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

Rajiv Andrade
2008-10-22T12:48:04Z

On Tue, 2008-10-14 at 17:23 -0500, Serge E. Hallyn wrote:
> 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.
>
No problem, I'll submit a patch containing a proper comment section to
be applied on top of these, maybe after they get accepted.

> > 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?
>

They aren't called through sysfs, but are still protected. These new
functions get chip data consistently by using rcu_read. Then, after
computing what's intended to be written back to the chip, tpm_transmit
sends the new data while using tpm_mutex, so both operations are
performed without the risk of a race condition.

> 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
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at http://www.tux.org/lkml/
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/

--
Rajiv Andrade <srajiv@br.ibm.com>
Security Development
IBM Linux Technology Center