=1; a=rsa-sha256; t=1521214258; cv=none; d=google.com; s=arc-20160816; b=QMsJFfocxkNt3j9zS6/8QmxnuwQK1kZrc/VIkvFHUycCXcjHHeEd/L5qTBiPISv+iW 3qMLeKjpiHkoR2AKu+QqIWen1xmgyCyrAvKnmT7wke8FJSLt2KDqnzoHZSJI4tM1ylnG IW9OkybohPz1X/CSSQukjo1qmS6xcTZtXr6ws3v35HfCiuCqUvv0le6J1Or6HBXU2LnC 0o8ghOH2Yq1O4NCtSuq39+XxMpWwTi06A+gABUulD/T4DYgeNsUI9ScC2+Z3wu1rhXy8 gxlK4outSLK4niRbWqJ1BPuLy2bsKt2V/O5Vv0ct3PwzBQGRV803ov0XFHre9JPDgY8i aHag== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:user-agent:references:in-reply-to:message-id:date :subject:cc:to:from:arc-authentication-results; bh=5u3vjJ3Jm3jUU5CM536draNIQsLpICMwElIfVmkGdQc=; b=apeQn/YHfHjdCXY+F9CC9Y+pzvAC9Trfg+gdb2PlXHIVDn4qxpX3h5YLwQukDxVODx lQDW9rEQwQH2qkhpQ7G9Nd23MeuXfDUUdJRwLmw64XtIGupZSLuh1biKZrWFz9+14Fje 7IPIdWHYVodYibSaiBwX/zEnk36/vFVhktQPwO0cvySHrb7clUTC/2ySbTk0vP0+GYFj UrRiNm/c5rNsp/VflNmWyePqi37Y+orIBJy3JRzbT1tZdx0ap8p5laQehgMrHgZ9tNzn C4M/iEsLviBpCHYmNYQh2SOPR1xvYBJBD3j4L/PHgPmZLQR3QBCqMTb8jxWTJnennl2y vBPA== ARC-Authentication-Results: i=1; mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.61.202 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.61.202 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org 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 4.9 28/86] x86/MCE: Serialize sysfs changes Date: Fri, 16 Mar 2018 16:22:51 +0100 Message-Id: <20180316152319.335748145@linuxfoundation.org> X-Mailer: git-send-email 2.16.2 In-Reply-To: <20180316152317.167709497@linuxfoundation.org> References: <20180316152317.167709497@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcU2VudCI=?= X-GMAIL-THRID: =?utf-8?q?1595108292811892931?= X-GMAIL-MSGID: =?utf-8?q?1595108762294509343?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.9-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 @@ -61,6 +61,9 @@ static DEFINE_MUTEX(mce_chrdev_read_mute smp_load_acquire(&(p)); \ }) +/* sysfs synchronization */ +static DEFINE_MUTEX(mce_sysfs_mutex); + #define CREATE_TRACE_POINTS #include @@ -2308,6 +2311,7 @@ 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 */ @@ -2320,6 +2324,8 @@ static ssize_t set_ignore_ce(struct devi on_each_cpu(mce_enable_ce, (void *)1, 1); } } + mutex_unlock(&mce_sysfs_mutex); + return size; } @@ -2332,6 +2338,7 @@ 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 */ @@ -2343,6 +2350,8 @@ static ssize_t set_cmci_disabled(struct on_each_cpu(mce_enable_ce, NULL, 1); } } + mutex_unlock(&mce_sysfs_mutex); + return size; } @@ -2350,8 +2359,19 @@ 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; }