diff options
| -rw-r--r-- | Documentation/kernel-parameters.txt | 7 | ||||
| -rw-r--r-- | Documentation/sysctl/kernel.txt | 14 | ||||
| -rw-r--r-- | include/linux/printk.h | 9 | ||||
| -rw-r--r-- | kernel/printk/printk.c | 142 | ||||
| -rw-r--r-- | kernel/sysctl.c | 7 |
5 files changed, 171 insertions, 8 deletions
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 @@ -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), |