1 files changed, 28 insertions, 6 deletions

diff --git a/kernel/printk.c b/kernel/printk.c
index 8fe465ac008a..a23315dc4498 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -85,7 +85,7 @@ EXPORT_SYMBOL(oops_in_progress);
  * provides serialisation for access to the entire console
  * driver system.
  */
-static DECLARE_MUTEX(console_sem);
+static DEFINE_SEMAPHORE(console_sem);
 struct console *console_drivers;
 EXPORT_SYMBOL_GPL(console_drivers);
 
@@ -210,7 +210,7 @@ __setup("log_buf_len=", log_buf_len_setup);
 
 #ifdef CONFIG_BOOT_PRINTK_DELAY
 
-static unsigned int boot_delay; /* msecs delay after each printk during bootup */
+static int boot_delay; /* msecs delay after each printk during bootup */
 static unsigned long long loops_per_msec;       /* based on boot_delay */
 
 static int __init boot_delay_setup(char *str)
@@ -261,6 +261,12 @@ 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 +274,20 @@ 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_SYS_ADMIN))
+                        return -EPERM;
+                if ((type != SYSLOG_ACTION_READ_ALL &&
+                     type != SYSLOG_ACTION_SIZE_BUFFER) &&
+                    !capable(CAP_SYS_ADMIN))
+                        return -EPERM;
+        }
+
+        error = security_syslog(type);
         if (error)
                 return error;
 
@@ -556,7 +575,7 @@ static void zap_locks(void)
         /* If a crash is occurring, make sure we can't deadlock */
         spin_lock_init(&logbuf_lock);
         /* And make sure that we print immediately */
-        init_MUTEX(&console_sem);
+        sema_init(&console_sem, 1);
 }
 
 #if defined(CONFIG_PRINTK_TIME)
@@ -647,6 +666,7 @@ static inline int can_use_console(unsigned int cpu)
  * released but interrupts still disabled.
  */
 static int acquire_console_semaphore_for_printk(unsigned int cpu)
+        __releases(&logbuf_lock)
 {
         int retval = 0;
 
@@ -1062,13 +1082,15 @@ void printk_tick(void)
 
 int printk_needs_cpu(int cpu)
 {
+        if (unlikely(cpu_is_offline(cpu)))
+                printk_tick();
         return per_cpu(printk_pending, cpu);
 }
 
 void wake_up_klogd(void)
 {
         if (waitqueue_active(&log_wait))
-                __raw_get_cpu_var(printk_pending) = 1;
+                this_cpu_write(printk_pending, 1);
 }
 
 /**
@@ -1511,7 +1533,7 @@ int kmsg_dump_unregister(struct kmsg_dumper *dumper)
 }
 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
 
-static const char const *kmsg_reasons[] = {
+static const char * const kmsg_reasons[] = {
         [KMSG_DUMP_OOPS]        = "oops",
         [KMSG_DUMP_PANIC]       = "panic",
         [KMSG_DUMP_KEXEC]       = "kexec",