From: John Ogness Date: Wed, 16 Nov 2022 16:21:49 +0000 (+0106) Subject: tty: serial: kgdboc: synchronize tty_find_polling_driver() and register_console() X-Git-Tag: v6.2-rc1~213^2^2~4 X-Git-Url: https://repo.jachan.dev/linux.git/commitdiff_plain/6193bc90849a tty: serial: kgdboc: synchronize tty_find_polling_driver() and register_console() Calling tty_find_polling_driver() can lead to uart_set_options() being called (via the poll_init() callback of tty_operations) to configure the uart. But uart_set_options() can also be called by register_console() (via the setup() callback of console). Take the console_list_lock to synchronize against register_console() and also use it for console list traversal. This also ensures the console list cannot change until the polling console has been chosen. Signed-off-by: John Ogness Reviewed-by: Daniel Thompson Reviewed-by: Petr Mladek Reviewed-by: Douglas Anderson Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20221116162152.193147-38-john.ogness@linutronix.de --- diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c index 82b4b4d67823..8c2b7ccdfebf 100644 --- a/drivers/tty/serial/kgdboc.c +++ b/drivers/tty/serial/kgdboc.c @@ -189,12 +189,20 @@ static int configure_kgdboc(void) if (kgdboc_register_kbd(&cptr)) goto do_register; + /* + * tty_find_polling_driver() can call uart_set_options() + * (via poll_init) to configure the uart. Take the console_list_lock + * in order to synchronize against register_console(), which can also + * configure the uart via uart_set_options(). This also allows safe + * traversal of the console list. + */ + console_list_lock(); + p = tty_find_polling_driver(cptr, &tty_line); - if (!p) + if (!p) { + console_list_unlock(); goto noconfig; - - /* For safe traversal of the console list. */ - console_list_lock(); + } /* * Take console_lock to serialize device() callback with