Patch "serial: 8250_pci: fix divide error bug if baud rate is 0" has been added to the 4.4-stable tree

Patch "serial: 8250_pci: fix divide error bug if baud rate is 0" has been added to the 4.4-stable tree

[gregkh]

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

    serial: 8250_pci: fix divide error bug if baud rate is 0

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     serial-8250_pci-fix-divide-error-bug-if-baud-rate-is-0.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 6f210c18c1c0f016772c8cd51ae12a02bfb9e7ef Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?David=20M=C3=BCller?= <d.mueller@elsoft.ch>
Date: Wed, 27 Apr 2016 11:58:32 +0200
Subject: serial: 8250_pci: fix divide error bug if baud rate is 0
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

From: David Müller <d.mueller@elsoft.ch>

commit 6f210c18c1c0f016772c8cd51ae12a02bfb9e7ef upstream.

Since commit 21947ba654a6 ("serial: 8250_pci: replace switch-case by
formula"), the 8250 driver crashes in the byt_set_termios() function
with a divide error. This is caused by the fact that a baud rate of 0 (B0)
is not handled properly. Fix it by falling back to B9600 in this case.

Signed-off-by: David Müller <d.mueller@elsoft.ch>
Fixes: 21947ba654a6 ("serial: 8250_pci: replace switch-case by formula")
Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/tty/serial/8250/8250_pci.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/tty/serial/8250/8250_pci.c
+++ b/drivers/tty/serial/8250/8250_pci.c
@@ -1401,6 +1401,9 @@ byt_set_termios(struct uart_port *p, str
 	unsigned long m, n;
 	u32 reg;
 
+	/* Gracefully handle the B0 case: fall back to B9600 */
+	fuart = fuart ? fuart : 9600 * 16;
+
 	/* Get Fuart closer to Fref */
 	fuart *= rounddown_pow_of_two(fref / fuart);
 


Patches currently in stable-queue which might be from d.mueller@elsoft.ch are

queue-4.4/serial-8250_pci-fix-divide-error-bug-if-baud-rate-is-0.patch