tpm: Issue a TPM2_Shutdown for TPM2 devices.

commit d1bd4a792d3961a04e6154118816b00167aad91a upstream.

If a TPM2 loses power without a TPM2_Shutdown command being issued (a
"disorderly reboot"), it may lose some state that has yet to be
persisted to NVRam, and will increment the DA counter. After the DA
counter gets sufficiently large, the TPM will lock the user out.

NOTE: This only changes behavior on TPM2 devices. Since TPM1 uses sysfs,
and sysfs relies on implicit locking on chip->ops, it is not safe to
allow this code to run in TPM1, or to add sysfs support to TPM2, until
that locking is made explicit.

Signed-off-by: Josh Zimmerman <joshz@google.com>
Fixes: 74d6b3ceaa17 ("tpm: fix suspend/resume paths for TPM 2.0")
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index c406343848dac66223da77c901342da362a12d1b..5aa1146921d1a551aa95bc99271e79ed67526e63 100644 (file)
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -131,6 +131,39 @@ static void tpm_dev_release(struct device *dev)
        kfree(chip);
 }
 
+/**
+ * tpm_class_shutdown() - prepare the TPM device for loss of power.
+ * @dev: device to which the chip is associated.
+ *
+ * Issues a TPM2_Shutdown command prior to loss of power, as required by the
+ * TPM 2.0 spec.
+ * Then, calls bus- and device- specific shutdown code.
+ *
+ * XXX: This codepath relies on the fact that sysfs is not enabled for
+ * TPM2: sysfs uses an implicit lock on chip->ops, so this could race if TPM2
+ * has sysfs support enabled before TPM sysfs's implicit locking is fixed.
+ */
+static int tpm_class_shutdown(struct device *dev)
+{
+       struct tpm_chip *chip = container_of(dev, struct tpm_chip, dev);
+
+       if (chip->flags & TPM_CHIP_FLAG_TPM2) {
+               down_write(&chip->ops_sem);
+               tpm2_shutdown(chip, TPM2_SU_CLEAR);
+               chip->ops = NULL;
+               up_write(&chip->ops_sem);
+       }
+       /* Allow bus- and device-specific code to run. Note: since chip->ops
+        * is NULL, more-specific shutdown code will not be able to issue TPM
+        * commands.
+        */
+       if (dev->bus && dev->bus->shutdown)
+               dev->bus->shutdown(dev);
+       else if (dev->driver && dev->driver->shutdown)
+               dev->driver->shutdown(dev);
+       return 0;
+}
+
 /**
  * tpm_chip_alloc() - allocate a new struct tpm_chip instance
  * @pdev: device to which the chip is associated
@@ -169,6 +202,7 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
        device_initialize(&chip->dev);
 
        chip->dev.class = tpm_class;
+       chip->dev.class->shutdown = tpm_class_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 2f596d74f80c4e9a9a0d27a644b885407a76fbf4..c7aa18f66627e4d7d3c979b853fb049e110a8a96 100644 (file)
--- a/drivers/char/tpm/tpm-sysfs.c
+++ b/drivers/char/tpm/tpm-sysfs.c
@@ -294,6 +294,9 @@ static const struct attribute_group tpm_dev_group = {
 
 void tpm_sysfs_add_device(struct tpm_chip *chip)
 {
+       /* XXX: If you wish to remove this restriction, you must first update
+        * tpm_sysfs to explicitly lock chip->ops.
+        */
        if (chip->flags & TPM_CHIP_FLAG_TPM2)
                return;