From 40adffec8c0090533dfaa863ced7901b60bbf1dc Mon Sep 17 00:00:00 2001 From: Johan Hovold Date: Thu, 10 Sep 2026 15:08:15 +0200 Subject: [PATCH] serial: fix TIOCMIWAIT race The task state must be updated before checking the wakeup condition to avoid missing a racing modem status update. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: sashiko-bot@kernel.org Link: https://lore.kernel.org/r/20260904115542.E20D11F00A3D@smtp.kernel.org Cc: stable@kernel.org Signed-off-by: Johan Hovold Link: https://patch.msgid.link/20260910130816.642699-4-johan@kernel.org Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/serial_core.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index 139b93876229..f7b30f77b231 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -1230,12 +1230,12 @@ static int uart_wait_modem_status(struct tty_struct *tty, struct uart_state *sta add_wait_queue(&port->delta_msr_wait, &wait); for (;;) { + set_current_state(TASK_INTERRUPTIBLE); + uart_port_lock_irq(uport); memcpy(&cnow, &uport->icount, sizeof(struct uart_icount)); uart_port_unlock_irq(uport); - set_current_state(TASK_INTERRUPTIBLE); - if (((arg & TIOCM_RNG) && (cnow.rng != cprev.rng)) || ((arg & TIOCM_DSR) && (cnow.dsr != cprev.dsr)) || ((arg & TIOCM_CD) && (cnow.dcd != cprev.dcd)) ||