Re: [PATCH] [DRIVER MODEL] Fix macsonic

[Russell King <rmk+lkml@arm.linux.org.uk>]

Release code in driver modules is a potential cause of oopsen.
The device may be in use by a userspace process, which will keep
a reference to the device.  If the module is unloaded, the module
text will be freed.  Subsequently, when the last reference is
dropped, the release code will be called, which no longer exists.

Use generic platform device allocation/release code in modules.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --git a/drivers/net/macsonic.c b/drivers/net/macsonic.c
--- a/drivers/net/macsonic.c
+++ b/drivers/net/macsonic.c
@@ -599,18 +599,8 @@ static struct device_driver mac_sonic_dr
 	.remove = __devexit_p(mac_sonic_device_remove),
 };
 
-static void mac_sonic_platform_release(struct device *device)
-{
-	struct platform_device *pldev;
-
-	/* free device */
-	pldev = to_platform_device (device);
-	kfree (pldev);
-}
-
 static int __init mac_sonic_init_module(void)
 {
-	struct platform_device *pldev;
 	int err;
 
 	if ((err = driver_register(&mac_sonic_driver))) {
@@ -618,27 +608,20 @@ static int __init mac_sonic_init_module(
 		return err;
 	}
 
-	mac_sonic_device = NULL;
-
-	if (!(pldev = kmalloc (sizeof (*pldev), GFP_KERNEL))) {
+	mac_sonic_device = platform_device_alloc(mac_sonic_string, 0);
+	if (!mac_sonic_device) {
 		goto out_unregister;
 	}
 
-	memset(pldev, 0, sizeof (*pldev));
-	pldev->name		= mac_sonic_string;
-	pldev->id		= 0;
-	pldev->dev.release	= mac_sonic_platform_release;
-	mac_sonic_device	= pldev;
-
-	if (platform_device_register (pldev)) {
-		kfree(pldev);
+	if (platform_device_add(mac_sonic_device)) {
+		platform_device_put(mac_sonic_device);
 		mac_sonic_device = NULL;
 	}
 
 	return 0;
 
 out_unregister:
-	platform_device_unregister(pldev);
+	driver_unregister(&mac_sonic_driver);
 
 	return -ENOMEM;
 }


-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 Serial core