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: Marcel Selhorst <tpm@selhorst.net>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 27 insertions, 17 deletions

diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c
index c88424a0c89b..a5d8bcb40000 100644
--- a/drivers/char/tpm/tpm.c
+++ b/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);
 
@@ -1083,6 +1078,26 @@ 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
  * this function the specific probe function has called pci_enable_device
@@ -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;
         }