[PATCH] tpm: Issue a TPM2_Shutdown for TPM2 devices.

[Josh Zimmerman <joshz-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>]

If a TPM2 loses power without a TPM2_Shutdown command being issued, it
may lose some state that has yet to be persisted to NVRam, and will
increment the DA counter (meaning that after too many disorderly
reboots, the TPM will lock the user out).

This is a variant of https://patchwork.kernel.org/patch/9516631/.
It differs in that:
  * It only changes behavior on TPM2 devices, to avoid invoking the
  unbounded-waiting sysfs codepath that was discussed on that patch, and
  to avoid racing on chip->ops.
  * It modifies tpm-chip rather than tpm_i2c_infineon, so that it can
  change behavior for all TPM2 devices.

This patch is dependent on '[PATCH] Add "shutdown" to "struct class".'
http://marc.info/?l=linux-kernel&m=149463235025420&w=2

Signed-off-by: Josh Zimmerman <joshz-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
---
 drivers/base/core.c          |  5 +++++
 drivers/char/tpm/tpm-chip.c  | 19 +++++++++++++++++++
 drivers/char/tpm/tpm-sysfs.c |  2 ++
 include/linux/device.h       |  4 +++-
 4 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 6bb60fb6a30b..687668d9afbe 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -2667,6 +2667,11 @@ void device_shutdown(void)
 		pm_runtime_get_noresume(dev);
 		pm_runtime_barrier(dev);
 
+		if (dev->class && dev->class->shutdown) {
+			if (initcall_debug)
+				dev_info(dev, "shutdown\n");
+			dev->class->shutdown(dev);
+		}
 		if (dev->bus && dev->bus->shutdown) {
 			if (initcall_debug)
 				dev_info(dev, "shutdown\n");
diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index 9dec9f551b83..024dadc0a829 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -142,6 +142,24 @@ static void tpm_devs_release(struct device *dev)
 	put_device(&chip->dev);
 }
 
+static void tpm_shutdown(struct device *dev)
+{
+	struct tpm_chip *chip = container_of(dev, struct tpm_chip, dev);
+	// TPM 2.0 requires that the TPM2_Shutdown() command be issued prior to
+	// loss of power. If it is not, the DA counter will be incremented and,
+	// eventually, the user will be locked out of their TPM.
+	// XXX: This codepath relies on the fact that sysfs is not enabled for
+	// TPM2: sysfs uses an implicit lock on chip->ops, so this use could
+	// race if TPM2 has sysfs support enabled before TPM sysfs's implicit
+	// locking is fixed.
+	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
+		down_read(&chip->ops_sem);
+		tpm2_shutdown(chip, TPM_SU_CLEAR);
+		chip->ops = NULL;
+		up_read(&chip->ops_sem);
+	}
+}
+
 /**
  * tpm_chip_alloc() - allocate a new struct tpm_chip instance
  * @pdev: device to which the chip is associated
@@ -181,6 +199,7 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
 	device_initialize(&chip->devs);
 
 	chip->dev.class = tpm_class;
+	chip->dev.class.shutdown = tpm_shutdown;
 	chip->dev.release = tpm_dev_release;
 	chip->dev.parent = pdev;
 	chip->dev.groups = chip->groups;
diff --git a/drivers/char/tpm/tpm-sysfs.c b/drivers/char/tpm/tpm-sysfs.c
index 55405dbe43fa..6256f6e174b0 100644
--- a/drivers/char/tpm/tpm-sysfs.c
+++ b/drivers/char/tpm/tpm-sysfs.c
@@ -294,6 +294,8 @@ static const struct attribute_group tpm_dev_group = {
 
 void tpm_sysfs_add_device(struct tpm_chip *chip)
 {
+	// XXX: Before this restriction is removed, tpm_sysfs must be updated
+	// to explicitly lock chip->ops.
 	if (chip->flags & TPM_CHIP_FLAG_TPM2)
 		return;
 
diff --git a/include/linux/device.h b/include/linux/device.h
index 9ef518af5515..a150f8d3b3f1 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -378,6 +378,7 @@ int subsys_virtual_register(struct bus_type *subsys,
  * @suspend:	Used to put the device to sleep mode, usually to a low power
  *		state.
  * @resume:	Used to bring the device from the sleep mode.
+ * @shutdown:	Called at shut-down time to quiesce the device.
  * @ns_type:	Callbacks so sysfs can detemine namespaces.
  * @namespace:	Namespace of the device belongs to this class.
  * @pm:		The default device power management operations of this class.
@@ -407,6 +408,7 @@ struct class {
 
 	int (*suspend)(struct device *dev, pm_message_t state);
 	int (*resume)(struct device *dev);
+	int (*shutdown)(struct device *dev);
 
 	const struct kobj_ns_type_operations *ns_type;
 	const void *(*namespace)(struct device *dev);
@@ -1228,7 +1230,7 @@ static inline int devtmpfs_delete_node(struct device *dev) { return 0; }
 static inline int devtmpfs_mount(const char *mountpoint) { return 0; }
 #endif
 
-/* drivers/base/power/shutdown.c */
+/* drivers/base/core.c */
 extern void device_shutdown(void);
 
 /* debugging and troubleshooting/diagnostic helpers. */
-- 
2.13.0.rc2.291.g57267f2277-goog


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