Re: [PATCH 1/3] integrity: TPM internel kernel interface

Serge E. Hallyn
2008-10-14T22:23:29Z

Quoting Mimi Zohar (zohar@linux.vnet.ibm.com):
> The internal TPM kernel interface did not protect itself from
> the removal of the TPM driver, while being used. We continue
> to protect the tpm_chip_list using the driver_lock as before,
> and are using an rcu lock to protect readers. The internal TPM

I still would like to see this spelled out somewhere - correct me
if I'm wrong but none of the patches sent so far have this spelled
out in in-line comments, do they?

It does look sane:

1. writes to tpm_chip_list are protected by driver_lock
2. readers of the list are protected by rcu
3. chips which are read from the tpm_chip_list, if they
are used outside of the rcu_read_lock(), are pinned
using get_device(chip->dev) before releasing the
rcu_read_lock.

Like I say it looks sane, but something like the above summary
could stand to be in a comment on top of tpm.c or something.

> kernel interface now protects itself from the driver being
> removed by incrementing the module reference count.
>
> Resubmitting integrity-tpm-internal-kernel-interface.patch, which
> was previously Signed-off-by Kylene Hall.
> Updated per feedback:
>
> Adds the following support:
> - make internal kernel interface to transmit TPM commands global
> - adds reading a pcr value
> - adds extending a pcr value
> - adds lookup the tpm_chip for given chip number and type
>
> Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
> Signed-off-by: Rajiv Andrade <srajiv@linux.vnet.ibm.com>

Now there are other, existing callers of tpm_transmit. Are they
all protected by sysfs pinning the kobject and thereby the device,
for the duration of the call?

thanks,
-serge

> ---
> diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c
> index 1fee703..bcef771 100644
> --- a/drivers/char/tpm/tpm.c
> +++ b/drivers/char/tpm/tpm.c
> @@ -1,11 +1,12 @@
> /*
> - * Copyright (C) 2004 IBM Corporation
> + * Copyright (C) 2004,2007,2008 IBM Corporation
> *
> * Authors:
> * Leendert van Doorn <leendert@watson.ibm.com>
> * Dave Safford <safford@watson.ibm.com>
> * Reiner Sailer <sailer@watson.ibm.com>
> * Kylene Hall <kjhall@us.ibm.com>
> + * Debora Velarde <dvelarde@us.ibm.com>
> *
> * Maintained by: <tpmdd-devel@lists.sourceforge.net>
> *
> @@ -28,6 +29,14 @@
> #include <linux/spinlock.h>
> #include <linux/smp_lock.h>
>
> +#include <linux/mm.h>
> +#include <linux/slab.h>
> +#include <linux/string.h>
> +#include <linux/crypto.h>
> +#include <linux/fs.h>
> +#include <linux/scatterlist.h>
> +#include <linux/rcupdate.h>
> +#include <asm/unaligned.h>
> #include "tpm.h"
>
> enum tpm_const {
> @@ -50,6 +59,8 @@ enum tpm_duration {
> static LIST_HEAD(tpm_chip_list);
> static DEFINE_SPINLOCK(driver_lock);
> static DECLARE_BITMAP(dev_mask, TPM_NUM_DEVICES);
> +#define TPM_CHIP_NUM_MASK 0x0000ffff
> +#define TPM_CHIP_TYPE_SHIFT 16
>
> /*
> * Array with one entry per ordinal defining the maximum amount
> @@ -366,8 +377,7 @@ EXPORT_SYMBOL_GPL(tpm_calc_ordinal_duration);
> /*
> * Internal kernel interface to transmit TPM commands
> */
> -static ssize_t tpm_transmit(struct tpm_chip *chip, const char *buf,
> - size_t bufsiz)
> +ssize_t tpm_transmit(struct tpm_chip *chip, char *buf, size_t bufsiz)
> {
> ssize_t rc;
> u32 count, ordinal;
> @@ -425,6 +435,7 @@ out:
> mutex_unlock(&chip->tpm_mutex);
> return rc;
> }
> +EXPORT_SYMBOL_GPL(tpm_transmit);
>
> #define TPM_DIGEST_SIZE 20
> #define TPM_ERROR_SIZE 10
> @@ -710,6 +721,7 @@ ssize_t tpm_show_temp_deactivated(struct device * dev,
> }
> EXPORT_SYMBOL_GPL(tpm_show_temp_deactivated);
>
> +#define READ_PCR_RESULT_SIZE 30
> static const u8 pcrread[] = {
> 0, 193, /* TPM_TAG_RQU_COMMAND */
> 0, 0, 0, 14, /* length */
> @@ -765,6 +777,128 @@ out:
> }
> EXPORT_SYMBOL_GPL(tpm_show_pcrs);
>
> +/*
> + * tpm_chip_lookup - return tpm_chip for given chip number and type
> + *
> + * Must be called with rcu_read_lock.
> + */
> +static struct tpm_chip *tpm_chip_lookup(int chip_num, int chip_typ)
> +{
> + struct tpm_chip *pos;
> + int rc;
> +
> + list_for_each_entry_rcu(pos, &tpm_chip_list, list) {
> + rc = (chip_num == TPM_ANY_NUM || pos->dev_num == chip_num)
> + && (chip_typ == TPM_ANY_TYPE);
> + if (rc)
> + return pos;
> + }
> + return NULL;
> +}
> +
> +/**
> + * tpm_pcr_read - read a pcr value
> + * @chip_id: tpm chip identifier
> + * Upper 2 bytes: ANY, HW_ONLY or SW_ONLY
> + * Lower 2 bytes: tpm idx # or AN&
> + * @pcr_idx: pcr idx to retrieve
> + * @res_buf: TPM_PCR value
> + * size of res_buf is 20 bytes (or NULL if you don't care)
> + *
> + * The TPM driver should be built-in, but for whatever reason it
> + * isn't, protect against the chip disappearing, by incrementing
> + * the module usage count.
> + */
> +int tpm_pcr_read(u32 chip_id, int pcr_idx, u8 *res_buf)
> +{
> + u8 data[READ_PCR_RESULT_SIZE];
> + int rc;
> + __be32 index;
> + int chip_num = chip_id & TPM_CHIP_NUM_MASK;
> + struct tpm_chip *chip;
> +
> + rcu_read_lock();
> + chip = tpm_chip_lookup(chip_num, chip_id >> TPM_CHIP_TYPE_SHIFT);
> + if (chip == NULL) {
> + rcu_read_unlock();
> + return -ENODEV;
> + }
> + if (!try_module_get(chip->dev->driver->owner)) {
> + rcu_read_unlock();
> + return -ENODEV;
> + }
> + rcu_read_unlock();
> +
> + BUILD_BUG_ON(sizeof(pcrread) > READ_PCR_RESULT_SIZE);
> + memcpy(data, pcrread, sizeof(pcrread));
> + index = cpu_to_be32(pcr_idx);
> + memcpy(data + 10, &index, 4);
> + rc = tpm_transmit(chip, data, sizeof(data));
> + if (rc > 0)
> + rc = get_unaligned_be32((__be32 *) (data + 6));
> +
> + if (rc == 0 && res_buf)
> + memcpy(res_buf, data + 10, TPM_DIGEST_SIZE);
> +
> + module_put(chip->dev->driver->owner);
> + return rc;
> +}
> +EXPORT_SYMBOL_GPL(tpm_pcr_read);
> +
> +#define EXTEND_PCR_SIZE 34
> +static const u8 pcrextend[] = {
> + 0, 193, /* TPM_TAG_RQU_COMMAND */
> + 0, 0, 0, 34, /* length */
> + 0, 0, 0, 20, /* TPM_ORD_Extend */
> + 0, 0, 0, 0 /* PCR index */
> +};
> +
> +/**
> + * tpm_pcr_extend - extend pcr value with hash
> + * @chip_id: tpm chip identifier
> + * Upper 2 bytes: ANY, HW_ONLY or SW_ONLY
> + * Lower 2 bytes: tpm idx # or AN&
> + * @pcr_idx: pcr idx to extend
> + * @hash: hash value used to extend pcr value
> + *
> + * The TPM driver should be built-in, but for whatever reason it
> + * isn't, protect against the chip disappearing, by incrementing
> + * the module usage count.
> + */
> +int tpm_pcr_extend(u32 chip_id, int pcr_idx, const u8 *hash)
> +{
> + u8 data[EXTEND_PCR_SIZE];
> + int rc;
> + __be32 index;
> + int chip_num = chip_id & TPM_CHIP_NUM_MASK;
> + struct tpm_chip *chip;
> +
> + rcu_read_lock();
> + chip = tpm_chip_lookup(chip_num, chip_id >> TPM_CHIP_TYPE_SHIFT);
> + if (chip == NULL) {
> + rcu_read_unlock();
> + return -ENODEV;
> + }
> + if (!try_module_get(chip->dev->driver->owner)) {
> + rcu_read_unlock();
> + return -ENODEV;
> + }
> + rcu_read_unlock();
> +
> + BUILD_BUG_ON(sizeof(pcrextend) > EXTEND_PCR_SIZE);
> + memcpy(data, pcrextend, sizeof(pcrextend));
> + index = cpu_to_be32(pcr_idx);
> + memcpy(data + 10, &index, 4);
> + memcpy(data + 14, hash, TPM_DIGEST_SIZE);
> + rc = tpm_transmit(chip, data, sizeof(data));
> + if (rc > 0)
> + rc = get_unaligned_be32((__be32 *) (data + 6));
> +
> + module_put(chip->dev->driver->owner);
> + return rc;
> +}
> +EXPORT_SYMBOL_GPL(tpm_pcr_extend);
> +
> #define READ_PUBEK_RESULT_SIZE 314
> static const u8 readpubek[] = {
> 0, 193, /* TPM_TAG_RQU_COMMAND */
> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> index 8e30df4..e0ffddb 100644
> --- a/drivers/char/tpm/tpm.h
> +++ b/drivers/char/tpm/tpm.h
> @@ -1,5 +1,5 @@
> /*
> - * Copyright (C) 2004 IBM Corporation
> + * Copyright (C) 2004, 2007, 2008 IBM Corporation
> *
> * Authors:
> * Leendert van Doorn <leendert@watson.ibm.com>
> @@ -26,6 +26,7 @@
> #include <linux/miscdevice.h>
> #include <linux/platform_device.h>
> #include <linux/io.h>
> +#include <linux/tpm.h>
>
> enum tpm_timeout {
> TPM_TIMEOUT = 5, /* msecs */
> @@ -128,6 +129,7 @@ extern void tpm_get_timeouts(struct tpm_chip *);
> extern void tpm_gen_interrupt(struct tpm_chip *);
> extern void tpm_continue_selftest(struct tpm_chip *);
> extern unsigned long tpm_calc_ordinal_duration(struct tpm_chip *, u32);
> +ssize_t tpm_transmit(struct tpm_chip *chip, char *buf, size_t bufsiz);
> extern struct tpm_chip* tpm_register_hardware(struct device *,
> const struct tpm_vendor_specific *);
> extern int tpm_open(struct inode *, struct file *);
> diff --git a/drivers/char/tpm/tpm_tis.c b/drivers/char/tpm/tpm_tis.c
> index 717af7a..bc26116 100644
> --- a/drivers/char/tpm/tpm_tis.c
> +++ b/drivers/char/tpm/tpm_tis.c
> @@ -642,6 +642,9 @@ static __devexit void tpm_tis_pnp_remove(struct pnp_dev *dev)
>
> static struct pnp_driver tis_pnp_driver = {
> .name = "tpm_tis",
> + .driver = {
> + .owner = THIS_MODULE,
> + },
> .id_table = tpm_pnp_tbl,
> .probe = tpm_tis_pnp_init,
> .suspend = tpm_tis_pnp_suspend,
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> new file mode 100644
> index 0000000..355a442
> --- /dev/null
> +++ b/include/linux/tpm.h
> @@ -0,0 +1,49 @@
> +/*
> + * Copyright (C) 2004,2007,2008 IBM Corporation
> + *
> + * Authors:
> + * Leendert van Doorn <leendert@watson.ibm.com>
> + * Dave Safford <safford@watson.ibm.com>
> + * Reiner Sailer <sailer@watson.ibm.com>
> + * Kylene Hall <kjhall@us.ibm.com>
> + * Debora Velarde <dvelarde@us.ibm.com>
> + *
> + * Maintained by: <tpmdd_devel@lists.sourceforge.net>
> + *
> + * Device driver for TCG/TCPA TPM (trusted platform module).
> + * Specifications at www.trustedcomputinggroup.org
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License as
> + * published by the Free Software Foundation, version 2 of the
> + * License.
> + *
> + */
> +#ifndef __LINUX_TPM_H__
> +#define __LINUX_TPM_H__
> +
> +#define PCI_DEVICE_ID_AMD_8111_LPC 0x7468
> +
> +/*
> + * Chip type is one of these values in the upper two bytes of chip_id
> + */
> +enum tpm_chip_type {
> + TPM_HW_TYPE = 0x0,
> + TPM_SW_TYPE = 0x1,
> + TPM_ANY_TYPE = 0xFFFF,
> +};
> +
> +/*
> + * Chip num is this value or a valid tpm idx in lower two bytes of chip_id
> + */
> +enum tpm_chip_num {
> + TPM_ANY_NUM = 0xFFFF,
> +};
> +
> +
> +#if defined(CONFIG_TCG_TPM) || defined(CONFIG_TCG_TPM_MODULE)
> +
> +extern int tpm_pcr_read(u32 chip_id, int pcr_idx, u8 *res_buf);
> +extern int tpm_pcr_extend(u32 chip_id, int pcr_idx, const u8 *hash);
> +#endif
> +#endif
> --
> 1.5.5.1
>
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