[PATCH RFC v4 5/5] tpm2: expose spaces via a device link /dev/tpms

Jarkko Sakkinen
2017-01-22T23:45:11Z

From: James Bottomley <James.Bottomley@HansenPartnership.com>

Currently the tpm spaces are not exposed to userspace. Make this
exposure via a separate device, which can now be opened multiple times
because each read/write transaction goes separately via the space.

Concurrency is protected by the chip->tpm_mutex for each read/write
transaction separately. The TPM is cleared of all transient objects
by the time the mutex is dropped, so there should be no interference
between the kernel and userspace.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
drivers/char/tpm/Makefile | 2 +-
drivers/char/tpm/tpm-chip.c | 71 ++++++++++++++++++++++++++++++++++++++--
drivers/char/tpm/tpm-interface.c | 13 ++++++--
drivers/char/tpm/tpm.h | 4 +++
drivers/char/tpm/tpms-dev.c | 65 ++++++++++++++++++++++++++++++++++++
5 files changed, 149 insertions(+), 6 deletions(-)
create mode 100644 drivers/char/tpm/tpms-dev.c

diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
index 13ff5da..e50d768 100644
--- a/drivers/char/tpm/Makefile
+++ b/drivers/char/tpm/Makefile
@@ -3,7 +3,7 @@
#
obj-$(CONFIG_TCG_TPM) += tpm.o
tpm-y := tpm-interface.o tpm-dev.o tpm-sysfs.o tpm-chip.o tpm2-cmd.o \
- tpm_eventlog.o tpm2-space.o tpm-dev-common.o
+ tpm_eventlog.o tpm2-space.o tpm-dev-common.o tpms-dev.o
tpm-$(CONFIG_ACPI) += tpm_ppi.o tpm_acpi.o
tpm-$(CONFIG_OF) += tpm_of.o
obj-$(CONFIG_TCG_TIS_CORE) += tpm_tis_core.o
diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index 993b9ae..ed4f887 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -33,6 +33,7 @@ DEFINE_IDR(dev_nums_idr);
static DEFINE_MUTEX(idr_lock);

struct class *tpm_class;
+struct class *tpms_class;
dev_t tpm_devt;

/**
@@ -132,6 +133,14 @@ static void tpm_dev_release(struct device *dev)
kfree(chip);
}

+static void tpm_devs_release(struct device *dev)
+{
+ struct tpm_chip *chip = container_of(dev, struct tpm_chip, devs);
+
+ /* release the master device reference */
+ put_device(&chip->dev);
+}
+
/**
* tpm_chip_alloc() - allocate a new struct tpm_chip instance
* @pdev: device to which the chip is associated
@@ -168,27 +177,46 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
chip->dev_num = rc;

device_initialize(&chip->dev);
+ device_initialize(&chip->devs);

chip->dev.class = tpm_class;
chip->dev.release = tpm_dev_release;
chip->dev.parent = pdev;
chip->dev.groups = chip->groups;

+ chip->devs.parent = pdev;
+ chip->devs.class = tpms_class;
+ chip->devs.release = tpm_devs_release;
+ /* get extra reference on main device to hold on
+ * behalf of devs. This holds the chip structure
+ * while cdevs is in use. The corresponding put
+ * is in the tpm_devs_release */
+ get_device(&chip->dev);
+
if (chip->dev_num == 0)
chip->dev.devt = MKDEV(MISC_MAJOR, TPM_MINOR);
else
chip->dev.devt = MKDEV(MAJOR(tpm_devt), chip->dev_num);

+ chip->devs.devt =
+ MKDEV(MAJOR(tpm_devt), chip->dev_num + TPM_NUM_DEVICES);
+
rc = dev_set_name(&chip->dev, "tpm%d", chip->dev_num);
if (rc)
goto out;
+ rc = dev_set_name(&chip->devs, "tpms%d", chip->dev_num);
+ if (rc)
+ goto out;

if (!pdev)
chip->flags |= TPM_CHIP_FLAG_VIRTUAL;

cdev_init(&chip->cdev, &tpm_fops);
+ cdev_init(&chip->cdevs, &tpms_fops);
chip->cdev.owner = THIS_MODULE;
+ chip->cdevs.owner = THIS_MODULE;
chip->cdev.kobj.parent = &chip->dev.kobj;
+ chip->cdevs.kobj.parent = &chip->devs.kobj;

chip->work_space.context_buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
if (!chip->work_space.context_buf) {
@@ -199,6 +227,7 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
return chip;

out:
+ put_device(&chip->devs);
put_device(&chip->dev);
return ERR_PTR(rc);
}
@@ -244,7 +273,7 @@ static int tpm_add_char_device(struct tpm_chip *chip)
dev_name(&chip->dev), MAJOR(chip->dev.devt),
MINOR(chip->dev.devt), rc);

- return rc;
+ goto err_1;
}

rc = device_add(&chip->dev);
@@ -254,16 +283,44 @@ static int tpm_add_char_device(struct tpm_chip *chip)
dev_name(&chip->dev), MAJOR(chip->dev.devt),
MINOR(chip->dev.devt), rc);

- cdev_del(&chip->cdev);
- return rc;
+ goto err_2;
+ }
+
+ if (chip->flags & TPM_CHIP_FLAG_TPM2)
+ rc = cdev_add(&chip->cdevs, chip->devs.devt, 1);
+ if (rc) {
+ dev_err(&chip->dev,
+ "unable to cdev_add() %s, major %d, minor %d, err=%d\n",
+ dev_name(&chip->devs), MAJOR(chip->devs.devt),
+ MINOR(chip->devs.devt), rc);
+
+ goto err_3;
}

+ if (chip->flags & TPM_CHIP_FLAG_TPM2)
+ rc = device_add(&chip->devs);
+ if (rc) {
+ dev_err(&chip->dev,
+ "unable to device_register() %s, major %d, minor %d, err=%d\n",
+ dev_name(&chip->devs), MAJOR(chip->devs.devt),
+ MINOR(chip->devs.devt), rc);
+
+ goto err_4;
+ }
/* Make the chip available. */
mutex_lock(&idr_lock);
idr_replace(&dev_nums_idr, chip, chip->dev_num);
mutex_unlock(&idr_lock);

return rc;
+ err_4:
+ cdev_del(&chip->cdevs);
+ err_3:
+ device_del(&chip->dev);
+ err_2:
+ cdev_del(&chip->cdev);
+ err_1:
+ return rc;
}

static void tpm_del_char_device(struct tpm_chip *chip)
@@ -271,6 +328,11 @@ static void tpm_del_char_device(struct tpm_chip *chip)
cdev_del(&chip->cdev);
device_del(&chip->dev);

+ if (chip->flags & TPM_CHIP_FLAG_TPM2) {
+ cdev_del(&chip->cdevs);
+ device_del(&chip->devs);
+ }
+
/* Make the chip unavailable. */
mutex_lock(&idr_lock);
idr_replace(&dev_nums_idr, NULL, chip->dev_num);
@@ -282,6 +344,9 @@ static void tpm_del_char_device(struct tpm_chip *chip)
tpm2_shutdown(chip, TPM2_SU_CLEAR);
chip->ops = NULL;
up_write(&chip->ops_sem);
+ /* will release the devs reference to the chip->dev unless
+ * something has cdevs open */
+ put_device(&chip->devs);
}

static void tpm_del_legacy_sysfs(struct tpm_chip *chip)
diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index ef72c28..70ee347 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -1241,9 +1241,17 @@ static int __init tpm_init(void)
return PTR_ERR(tpm_class);
}

- rc = alloc_chrdev_region(&tpm_devt, 0, TPM_NUM_DEVICES, "tpm");
+ tpms_class = class_create(THIS_MODULE, "tpms");
+ if (IS_ERR(tpms_class)) {
+ pr_err("couldn't create tpms class\n");
+ class_destroy(tpm_class);
+ return PTR_ERR(tpms_class);
+ }
+
+ rc = alloc_chrdev_region(&tpm_devt, 0, 2*TPM_NUM_DEVICES, "tpm");
if (rc < 0) {
pr_err("tpm: failed to allocate char dev region\n");
+ class_destroy(tpms_class);
class_destroy(tpm_class);
return rc;
}
@@ -1255,7 +1263,8 @@ static void __exit tpm_exit(void)
{
idr_destroy(&dev_nums_idr);
class_destroy(tpm_class);
- unregister_chrdev_region(tpm_devt, TPM_NUM_DEVICES);
+ class_destroy(tpms_class);
+ unregister_chrdev_region(tpm_devt, 2*TPM_NUM_DEVICES);
}

subsys_initcall(tpm_init);
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 37c9760..fdc916c 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -174,7 +174,9 @@ struct tpm_chip_seqops {

struct tpm_chip {
struct device dev;
+ struct device devs;
struct cdev cdev;
+ struct cdev cdevs;

/* A driver callback under ops cannot be run unless ops_sem is held
* (sometimes implicitly, eg for the sysfs code). ops becomes null
@@ -511,8 +513,10 @@ static inline void tpm_buf_append_u32(struct tpm_buf *buf, const u32 value)
}

extern struct class *tpm_class;
+extern struct class *tpms_class;
extern dev_t tpm_devt;
extern const struct file_operations tpm_fops;
+extern const struct file_operations tpms_fops;
extern struct idr dev_nums_idr;

enum tpm_transmit_flags {
diff --git a/drivers/char/tpm/tpms-dev.c b/drivers/char/tpm/tpms-dev.c
new file mode 100644
index 0000000..2ac2537
--- /dev/null
+++ b/drivers/char/tpm/tpms-dev.c
@@ -0,0 +1,65 @@
+/*
+ * Copyright (C) 2017 James.Bottomley@HansenPartnership.com
+ *
+ * GPLv2
+ */
+#include <linux/slab.h>
+#include "tpm-dev.h"
+
+struct tpms_priv {
+ struct file_priv priv;
+ struct tpm_space space;
+};
+
+static int tpms_open(struct inode *inode, struct file *file)
+{
+ struct tpm_chip *chip;
+ struct tpms_priv *priv;
+ int rc;
+
+ chip = container_of(inode->i_cdev, struct tpm_chip, cdevs);
+ priv = kzalloc(sizeof(*priv), GFP_KERNEL);
+ if (priv == NULL)
+ return -ENOMEM;
+
+ rc = tpm2_init_space(chip, &priv->space);
+ if (rc) {
+ kfree(priv);
+ return -ENOMEM;
+ }
+
+ tpm_common_open(file, chip, &priv->priv);
+
+ return 0;
+}
+
+static int tpms_release(struct inode *inode, struct file *file)
+{
+ struct file_priv *fpriv = file->private_data;
+ struct tpms_priv *priv = container_of(fpriv, struct tpms_priv, priv);
+
+ tpm_common_release(file, fpriv);
+ kfree(priv->space.context_buf);
+ kfree(priv);
+
+ return 0;
+}
+
+ssize_t tpms_write(struct file *file, const char __user *buf,
+ size_t size, loff_t *off)
+{
+ struct file_priv *fpriv = file->private_data;
+ struct tpms_priv *priv = container_of(fpriv, struct tpms_priv, priv);
+
+ return tpm_common_write(file, buf, size, off, &priv->space);
+}
+
+const struct file_operations tpms_fops = {
+ .owner = THIS_MODULE,
+ .llseek = no_llseek,
+ .open = tpms_open,
+ .read = tpm_common_read,
+ .write = tpms_write,
+ .release = tpms_release,
+};
+
--
2.9.3