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-rw-r--r--Documentation/kernel-parameters.txt7
-rw-r--r--Documentation/sysctl/kernel.txt14
-rw-r--r--include/linux/printk.h9
-rw-r--r--kernel/printk/printk.c142
-rw-r--r--kernel/sysctl.c7
5 files changed, 171 insertions, 8 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index e24aa11..b240540 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 3320460..ffab8b5 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 c2158f0..8dc155d 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 70c66c5..a5ef95c 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 5395463..b43d0b2 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -814,6 +814,13 @@ static struct ctl_table kern_table[] = {
.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,
.maxlen = sizeof(int),