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: [4.9,28/86] x86/MCE: Serialize sysfs changes From: Greg Kroah-Hartman Message-Id: <20180316152319.335748145@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: NC45LXN0YWJsZSByZXZpZXcgcGF0Y2guICBJZiBhbnlvbmUgaGFzIGFueSBvYmplY3Rpb25zLCBw bGVhc2UgbGV0IG1lIGtub3cuCgotLS0tLS0tLS0tLS0tLS0tLS0KCkZyb206IFNldW5naHVuIEhh biA8a2thbWFndWlAZ21haWwuY29tPgoKY29tbWl0IGIzYjdjNDc5NWNjYWI1YmU3MWYwODA3NzRj NDViYmJjYzc1YzJhYWYgdXBzdHJlYW0uCgpUaGUgY2hlY2tfaW50ZXJ2YWwgZmlsZSBpbgoKICAv c3lzL2RldmljZXMvc3lzdGVtL21hY2hpbmVjaGVjay9tYWNoaW5lY2hlY2s8Y3B1IG51bWJlcj4K CmRpcmVjdG9yeSBpcyBhIGdsb2JhbCB0aW1lciB2YWx1ZSBmb3IgTUNFIHBvbGxpbmcuIElmIGl0 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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; }