From 8df07fe93573e9e548d6645273e9bcb6eb74059e Mon Sep 17 00:00:00 2001 From: Johan Hovold Date: Wed, 30 Sep 2026 15:18:45 +0200 Subject: tty: fix saved termios reset race Resetting saved termios state on device registration is needed where a minor number can be reused for an entirely different device and where the old settings may prevent the port from even being opened (e.g. when CLOCAL is not set). Not all TTY drivers guarantee that the minor number is no longer in use when registering devices however, something which can lead to a use-after-free when closing a TTY (and saving its termios) races with re-registration. Add a new TTY_DRIVER_RESET_SAVED_TERMIOS flag to request that any saved termios state is reset on registration and only set it for drivers that make sure that the minor number is no longer in use. Fixes: 93857edd9829 ("tty: reset termios state on device registration") Reported-by: Chengfeng Ye Link: https://lore.kernel.org/20260926184154.3017929-1-nicoyip.dev@gmail.com Cc: stable@kernel.org # 4.12 Signed-off-by: Johan Hovold Link: https://patch.msgid.link/20260930131845.1809256-1-johan@kernel.org Signed-off-by: Greg Kroah-Hartman --- include/linux/tty_driver.h | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'include') diff --git a/include/linux/tty_driver.h b/include/linux/tty_driver.h index 1f2896e56..62e459c5d 100644 --- a/include/linux/tty_driver.h +++ b/include/linux/tty_driver.h @@ -73,6 +73,11 @@ struct serial_struct; * @TTY_DRIVER_NO_WORKQUEUE: * Do not create workqueue when tty_register_driver(). Whenever set, flip * buffer workqueue can be set by tty_port_link_wq() for every port. + * + * @TTY_DRIVER_RESET_SAVED_TERMIOS + * Reset any saved termios settings on device registration when reusing a + * minor number. Must only be set by drivers that guarantee that the minor + * number is no longer in use. */ enum tty_driver_flag { TTY_DRIVER_INSTALLED = BIT(0), @@ -84,6 +89,7 @@ enum tty_driver_flag { TTY_DRIVER_DYNAMIC_ALLOC = BIT(6), TTY_DRIVER_UNNUMBERED_NODE = BIT(7), TTY_DRIVER_NO_WORKQUEUE = BIT(8), + TTY_DRIVER_RESET_SAVED_TERMIOS = BIT(9), }; enum tty_driver_type { -- cgit v1.3.1