[GIT PATCH] Fix memory leak in qcserial driver

Steven Hardy
2011-03-28T14:06:33Z

Hi,

I've been experimenting with kmemleak and noticed a recurring leak warning whenever I load & unload the qcserial driver.

Inspection of the code seems to indicate the leak is the serial->private data allocated in the qcprobe() function,
which is never freed (apart from in some of the qcprobe error paths) as far as I can tell.

The patch below fixes the following problems:
1 - Always free the serial->private data allocated in qcprobe, added a new function qc_release which frees the memory rather
than relying on the usb_wwan_release function which does not. Without this cleanup, we leak the memory allocated in qcprobe
when the kfree(serial) happens in usb-serial.c::destroy_serial()

2 - Ensure that the serial->private data is freed in the event of the probe failing and returning -ENODEV.
This error-path leak is less likely but still possible, it was discussed previously but not actually fixed AFAICS:
http://kerneltrap.org/mailarchive/linux-kernel/2010/6/14/4582980/thread,
http://lkml.org/lkml/2010/6/20/234

3 - Don't assign serial->private when doing the kzalloc or serial->private ends up pointing to freed memory in the event we return -ENODEV,
instead call usb_set_serial_data(serial, data) at the end of the function, and only have one return.

Please keep me on CC for any responses or review comments, since I'm not currently subscribed to LKML

Signed-off-by: Steve Hardy <shardy@redhat.com>

diff --git a/drivers/usb/serial/qcserial.c b/drivers/usb/serial/qcserial.c
index 8858201..e66530a 100644
--- a/drivers/usb/serial/qcserial.c
+++ b/drivers/usb/serial/qcserial.c
@@ -111,7 +111,7 @@ static int qcprobe(struct usb_serial *serial, const struct usb_device_id *id)
ifnum = intf->desc.bInterfaceNumber;
dbg("This Interface = %d", ifnum);

- data = serial->private = kzalloc(sizeof(struct usb_wwan_intf_private),
+ data = kzalloc(sizeof(struct usb_wwan_intf_private),
GFP_KERNEL);
if (!data)
return -ENOMEM;
@@ -134,8 +134,10 @@ static int qcprobe(struct usb_serial *serial, const struct usb_device_id *id)
usb_endpoint_is_bulk_out(&intf->endpoint[1].desc)) {
dbg("QDL port found");

- if (serial->interface->num_altsetting == 1)
- return 0;
+ if (serial->interface->num_altsetting == 1) {
+ retval = 0; /* Success */
+ break;
+ }

retval = usb_set_interface(serial->dev, ifnum, 1);
if (retval < 0) {
@@ -145,7 +147,6 @@ static int qcprobe(struct usb_serial *serial, const struct usb_device_id *id)
retval = -ENODEV;
kfree(data);
}
- return retval;
}
break;

@@ -166,6 +167,7 @@ static int qcprobe(struct usb_serial *serial, const struct usb_device_id *id)
"Could not set interface, error %d\n",
retval);
retval = -ENODEV;
+ kfree(data);
}
} else if (ifnum == 2) {
dbg("Modem port found");
@@ -177,7 +179,6 @@ static int qcprobe(struct usb_serial *serial, const struct usb_device_id *id)
retval = -ENODEV;
kfree(data);
}
- return retval;
} else if (ifnum==3) {
/*
* NMEA (serial line 9600 8N1)
@@ -191,6 +192,7 @@ static int qcprobe(struct usb_serial *serial, const struct usb_device_id *id)
"Could not set interface, error %d\n",
retval);
retval = -ENODEV;
+ kfree(data);
}
}
break;
@@ -198,13 +200,27 @@ static int qcprobe(struct usb_serial *serial, const struct usb_device_id *id)
default:
dev_err(&serial->dev->dev,
"unknown number of interfaces: %d\n", nintf);
+ retval = -ENODEV;
kfree(data);
- return -ENODEV;
}

+ /* Set serial->private may be null if -ENODEV */
+ usb_set_serial_data(serial, data);
return retval;
}

+static void qc_release(struct usb_serial *serial)
+{
+ struct usb_wwan_intf_private *priv = usb_get_serial_data(serial);
+
+ dbg("%s", __func__);
+
+ /* Call usb_wwan release & free the private data allocated in qcprobe */
+ usb_wwan_release(serial);
+ usb_set_serial_data(serial, NULL);
+ kfree(priv);
+}
+
static struct usb_serial_driver qcdevice = {
.driver = {
.owner = THIS_MODULE,
@@ -222,7 +238,7 @@ static struct usb_serial_driver qcdevice = {
.chars_in_buffer = usb_wwan_chars_in_buffer,
.attach = usb_wwan_startup,
.disconnect = usb_wwan_disconnect,
- .release = usb_wwan_release,
+ .release = qc_release,
#ifdef CONFIG_PM
.suspend = usb_wwan_suspend,
.resume = usb_wwan_resume,