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: [tip:ras/urgent] x86/MCE: Serialize sysfs changes From: tip-bot for Borislav Petkov Message-Id: Date: Thu, 8 Mar 2018 06:40:20 -0800 To: linux-tip-commits@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kkamagui@gmail.com, tony.luck@intel.com, tglx@linutronix.de, bp@suse.de, hpa@zytor.com, linux-edac@vger.kernel.org, mingo@kernel.org, gregkh@linuxfoundation.org List-ID: Q29tbWl0LUlEOiAgYjNiN2M0Nzk1Y2NhYjViZTcxZjA4MDc3NGM0NWJiYmNjNzVjMmFhZgpHaXR3 ZWI6ICAgICBodHRwczovL2dpdC5rZXJuZWwub3JnL3RpcC9iM2I3YzQ3OTVjY2FiNWJlNzFmMDgw Nzc0YzQ1YmJiY2M3NWMyYWFmCkF1dGhvcjogICAgIFNldW5naHVuIEhhbiA8a2thbWFndWlAZ21h aWwuY29tPgpBdXRob3JEYXRlOiBUdWUsIDYgTWFyIDIwMTggMTU6MjE6NDMgKzAxMDAKQ29tbWl0 dGVyOiAgVGhvbWFzIEdsZWl4bmVyIDx0Z2x4QGxpbnV0cm9uaXguZGU+CkNvbW1pdERhdGU6IFRo dSwgOCBNYXIgMjAxOCAxNTozNjoyNyArMDEwMAoKeDg2L01DRTogU2VyaWFsaXplIHN5c2ZzIGNo 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of tipbot@zytor.com designates 198.137.202.136 as permitted sender) smtp.mailfrom=tipbot@zytor.com Authentication-Results: mx.google.com; spf=pass (google.com: domain of tipbot@zytor.com designates 198.137.202.136 as permitted sender) smtp.mailfrom=tipbot@zytor.com Date: Thu, 8 Mar 2018 06:40:20 -0800 Sender: tip tree robot From: tip-bot for Seunghun Han Message-ID: Cc: linux-kernel@vger.kernel.org, kkamagui@gmail.com, tony.luck@intel.com, tglx@linutronix.de, bp@suse.de, hpa@zytor.com, linux-edac@vger.kernel.org, mingo@kernel.org, gregkh@linuxfoundation.org Reply-To: hpa@zytor.com, gregkh@linuxfoundation.org, mingo@kernel.org, linux-edac@vger.kernel.org, tony.luck@intel.com, kkamagui@gmail.com, linux-kernel@vger.kernel.org, bp@suse.de, tglx@linutronix.de In-Reply-To: <20180302202706.9434-1-kkamagui@gmail.com> References: <20180302202706.9434-1-kkamagui@gmail.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:ras/urgent] x86/MCE: Serialize sysfs changes Git-Commit-ID: b3b7c4795ccab5be71f080774c45bbbcc75c2aaf X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1594380809723141993?= X-GMAIL-MSGID: =?utf-8?q?1594380809723141993?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: Commit-ID: b3b7c4795ccab5be71f080774c45bbbcc75c2aaf Gitweb: https://git.kernel.org/tip/b3b7c4795ccab5be71f080774c45bbbcc75c2aaf Author: Seunghun Han AuthorDate: Tue, 6 Mar 2018 15:21:43 +0100 Committer: Thomas Gleixner CommitDate: Thu, 8 Mar 2018 15:36:27 +0100 x86/MCE: Serialize sysfs changes 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 --- 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 b3323cab9139..466f47301334 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 @@ -2088,6 +2091,7 @@ 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 */ @@ -2100,6 +2104,8 @@ 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; } @@ -2112,6 +2118,7 @@ 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 */ @@ -2123,6 +2130,8 @@ static ssize_t set_cmci_disabled(struct device *s, on_each_cpu(mce_enable_ce, NULL, 1); } } + mutex_unlock(&mce_sysfs_mutex); + return size; } @@ -2130,8 +2139,19 @@ 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; }