patch "USB: serial: keyspan_pda: fix write deadlock" added to usb-next

patch "USB: serial: keyspan_pda: fix write deadlock" added to usb-next

[gregkh]

This is a note to let you know that I've just added the patch titled

    USB: serial: keyspan_pda: fix write deadlock

to my usb git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-next branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will also be merged in the next major kernel release
during the merge window.

If you have any questions about this process, please let me know.


From 7353cad7ee4deaefc16e94727e69285563e219f6 Mon Sep 17 00:00:00 2001
From: Johan Hovold <johan@kernel.org>
Date: Sun, 25 Oct 2020 18:45:48 +0100
Subject: USB: serial: keyspan_pda: fix write deadlock

The write() callback can be called in interrupt context (e.g. when used
as a console) so interrupts must be disabled while holding the port lock
to prevent a possible deadlock.

Fixes: e81ee637e4ae ("usb-serial: possible irq lock inversion (PPP vs. usb/serial)")
Fixes: 507ca9bc0476 ("[PATCH] USB: add ability for usb-serial drivers to determine if their write urb is currently being used.")
Cc: stable <stable@vger.kernel.org>     # 2.6.19
Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/usb/serial/keyspan_pda.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/serial/keyspan_pda.c b/drivers/usb/serial/keyspan_pda.c
index 2d5ad579475a..17b60e5a9f1f 100644
--- a/drivers/usb/serial/keyspan_pda.c
+++ b/drivers/usb/serial/keyspan_pda.c
@@ -443,6 +443,7 @@ static int keyspan_pda_write(struct tty_struct *tty,
 	int request_unthrottle = 0;
 	int rc = 0;
 	struct keyspan_pda_private *priv;
+	unsigned long flags;
 
 	priv = usb_get_serial_port_data(port);
 	/* guess how much room is left in the device's ring buffer, and if we
@@ -462,13 +463,13 @@ static int keyspan_pda_write(struct tty_struct *tty,
 	   the TX urb is in-flight (wait until it completes)
 	   the device is full (wait until it says there is room)
 	*/
-	spin_lock_bh(&port->lock);
+	spin_lock_irqsave(&port->lock, flags);
 	if (!test_bit(0, &port->write_urbs_free) || priv->tx_throttled) {
-		spin_unlock_bh(&port->lock);
+		spin_unlock_irqrestore(&port->lock, flags);
 		return 0;
 	}
 	clear_bit(0, &port->write_urbs_free);
-	spin_unlock_bh(&port->lock);
+	spin_unlock_irqrestore(&port->lock, flags);
 
 	/* At this point the URB is in our control, nobody else can submit it
 	   again (the only sudden transition was the one from EINPROGRESS to
-- 
2.29.2