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 --- init/main.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) (limited to 'init/main.c') diff --git a/init/main.c b/init/main.c index 1af84337cb18..b3fcf446f99e 100644 --- a/init/main.c +++ b/init/main.c @@ -1468,8 +1468,14 @@ void __init console_on_rootfs(void) struct file *file = filp_open("/dev/console", O_RDWR, 0); if (IS_ERR(file)) { - pr_err("Warning: unable to open an initial console.\n"); - return; + pr_err("Warning: unable to open an initial console. Fallback to ttynull.\n"); + register_ttynull_console(); + + file = filp_open("/dev/console", O_RDWR, 0); + if (IS_ERR(file)) { + pr_err("Warning: Failed to add ttynull console. No stdin, stdout, and stderr for the init process!\n"); + return; + } } init_dup(file); init_dup(file); -- cgit v1.2.3-58-ga151