From 757055ae8dedf5333af17b3b5b4b70ba9bc9da4e Mon Sep 17 00:00:00 2001 From: Petr Mladek Date: Wed, 11 Nov 2020 14:54:49 +0100 Subject: init/console: Use ttynull as a fallback when there is no console stdin, stdout, and stderr standard I/O stream are created for the init process. They are not available when there is no console registered for /dev/console. It might lead to a crash when the init process tries to use them, see the commit 48021f98130880dd742 ("printk: handle blank console arguments passed in."). Normally, ttySX and ttyX consoles are used as a fallback when no consoles are defined via the command line, device tree, or SPCR. But there will be no console registered when an invalid console name is configured or when the configured consoles do not exist on the system. Users even try to avoid the console intentionally, for example, by using console="" or console=null. It is used on production systems where the serial port or terminal are not visible to users. Pushing messages to these consoles would just unnecessary slowdown the system. Make sure that stdin, stdout, stderr, and /dev/console are always available by a fallback to the existing ttynull driver. It has been implemented for exactly this purpose but it was used only when explicitly configured. Reviewed-by: Greg Kroah-Hartman Reviewed-by: Guenter Roeck Tested-by: Guenter Roeck Acked-by: Sergey Senozhatsky Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20201111135450.11214-2-pmladek@suse.com --- include/linux/console.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'include/linux') diff --git a/include/linux/console.h b/include/linux/console.h index 4b1e26c4cb42..9c662e41cde5 100644 --- a/include/linux/console.h +++ b/include/linux/console.h @@ -187,9 +187,12 @@ extern int braille_register_console(struct console *, int index, extern int braille_unregister_console(struct console *); #ifdef CONFIG_TTY extern void console_sysfs_notify(void); +extern void register_ttynull_console(void); #else static inline void console_sysfs_notify(void) { } +static inline void register_ttynull_console(void) +{ } #endif extern bool console_suspend_enabled; -- cgit v1.2.3