releases/2.6.20.2/usb-fix-concurrent-buffer-access-in-the-hub-driver.patch

From stable-bounces@linux.kernel.org Mon Feb  5 06:57:55 2007
From: Alan Stern <stern@rowland.harvard.edu>
Date: Mon, 5 Feb 2007 09:56:15 -0500 (EST)
Subject: USB: fix concurrent buffer access in the hub driver
To: Greg KH <greg@kroah.com>
Cc: stable@kernel.org, USB development list <linux-usb-devel@lists.sourceforge.net>, Adrian Bunk <bunk@stusta.de>
Message-ID: <Pine.LNX.4.44L0.0702050950390.3533-100000@iolanthe.rowland.org>


This patch (as849) fixes a bug in the USB hub driver.  A single
pre-allocated buffer is used for all port status reads, but nothing
guarantees exclusive use of the buffer.  A mutex is added to provide
this guarantee.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 drivers/usb/core/hub.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- linux-2.6.20.1.orig/drivers/usb/core/hub.c
+++ linux-2.6.20.1/drivers/usb/core/hub.c
@@ -44,6 +44,7 @@ struct usb_hub {
 		struct usb_hub_status	hub;
 		struct usb_port_status	port;
 	}			*status;	/* buffer for status reports */
+	struct mutex		status_mutex;	/* for the status buffer */
 
 	int			error;		/* last reported error */
 	int			nerrors;	/* track consecutive errors */
@@ -538,6 +539,7 @@ static int hub_hub_status(struct usb_hub
 {
 	int ret;
 
+	mutex_lock(&hub->status_mutex);
 	ret = get_hub_status(hub->hdev, &hub->status->hub);
 	if (ret < 0)
 		dev_err (hub->intfdev,
@@ -547,6 +549,7 @@ static int hub_hub_status(struct usb_hub
 		*change = le16_to_cpu(hub->status->hub.wHubChange); 
 		ret = 0;
 	}
+	mutex_unlock(&hub->status_mutex);
 	return ret;
 }
 
@@ -620,6 +623,7 @@ static int hub_configure(struct usb_hub 
 		ret = -ENOMEM;
 		goto fail;
 	}
+	mutex_init(&hub->status_mutex);
 
 	hub->descriptor = kmalloc(sizeof(*hub->descriptor), GFP_KERNEL);
 	if (!hub->descriptor) {
@@ -1418,6 +1422,7 @@ static int hub_port_status(struct usb_hu
 {
 	int ret;
 
+	mutex_lock(&hub->status_mutex);
 	ret = get_port_status(hub->hdev, port1, &hub->status->port);
 	if (ret < 4) {
 		dev_err (hub->intfdev,
@@ -1429,6 +1434,7 @@ static int hub_port_status(struct usb_hu
 		*change = le16_to_cpu(hub->status->port.wPortChange); 
 		ret = 0;
 	}
+	mutex_unlock(&hub->status_mutex);
 	return ret;
 }