From: Andi Kleen <ak@xxxxxxxxxxxxxxx>
The usb serial driver initialization tried to use the BKL to stop
driver modules from unloading, but that didn't work anyways.
There was already some code to do proper try_module_get,
but it was conditional on having a new probe interface.
I checked all the low level drivers and they all have proper
.owner = THIS_MODULE, so it's ok to always use.
The other problem was the usb_serial_driver_list needing
protection by a lock. This was broken anyways because unregister
did not necessarily have the BKL.
I extended the extending table_lock mutex to protect this case too.
With these changes the BKL can be removed here.
Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
---
drivers/usb/serial/usb-serial.c | 30 ++++++++++++++----------------
1 files changed, 14 insertions(+), 16 deletions(-)
diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c
index 941c2d4..443468e 100644
--- a/drivers/usb/serial/usb-serial.c
+++ b/drivers/usb/serial/usb-serial.c
@@ -653,6 +653,7 @@ exit:
return id;
}
+/* Caller must hold table_lock */
static struct usb_serial_driver *search_serial_device(
struct usb_interface *iface)
{
@@ -718,17 +719,23 @@ int usb_serial_probe(struct usb_interface *interface,
int num_ports = 0;
int max_endpoints;
- lock_kernel(); /* guard against unloading a serial driver module */
+ mutex_lock(&table_lock);
type = search_serial_device(interface);
if (!type) {
- unlock_kernel();
+ mutex_unlock(&table_lock);
dbg("none matched");
return -ENODEV;
}
+ if (!try_module_get(type->driver.owner)) {
+ mutex_unlock(&table_lock);
+ dev_err(&interface->dev, "module get failed, exiting\n");
+ return -EIO;
+ }
+ mutex_unlock(&table_lock);
+
serial = create_serial(dev, interface, type);
if (!serial) {
- unlock_kernel();
dev_err(&interface->dev, "%s - out of memory\n", __func__);
return -ENOMEM;
}
@@ -737,20 +744,11 @@ int usb_serial_probe(struct usb_interface *interface,
if (type->probe) {
const struct usb_device_id *id;
- if (!try_module_get(type->driver.owner)) {
- unlock_kernel();
- dev_err(&interface->dev,
- "module get failed, exiting\n");
- kfree(serial);
- return -EIO;
- }
-
id = get_iface_id(type, interface);
retval = type->probe(serial, id);
module_put(type->driver.owner);
if (retval) {
- unlock_kernel();
dbg("sub driver rejected device");
kfree(serial);
return retval;
@@ -822,7 +820,6 @@ int usb_serial_probe(struct usb_interface *interface,
* properly during a later invocation of usb_serial_probe
*/
if (num_bulk_in == 0 || num_bulk_out == 0) {
- unlock_kernel();
dev_info(&interface->dev, "PL-2303 hack: descriptors matched but endpoints did not\n");
kfree(serial);
return -ENODEV;
@@ -835,7 +832,6 @@ int usb_serial_probe(struct usb_interface *interface,
if (type == &usb_serial_generic_device) {
num_ports = num_bulk_out;
if (num_ports == 0) {
- unlock_kernel();
dev_err(&interface->dev,
"Generic device with no bulk out, not allowed.\n");
kfree(serial);
@@ -847,7 +843,6 @@ int usb_serial_probe(struct usb_interface *interface,
/* if this device type has a calc_num_ports function, call it */
if (type->calc_num_ports) {
if (!try_module_get(type->driver.owner)) {
- unlock_kernel();
dev_err(&interface->dev,
"module get failed, exiting\n");
kfree(serial);
@@ -878,7 +873,6 @@ int usb_serial_probe(struct usb_interface *interface,
max_endpoints = max(max_endpoints, num_interrupt_out);
max_endpoints = max(max_endpoints, (int)serial->num_ports);
serial->num_port_pointers = max_endpoints;
- unlock_kernel();
dbg("%s - setting up %d port structures for this device",
__func__, max_endpoints);
@@ -1349,6 +1343,7 @@ int usb_serial_register(struct usb_serial_driver *driver)
driver->description = driver->driver.name;
/* Add this device to our list of devices */
+ mutex_lock(&table_lock);
list_add(&driver->driver_list, &usb_serial_driver_list);
retval = usb_serial_bus_register(driver);
@@ -1360,6 +1355,7 @@ int usb_serial_register(struct usb_serial_driver *driver)
printk(KERN_INFO "USB Serial support registered for %s\n",
driver->description);
+ mutex_unlock(&table_lock);
return retval;
}
EXPORT_SYMBOL_GPL(usb_serial_register);
@@ -1370,8 +1366,10 @@ void usb_serial_deregister(struct usb_serial_driver *device)
/* must be called with BKL held */
printk(KERN_INFO "USB Serial deregistering driver %s\n",
device->description);
+ mutex_lock(&table_lock);
list_del(&device->driver_list);
usb_serial_bus_deregister(device);
+ mutex_unlock(&table_lock);
}
EXPORT_SYMBOL_GPL(usb_serial_deregister);
--
1.7.2
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