6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Karl Mehltretter [ Upstream commit c3b5623fd97648f2747444aa8932ae604662df93 ] TTY device registration can fail before a cdev is allocated. Serial core keeps the port so setserial can still use it, and later removal passes the NULL cdev slot to cdev_del(), causing a NULL-pointer dereference. Only delete the cdev when the slot is not NULL. Fixes: a3a10ce3429e ("Avoid usb reset crashes by making tty_io cdevs truly dynamic") Fixes: da4c279942b0 ("serial: enable serdev support") Assisted-by: Claude:claude-fable-5 Signed-off-by: Karl Mehltretter Link: https://patch.msgid.link/20260731181844.11330-4-kmehltretter@gmail.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/tty/tty_io.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index dd7231d9cab96..07e6bf5f8c6ff 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -3327,7 +3327,7 @@ EXPORT_SYMBOL_GPL(tty_register_device_attr); void tty_unregister_device(struct tty_driver *driver, unsigned index) { device_destroy(&tty_class, MKDEV(driver->major, driver->minor_start) + index); - if (!(driver->flags & TTY_DRIVER_DYNAMIC_ALLOC)) { + if (!(driver->flags & TTY_DRIVER_DYNAMIC_ALLOC) && driver->cdevs[index]) { cdev_del(driver->cdevs[index]); driver->cdevs[index] = NULL; } -- 2.53.0