[ 3.8.y.z extended stable ] Patch "USB: mos7840: fix race in register handling" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    USB: mos7840: fix race in register handling

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.7.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From c9fdbc5790cf3f9877500b8790e0dc092f96c31e Mon Sep 17 00:00:00 2001
From: Johan Hovold <jhovold at gmail.com>
Date: Fri, 26 Jul 2013 11:55:17 +0200
Subject: USB: mos7840: fix race in register handling

commit d8a083cc746664916d9d36ed9e4d08a29525f245 upstream.

Fix race in mos7840_get_reg which unconditionally manipulated the
control urb (which may already be in use) by adding a control-urb busy
flag.

Signed-off-by: Johan Hovold <jhovold at gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/usb/serial/mos7840.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/serial/mos7840.c b/drivers/usb/serial/mos7840.c
index 06ca54a..eab52f6 100644
--- a/drivers/usb/serial/mos7840.c
+++ b/drivers/usb/serial/mos7840.c
@@ -183,6 +183,10 @@
 #define LED_ON_MS	500
 #define LED_OFF_MS	500

+enum mos7840_flag {
+	MOS7840_FLAG_CTRL_BUSY,
+};
+
 static int device_type;

 static const struct usb_device_id id_table[] = {
@@ -243,6 +247,8 @@ struct moschip_port {
 	bool led_flag;
 	struct timer_list led_timer1;	/* Timer for LED on */
 	struct timer_list led_timer2;	/* Timer for LED off */
+
+	unsigned long flags;
 };

 /*
@@ -487,10 +493,10 @@ static void mos7840_control_callback(struct urb *urb)
 	case -ESHUTDOWN:
 		/* this urb is terminated, clean up */
 		dev_dbg(dev, "%s - urb shutting down with status: %d\n", __func__, status);
-		return;
+		goto out;
 	default:
 		dev_dbg(dev, "%s - nonzero urb status received: %d\n", __func__, status);
-		return;
+		goto out;
 	}

 	dev_dbg(dev, "%s urb buffer size is %d\n", __func__, urb->actual_length);
@@ -503,6 +509,8 @@ static void mos7840_control_callback(struct urb *urb)
 		mos7840_handle_new_msr(mos7840_port, regval);
 	else if (mos7840_port->MsrLsr == 1)
 		mos7840_handle_new_lsr(mos7840_port, regval);
+out:
+	clear_bit_unlock(MOS7840_FLAG_CTRL_BUSY, &mos7840_port->flags);
 }

 static int mos7840_get_reg(struct moschip_port *mcs, __u16 Wval, __u16 reg,
@@ -513,6 +521,9 @@ static int mos7840_get_reg(struct moschip_port *mcs, __u16 Wval, __u16 reg,
 	unsigned char *buffer = mcs->ctrl_buf;
 	int ret;

+	if (test_and_set_bit_lock(MOS7840_FLAG_CTRL_BUSY, &mcs->flags))
+		return -EBUSY;
+
 	dr->bRequestType = MCS_RD_RTYPE;
 	dr->bRequest = MCS_RDREQ;
 	dr->wValue = cpu_to_le16(Wval);	/* 0 */
@@ -524,6 +535,9 @@ static int mos7840_get_reg(struct moschip_port *mcs, __u16 Wval, __u16 reg,
 			     mos7840_control_callback, mcs);
 	mcs->control_urb->transfer_buffer_length = 2;
 	ret = usb_submit_urb(mcs->control_urb, GFP_ATOMIC);
+	if (ret)
+		clear_bit_unlock(MOS7840_FLAG_CTRL_BUSY, &mcs->flags);
+
 	return ret;
 }

--
1.8.1.2