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Subject[patch 013/101] 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>

---
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;
}

--
-
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