USB: fix concurrent buffer access in the hub driver

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>

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 7d60065..50c0db1 100644 (file)
--- a/drivers/usb/core/hub.c
+++ b/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 */
@@ -535,6 +536,7 @@ static int hub_hub_status(struct usb_hub *hub,
 {
        int ret;
 
+       mutex_lock(&hub->status_mutex);
        ret = get_hub_status(hub->hdev, &hub->status->hub);
        if (ret < 0)
                dev_err (hub->intfdev,
@@ -544,6 +546,7 @@ static int hub_hub_status(struct usb_hub *hub,
                *change = le16_to_cpu(hub->status->hub.wHubChange); 
                ret = 0;
        }
+       mutex_unlock(&hub->status_mutex);
        return ret;
 }
 
@@ -617,6 +620,7 @@ static int hub_configure(struct usb_hub *hub,
                ret = -ENOMEM;
                goto fail;
        }
+       mutex_init(&hub->status_mutex);
 
        hub->descriptor = kmalloc(sizeof(*hub->descriptor), GFP_KERNEL);
        if (!hub->descriptor) {
@@ -1396,6 +1400,7 @@ static int hub_port_status(struct usb_hub *hub, int port1,
 {
        int ret;
 
+       mutex_lock(&hub->status_mutex);
        ret = get_port_status(hub->hdev, port1, &hub->status->port);
        if (ret < 4) {
                dev_err (hub->intfdev,
@@ -1407,6 +1412,7 @@ static int hub_port_status(struct usb_hub *hub, int port1,
                *change = le16_to_cpu(hub->status->port.wPortChange); 
                ret = 0;
        }
+       mutex_unlock(&hub->status_mutex);
        return ret;
 }