printk: check CON_ENABLED in have_callable_console()

have_callable_console() must also test CON_ENABLED bit, not just
CON_ANYTIME.  We may have disabled CON_ANYTIME console so printk can
wrongly assume that it's safe to call_console_drivers().

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Jan Kara <jack@suse.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Kyle McMartin <kyle@kernel.org>
Cc: Dave Jones <davej@codemonkey.org.uk>
Cc: Calvin Owens <calvinowens@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index a6d023c..d5fd844 100644 (file)
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2146,7 +2146,8 @@ static int have_callable_console(void)
        struct console *con;
 
        for_each_console(con)
-               if (con->flags & CON_ANYTIME)
+               if ((con->flags & CON_ENABLED) &&
+                               (con->flags & CON_ANYTIME))
                        return 1;
 
        return 0;