tpm.c: fix crash during device removal

The clean up procedure now uses platform device "release" callback to
handle memory clean up.  For this purpose "release" function callback was
added to struct tpm_vendor_specific, so hw device driver provider can get
called when it is safe to remove all allocated resources.

This is supposed to fix a bug in device removal, where device while in
receive function (waiting on timeout) was prone to segfault, if the
tpm_chip struct was unallocated before the timeout expired (in
tpm_remove_hardware).
Acked-by: NMarcel Selhorst <tpm@selhorst.net>
Cc: <stable@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/char/tpm/tpm.c

@@ -1031,18 +1031,13 @@ void tpm_remove_hardware(struct device *dev)
 
 	spin_unlock(&driver_lock);
 
-	dev_set_drvdata(dev, NULL);
 	misc_deregister(&chip->vendor.miscdev);
-	kfree(chip->vendor.miscdev.name);
 
 	sysfs_remove_group(&dev->kobj, chip->vendor.attr_group);
 	tpm_bios_log_teardown(chip->bios_dir);
 
-	clear_bit(chip->dev_num, dev_mask);
-
-	kfree(chip);
-
-	put_device(dev);
+	/* write it this way to be explicit (chip->dev == dev) */
+	put_device(chip->dev);
 }
 EXPORT_SYMBOL_GPL(tpm_remove_hardware);
 
@@ -1082,6 +1077,26 @@ int tpm_pm_resume(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(tpm_pm_resume);
 
+/*
+ * Once all references to platform device are down to 0,
+ * release all allocated structures.
+ * In case vendor provided release function,
+ * call it too.
+ */
+static void tpm_dev_release(struct device *dev)
+{
+	struct tpm_chip *chip = dev_get_drvdata(dev);
+
+	if (chip->vendor.release)
+		chip->vendor.release(dev);
+
+	chip->release(dev);
+
+	clear_bit(chip->dev_num, dev_mask);
+	kfree(chip->vendor.miscdev.name);
+	kfree(chip);
+}
+
 /*
  * Called from tpm_<specific>.c probe function only for devices 
  * the driver has determined it should claim.  Prior to calling
@@ -1136,23 +1151,21 @@ struct tpm_chip *tpm_register_hardware(struct device *dev, const struct tpm_vend
 
 	chip->vendor.miscdev.parent = dev;
 	chip->dev = get_device(dev);
+	chip->release = dev->release;
+	dev->release = tpm_dev_release;
+	dev_set_drvdata(dev, chip);
 
 	if (misc_register(&chip->vendor.miscdev)) {
 		dev_err(chip->dev,
 			"unable to misc_register %s, minor %d\n",
 			chip->vendor.miscdev.name,
 			chip->vendor.miscdev.minor);
-		put_device(dev);
-		clear_bit(chip->dev_num, dev_mask);
-		kfree(chip);
-		kfree(devname);
+		put_device(chip->dev);
 		return NULL;
 	}
 
 	spin_lock(&driver_lock);
 
-	dev_set_drvdata(dev, chip);
-
 	list_add(&chip->list, &tpm_chip_list);
 
 	spin_unlock(&driver_lock);
@@ -1160,10 +1173,7 @@ struct tpm_chip *tpm_register_hardware(struct device *dev, const struct tpm_vend
 	if (sysfs_create_group(&dev->kobj, chip->vendor.attr_group)) {
 		list_del(&chip->list);
 		misc_deregister(&chip->vendor.miscdev);
-		put_device(dev);
-		clear_bit(chip->dev_num, dev_mask);
-		kfree(chip);
-		kfree(devname);
+		put_device(chip->dev);
 		return NULL;
 	}
 

drivers/char/tpm/tpm.h

@@ -74,6 +74,7 @@ struct tpm_vendor_specific {
 	int (*send) (struct tpm_chip *, u8 *, size_t);
 	void (*cancel) (struct tpm_chip *);
 	u8 (*status) (struct tpm_chip *);
+	void (*release) (struct device *);
 	struct miscdevice miscdev;
 	struct attribute_group *attr_group;
 	struct list_head list;
@@ -106,6 +107,7 @@ struct tpm_chip {
 	struct dentry **bios_dir;
 
 	struct list_head list;
+	void (*release) (struct device *);
 };
 
 #define to_tpm_chip(n) container_of(n, struct tpm_chip, vendor)