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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 <john.ogness@linutronix.de>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20221116162152.193147-38-john.ogness@linutronix.de
This commit is contained in:
John Ogness 2022-11-16 17:27:49 +01:06 committed by Petr Mladek
parent 6685744369
commit 6193bc9084
1 changed files with 13 additions and 5 deletions
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18
drivers/tty/serial/kgdboc.c
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@ -189,13 +189,21 @@ static int configure_kgdboc(void)
if (kgdboc_register_kbd(&cptr))
goto do_register;
p = tty_find_polling_driver(cptr, &tty_line);
if (!p)
goto noconfig;
/* For safe traversal of the console list. */
/*
* 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) {
console_list_unlock();
goto noconfig;
}
/*
* Take console_lock to serialize device() callback with
* other console operations. For example, fg_console is