diff options
Diffstat (limited to 'kernel/printk.c')
| -rw-r--r-- | kernel/printk.c | 175 |
1 files changed, 95 insertions, 80 deletions
diff --git a/kernel/printk.c b/kernel/printk.c index b2ebaee8c37..2ddbdc73aad 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -39,16 +39,11 @@ #include <linux/syslog.h> #include <linux/cpu.h> #include <linux/notifier.h> +#include <linux/rculist.h> #include <asm/uaccess.h> /* - * for_each_console() allows you to iterate on each console - */ -#define for_each_console(con) \ - for (con = console_drivers; con != NULL; con = con->next) - -/* * Architectures can override it: */ void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...) @@ -102,7 +97,7 @@ static int console_locked, console_suspended; /* * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars * It is also used in interesting ways to provide interlocking in - * release_console_sem(). + * console_unlock();. */ static DEFINE_SPINLOCK(logbuf_lock); @@ -261,6 +256,12 @@ static inline void boot_delay_msec(void) } #endif +#ifdef CONFIG_SECURITY_DMESG_RESTRICT +int dmesg_restrict = 1; +#else +int dmesg_restrict; +#endif + int do_syslog(int type, char __user *buf, int len, bool from_file) { unsigned i, j, limit, count; @@ -268,7 +269,20 @@ int do_syslog(int type, char __user *buf, int len, bool from_file) char c; int error = 0; - error = security_syslog(type, from_file); + /* + * If this is from /proc/kmsg we only do the capabilities checks + * at open time. + */ + if (type == SYSLOG_ACTION_OPEN || !from_file) { + if (dmesg_restrict && !capable(CAP_SYSLOG)) + goto warn; /* switch to return -EPERM after 2.6.39 */ + if ((type != SYSLOG_ACTION_READ_ALL && + type != SYSLOG_ACTION_SIZE_BUFFER) && + !capable(CAP_SYSLOG)) + goto warn; /* switch to return -EPERM after 2.6.39 */ + } + + error = security_syslog(type); if (error) return error; @@ -409,6 +423,12 @@ int do_syslog(int type, char __user *buf, int len, bool from_file) } out: return error; +warn: + /* remove after 2.6.39 */ + if (capable(CAP_SYS_ADMIN)) + WARN_ONCE(1, "Attempt to access syslog with CAP_SYS_ADMIN " + "but no CAP_SYSLOG (deprecated and denied).\n"); + return -EPERM; } SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len) @@ -481,7 +501,7 @@ static void _call_console_drivers(unsigned start, /* * Call the console drivers, asking them to write out * log_buf[start] to log_buf[end - 1]. - * The console_sem must be held. + * The console_lock must be held. */ static void call_console_drivers(unsigned start, unsigned end) { @@ -584,11 +604,11 @@ static int have_callable_console(void) * * This is printk(). It can be called from any context. We want it to work. * - * We try to grab the console_sem. If we succeed, it's easy - we log the output and + * We try to grab the console_lock. If we succeed, it's easy - we log the output and * call the console drivers. If we fail to get the semaphore we place the output * into the log buffer and return. The current holder of the console_sem will - * notice the new output in release_console_sem() and will send it to the - * consoles before releasing the semaphore. + * notice the new output in console_unlock(); and will send it to the + * consoles before releasing the lock. * * One effect of this deferred printing is that code which calls printk() and * then changes console_loglevel may break. This is because console_loglevel @@ -639,19 +659,19 @@ static inline int can_use_console(unsigned int cpu) /* * Try to get console ownership to actually show the kernel * messages from a 'printk'. Return true (and with the - * console_semaphore held, and 'console_locked' set) if it + * console_lock held, and 'console_locked' set) if it * is successful, false otherwise. * * This gets called with the 'logbuf_lock' spinlock held and * interrupts disabled. It should return with 'lockbuf_lock' * released but interrupts still disabled. */ -static int acquire_console_semaphore_for_printk(unsigned int cpu) +static int console_trylock_for_printk(unsigned int cpu) __releases(&logbuf_lock) { int retval = 0; - if (!try_acquire_console_sem()) { + if (console_trylock()) { retval = 1; /* @@ -807,12 +827,12 @@ asmlinkage int vprintk(const char *fmt, va_list args) * actual magic (print out buffers, wake up klogd, * etc). * - * The acquire_console_semaphore_for_printk() function + * The console_trylock_for_printk() function * will release 'logbuf_lock' regardless of whether it * actually gets the semaphore or not. */ - if (acquire_console_semaphore_for_printk(this_cpu)) - release_console_sem(); + if (console_trylock_for_printk(this_cpu)) + console_unlock(); lockdep_on(); out_restore_irqs: @@ -973,7 +993,7 @@ void suspend_console(void) if (!console_suspend_enabled) return; printk("Suspending console(s) (use no_console_suspend to debug)\n"); - acquire_console_sem(); + console_lock(); console_suspended = 1; up(&console_sem); } @@ -984,7 +1004,7 @@ void resume_console(void) return; down(&console_sem); console_suspended = 0; - release_console_sem(); + console_unlock(); } /** @@ -1007,21 +1027,21 @@ static int __cpuinit console_cpu_notify(struct notifier_block *self, case CPU_DYING: case CPU_DOWN_FAILED: case CPU_UP_CANCELED: - acquire_console_sem(); - release_console_sem(); + console_lock(); + console_unlock(); } return NOTIFY_OK; } /** - * acquire_console_sem - lock the console system for exclusive use. + * console_lock - lock the console system for exclusive use. * - * Acquires a semaphore which guarantees that the caller has + * Acquires a lock which guarantees that the caller has * exclusive access to the console system and the console_drivers list. * * Can sleep, returns nothing. */ -void acquire_console_sem(void) +void console_lock(void) { BUG_ON(in_interrupt()); down(&console_sem); @@ -1030,21 +1050,29 @@ void acquire_console_sem(void) console_locked = 1; console_may_schedule = 1; } -EXPORT_SYMBOL(acquire_console_sem); +EXPORT_SYMBOL(console_lock); -int try_acquire_console_sem(void) +/** + * console_trylock - try to lock the console system for exclusive use. + * + * Tried to acquire a lock which guarantees that the caller has + * exclusive access to the console system and the console_drivers list. + * + * returns 1 on success, and 0 on failure to acquire the lock. + */ +int console_trylock(void) { if (down_trylock(&console_sem)) - return -1; + return 0; if (console_suspended) { up(&console_sem); - return -1; + return 0; } console_locked = 1; console_may_schedule = 0; - return 0; + return 1; } -EXPORT_SYMBOL(try_acquire_console_sem); +EXPORT_SYMBOL(console_trylock); int is_console_locked(void) { @@ -1055,38 +1083,40 @@ static DEFINE_PER_CPU(int, printk_pending); void printk_tick(void) { - if (__get_cpu_var(printk_pending)) { - __get_cpu_var(printk_pending) = 0; + if (__this_cpu_read(printk_pending)) { + __this_cpu_write(printk_pending, 0); wake_up_interruptible(&log_wait); } } int printk_needs_cpu(int cpu) { - return per_cpu(printk_pending, cpu); + if (cpu_is_offline(cpu)) + printk_tick(); + return __this_cpu_read(printk_pending); } void wake_up_klogd(void) { if (waitqueue_active(&log_wait)) - __raw_get_cpu_var(printk_pending) = 1; + this_cpu_write(printk_pending, 1); } /** - * release_console_sem - unlock the console system + * console_unlock - unlock the console system * - * Releases the semaphore which the caller holds on the console system + * Releases the console_lock which the caller holds on the console system * and the console driver list. * - * While the semaphore was held, console output may have been buffered - * by printk(). If this is the case, release_console_sem() emits - * the output prior to releasing the semaphore. + * While the console_lock was held, console output may have been buffered + * by printk(). If this is the case, console_unlock(); emits + * the output prior to releasing the lock. * * If there is output waiting for klogd, we wake it up. * - * release_console_sem() may be called from any context. + * console_unlock(); may be called from any context. */ -void release_console_sem(void) +void console_unlock(void) { unsigned long flags; unsigned _con_start, _log_end; @@ -1119,7 +1149,7 @@ void release_console_sem(void) if (wake_klogd) wake_up_klogd(); } -EXPORT_SYMBOL(release_console_sem); +EXPORT_SYMBOL(console_unlock); /** * console_conditional_schedule - yield the CPU if required @@ -1128,7 +1158,7 @@ EXPORT_SYMBOL(release_console_sem); * if this CPU should yield the CPU to another task, do * so here. * - * Must be called within acquire_console_sem(). + * Must be called within console_lock();. */ void __sched console_conditional_schedule(void) { @@ -1149,14 +1179,14 @@ void console_unblank(void) if (down_trylock(&console_sem) != 0) return; } else - acquire_console_sem(); + console_lock(); console_locked = 1; console_may_schedule = 0; for_each_console(c) if ((c->flags & CON_ENABLED) && c->unblank) c->unblank(); - release_console_sem(); + console_unlock(); } /* @@ -1167,7 +1197,7 @@ struct tty_driver *console_device(int *index) struct console *c; struct tty_driver *driver = NULL; - acquire_console_sem(); + console_lock(); for_each_console(c) { if (!c->device) continue; @@ -1175,7 +1205,7 @@ struct tty_driver *console_device(int *index) if (driver) break; } - release_console_sem(); + console_unlock(); return driver; } @@ -1186,17 +1216,17 @@ struct tty_driver *console_device(int *index) */ void console_stop(struct console *console) { - acquire_console_sem(); + console_lock(); console->flags &= ~CON_ENABLED; - release_console_sem(); + console_unlock(); } EXPORT_SYMBOL(console_stop); void console_start(struct console *console) { - acquire_console_sem(); + console_lock(); console->flags |= CON_ENABLED; - release_console_sem(); + console_unlock(); } EXPORT_SYMBOL(console_start); @@ -1318,7 +1348,7 @@ void register_console(struct console *newcon) * Put this console in the list - keep the * preferred driver at the head of the list. */ - acquire_console_sem(); + console_lock(); if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) { newcon->next = console_drivers; console_drivers = newcon; @@ -1330,14 +1360,15 @@ void register_console(struct console *newcon) } if (newcon->flags & CON_PRINTBUFFER) { /* - * release_console_sem() will print out the buffered messages + * console_unlock(); will print out the buffered messages * for us. */ spin_lock_irqsave(&logbuf_lock, flags); con_start = log_start; spin_unlock_irqrestore(&logbuf_lock, flags); } - release_console_sem(); + console_unlock(); + console_sysfs_notify(); /* * By unregistering the bootconsoles after we enable the real console @@ -1373,7 +1404,7 @@ int unregister_console(struct console *console) return braille_unregister_console(console); #endif - acquire_console_sem(); + console_lock(); if (console_drivers == console) { console_drivers=console->next; res = 0; @@ -1395,7 +1426,8 @@ int unregister_console(struct console *console) if (console_drivers != NULL && console->flags & CON_CONSDEV) console_drivers->flags |= CON_CONSDEV; - release_console_sem(); + console_unlock(); + console_sysfs_notify(); return res; } EXPORT_SYMBOL(unregister_console); @@ -1479,7 +1511,7 @@ int kmsg_dump_register(struct kmsg_dumper *dumper) /* Don't allow registering multiple times */ if (!dumper->registered) { dumper->registered = 1; - list_add_tail(&dumper->list, &dump_list); + list_add_tail_rcu(&dumper->list, &dump_list); err = 0; } spin_unlock_irqrestore(&dump_list_lock, flags); @@ -1503,29 +1535,16 @@ int kmsg_dump_unregister(struct kmsg_dumper *dumper) spin_lock_irqsave(&dump_list_lock, flags); if (dumper->registered) { dumper->registered = 0; - list_del(&dumper->list); + list_del_rcu(&dumper->list); err = 0; } spin_unlock_irqrestore(&dump_list_lock, flags); + synchronize_rcu(); return err; } EXPORT_SYMBOL_GPL(kmsg_dump_unregister); -static const char * const kmsg_reasons[] = { - [KMSG_DUMP_OOPS] = "oops", - [KMSG_DUMP_PANIC] = "panic", - [KMSG_DUMP_KEXEC] = "kexec", -}; - -static const char *kmsg_to_str(enum kmsg_dump_reason reason) -{ - if (reason >= ARRAY_SIZE(kmsg_reasons) || reason < 0) - return "unknown"; - - return kmsg_reasons[reason]; -} - /** * kmsg_dump - dump kernel log to kernel message dumpers. * @reason: the reason (oops, panic etc) for dumping @@ -1564,13 +1583,9 @@ void kmsg_dump(enum kmsg_dump_reason reason) l2 = chars; } - if (!spin_trylock_irqsave(&dump_list_lock, flags)) { - printk(KERN_ERR "dump_kmsg: dump list lock is held during %s, skipping dump\n", - kmsg_to_str(reason)); - return; - } - list_for_each_entry(dumper, &dump_list, list) + rcu_read_lock(); + list_for_each_entry_rcu(dumper, &dump_list, list) dumper->dump(dumper, reason, s1, l1, s2, l2); - spin_unlock_irqrestore(&dump_list_lock, flags); + rcu_read_unlock(); } #endif |