diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index e24aa11e8f8a..b240540e49f2 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3173,6 +3173,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
 			default: disabled
 
+	printk.devkmsg={on,off,ratelimit}
+			Control writing to /dev/kmsg.
+			on - unlimited logging to /dev/kmsg from userspace
+			off - logging to /dev/kmsg disabled
+			ratelimit - ratelimit the logging
+			Default: ratelimit
+
 	printk.time=	Show timing data prefixed to each printk message line
 			Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
 
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index 33204604de6c..ffab8b5caa60 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -764,6 +764,20 @@ send before ratelimiting kicks in.
 
 ==============================================================
 
+printk_devkmsg:
+
+Control the logging to /dev/kmsg from userspace:
+
+ratelimit: default, ratelimited
+on: unlimited logging to /dev/kmsg from userspace
+off: logging to /dev/kmsg disabled
+
+The kernel command line parameter printk.devkmsg= overrides this and is
+a one-time setting until next reboot: once set, it cannot be changed by
+this sysctl interface anymore.
+
+==============================================================
+
 randomize_va_space:
 
 This option can be used to select the type of process address
diff --git a/include/linux/printk.h b/include/linux/printk.h
index c2158f0f1499..8dc155dab3ed 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -61,6 +61,11 @@ static inline void console_verbose(void)
 		console_loglevel = CONSOLE_LOGLEVEL_MOTORMOUTH;
 }
 
+/* strlen("ratelimit") + 1 */
+#define DEVKMSG_STR_MAX_SIZE 10
+extern char devkmsg_log_str[];
+struct ctl_table;
+
 struct va_format {
 	const char *fmt;
 	va_list *va;
@@ -175,6 +180,10 @@ extern int printk_delay_msec;
 extern int dmesg_restrict;
 extern int kptr_restrict;
 
+extern int
+devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write, void __user *buf,
+			  size_t *lenp, loff_t *ppos);
+
 extern void wake_up_klogd(void);
 
 char *log_buf_addr_get(void);
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 70c66c5ba212..a5ef95ca18c9 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -85,6 +85,111 @@ static struct lockdep_map console_lock_dep_map = {
 };
 #endif
 
+enum devkmsg_log_bits {
+	__DEVKMSG_LOG_BIT_ON = 0,
+	__DEVKMSG_LOG_BIT_OFF,
+	__DEVKMSG_LOG_BIT_LOCK,
+};
+
+enum devkmsg_log_masks {
+	DEVKMSG_LOG_MASK_ON             = BIT(__DEVKMSG_LOG_BIT_ON),
+	DEVKMSG_LOG_MASK_OFF            = BIT(__DEVKMSG_LOG_BIT_OFF),
+	DEVKMSG_LOG_MASK_LOCK           = BIT(__DEVKMSG_LOG_BIT_LOCK),
+};
+
+/* Keep both the 'on' and 'off' bits clear, i.e. ratelimit by default: */
+#define DEVKMSG_LOG_MASK_DEFAULT	0
+
+static unsigned int __read_mostly devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT;
+
+static int __control_devkmsg(char *str)
+{
+	if (!str)
+		return -EINVAL;
+
+	if (!strncmp(str, "on", 2)) {
+		devkmsg_log = DEVKMSG_LOG_MASK_ON;
+		return 2;
+	} else if (!strncmp(str, "off", 3)) {
+		devkmsg_log = DEVKMSG_LOG_MASK_OFF;
+		return 3;
+	} else if (!strncmp(str, "ratelimit", 9)) {
+		devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT;
+		return 9;
+	}
+	return -EINVAL;
+}
+
+static int __init control_devkmsg(char *str)
+{
+	if (__control_devkmsg(str) < 0)
+		return 1;
+
+	/*
+	 * Set sysctl string accordingly:
+	 */
+	if (devkmsg_log == DEVKMSG_LOG_MASK_ON) {
+		memset(devkmsg_log_str, 0, DEVKMSG_STR_MAX_SIZE);
+		strncpy(devkmsg_log_str, "on", 2);
+	} else if (devkmsg_log == DEVKMSG_LOG_MASK_OFF) {
+		memset(devkmsg_log_str, 0, DEVKMSG_STR_MAX_SIZE);
+		strncpy(devkmsg_log_str, "off", 3);
+	}
+	/* else "ratelimit" which is set by default. */
+
+	/*
+	 * Sysctl cannot change it anymore. The kernel command line setting of
+	 * this parameter is to force the setting to be permanent throughout the
+	 * runtime of the system. This is a precation measure against userspace
+	 * trying to be a smarta** and attempting to change it up on us.
+	 */
+	devkmsg_log |= DEVKMSG_LOG_MASK_LOCK;
+
+	return 0;
+}
+__setup("printk.devkmsg=", control_devkmsg);
+
+char devkmsg_log_str[DEVKMSG_STR_MAX_SIZE] = "ratelimit";
+
+int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write,
+			      void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+	char old_str[DEVKMSG_STR_MAX_SIZE];
+	unsigned int old;
+	int err;
+
+	if (write) {
+		if (devkmsg_log & DEVKMSG_LOG_MASK_LOCK)
+			return -EINVAL;
+
+		old = devkmsg_log;
+		strncpy(old_str, devkmsg_log_str, DEVKMSG_STR_MAX_SIZE);
+	}
+
+	err = proc_dostring(table, write, buffer, lenp, ppos);
+	if (err)
+		return err;
+
+	if (write) {
+		err = __control_devkmsg(devkmsg_log_str);
+
+		/*
+		 * Do not accept an unknown string OR a known string with
+		 * trailing crap...
+		 */
+		if (err < 0 || (err + 1 != *lenp)) {
+
+			/* ... and restore old setting. */
+			devkmsg_log = old;
+			strncpy(devkmsg_log_str, old_str, DEVKMSG_STR_MAX_SIZE);
+
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
 /*
  * Number of registered extended console drivers.
  *
@@ -613,6 +718,7 @@ struct devkmsg_user {
 	u64 seq;
 	u32 idx;
 	enum log_flags prev;
+	struct ratelimit_state rs;
 	struct mutex lock;
 	char buf[CONSOLE_EXT_LOG_MAX];
 };
@@ -622,11 +728,24 @@ static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from)
 	char *buf, *line;
 	int level = default_message_loglevel;
 	int facility = 1;	/* LOG_USER */
+	struct file *file = iocb->ki_filp;
+	struct devkmsg_user *user = file->private_data;
 	size_t len = iov_iter_count(from);
 	ssize_t ret = len;
 
-	if (len > LOG_LINE_MAX)
+	if (!user || len > LOG_LINE_MAX)
 		return -EINVAL;
+
+	/* Ignore when user logging is disabled. */
+	if (devkmsg_log & DEVKMSG_LOG_MASK_OFF)
+		return len;
+
+	/* Ratelimit when not explicitly enabled. */
+	if (!(devkmsg_log & DEVKMSG_LOG_MASK_ON)) {
+		if (!___ratelimit(&user->rs, current->comm))
+			return ret;
+	}
+
 	buf = kmalloc(len+1, GFP_KERNEL);
 	if (buf == NULL)
 		return -ENOMEM;
@@ -799,19 +918,24 @@ static int devkmsg_open(struct inode *inode, struct file *file)
 	struct devkmsg_user *user;
 	int err;
 
-	/* write-only does not need any file context */
-	if ((file->f_flags & O_ACCMODE) == O_WRONLY)
-		return 0;
+	if (devkmsg_log & DEVKMSG_LOG_MASK_OFF)
+		return -EPERM;
 
-	err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
-				       SYSLOG_FROM_READER);
-	if (err)
-		return err;
+	/* write-only does not need any file context */
+	if ((file->f_flags & O_ACCMODE) != O_WRONLY) {
+		err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
+					       SYSLOG_FROM_READER);
+		if (err)
+			return err;
+	}
 
 	user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
 	if (!user)
 		return -ENOMEM;
 
+	ratelimit_default_init(&user->rs);
+	ratelimit_set_flags(&user->rs, RATELIMIT_MSG_ON_RELEASE);
+
 	mutex_init(&user->lock);
 
 	raw_spin_lock_irq(&logbuf_lock);
@@ -830,6 +954,8 @@ static int devkmsg_release(struct inode *inode, struct file *file)
 	if (!user)
 		return 0;
 
+	ratelimit_state_exit(&user->rs);
+
 	mutex_destroy(&user->lock);
 	kfree(user);
 	return 0;
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 53954631a4e1..b43d0b27c1fe 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -813,6 +813,13 @@ static struct ctl_table kern_table[] = {
 		.extra1		= &zero,
 		.extra2		= &ten_thousand,
 	},
+	{
+		.procname	= "printk_devkmsg",
+		.data		= devkmsg_log_str,
+		.maxlen		= DEVKMSG_STR_MAX_SIZE,
+		.mode		= 0644,
+		.proc_handler	= devkmsg_sysctl_set_loglvl,
+	},
 	{
 		.procname	= "dmesg_restrict",
 		.data		= &dmesg_restrict,