linux/drivers/thunderbolt/domain.c
Mika Westerberg dcc3c9e37f thunderbolt: Export IOMMU based DMA protection support to userspace
Recent systems with Thunderbolt ports may support IOMMU natively. In
practice this means that Thunderbolt connected devices are placed behind
an IOMMU during the whole time it is connected (including during boot)
making Thunderbolt security levels redundant. This is called Kernel DMA
protection [1] by Microsoft.

Some of these systems still have Thunderbolt security level set to
"user" in order to support OS downgrade (the older version of the OS
might not support IOMMU based DMA protection so connecting a device
still relies on user approval).

Export this information to userspace by introducing a new sysfs
attribute (iommu_dma_protection). Based on it userspace tools can make
more accurate decision whether or not authorize the connected device.

In addition update Thunderbolt documentation regarding IOMMU based DMA
protection.

[1] https://docs.microsoft.com/en-us/windows/security/information-protection/kernel-dma-protection-for-thunderbolt

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Yehezkel Bernat <YehezkelShB@gmail.com>
2018-12-05 12:01:56 +03:00

819 lines
19 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Thunderbolt bus support
*
* Copyright (C) 2017, Intel Corporation
* Author: Mika Westerberg <mika.westerberg@linux.intel.com>
*/
#include <linux/device.h>
#include <linux/dmar.h>
#include <linux/idr.h>
#include <linux/iommu.h>
#include <linux/module.h>
#include <linux/pm_runtime.h>
#include <linux/slab.h>
#include <linux/random.h>
#include <crypto/hash.h>
#include "tb.h"
static DEFINE_IDA(tb_domain_ida);
static bool match_service_id(const struct tb_service_id *id,
const struct tb_service *svc)
{
if (id->match_flags & TBSVC_MATCH_PROTOCOL_KEY) {
if (strcmp(id->protocol_key, svc->key))
return false;
}
if (id->match_flags & TBSVC_MATCH_PROTOCOL_ID) {
if (id->protocol_id != svc->prtcid)
return false;
}
if (id->match_flags & TBSVC_MATCH_PROTOCOL_VERSION) {
if (id->protocol_version != svc->prtcvers)
return false;
}
if (id->match_flags & TBSVC_MATCH_PROTOCOL_VERSION) {
if (id->protocol_revision != svc->prtcrevs)
return false;
}
return true;
}
static const struct tb_service_id *__tb_service_match(struct device *dev,
struct device_driver *drv)
{
struct tb_service_driver *driver;
const struct tb_service_id *ids;
struct tb_service *svc;
svc = tb_to_service(dev);
if (!svc)
return NULL;
driver = container_of(drv, struct tb_service_driver, driver);
if (!driver->id_table)
return NULL;
for (ids = driver->id_table; ids->match_flags != 0; ids++) {
if (match_service_id(ids, svc))
return ids;
}
return NULL;
}
static int tb_service_match(struct device *dev, struct device_driver *drv)
{
return !!__tb_service_match(dev, drv);
}
static int tb_service_probe(struct device *dev)
{
struct tb_service *svc = tb_to_service(dev);
struct tb_service_driver *driver;
const struct tb_service_id *id;
driver = container_of(dev->driver, struct tb_service_driver, driver);
id = __tb_service_match(dev, &driver->driver);
return driver->probe(svc, id);
}
static int tb_service_remove(struct device *dev)
{
struct tb_service *svc = tb_to_service(dev);
struct tb_service_driver *driver;
driver = container_of(dev->driver, struct tb_service_driver, driver);
if (driver->remove)
driver->remove(svc);
return 0;
}
static void tb_service_shutdown(struct device *dev)
{
struct tb_service_driver *driver;
struct tb_service *svc;
svc = tb_to_service(dev);
if (!svc || !dev->driver)
return;
driver = container_of(dev->driver, struct tb_service_driver, driver);
if (driver->shutdown)
driver->shutdown(svc);
}
static const char * const tb_security_names[] = {
[TB_SECURITY_NONE] = "none",
[TB_SECURITY_USER] = "user",
[TB_SECURITY_SECURE] = "secure",
[TB_SECURITY_DPONLY] = "dponly",
[TB_SECURITY_USBONLY] = "usbonly",
};
static ssize_t boot_acl_show(struct device *dev, struct device_attribute *attr,
char *buf)
{
struct tb *tb = container_of(dev, struct tb, dev);
uuid_t *uuids;
ssize_t ret;
int i;
uuids = kcalloc(tb->nboot_acl, sizeof(uuid_t), GFP_KERNEL);
if (!uuids)
return -ENOMEM;
pm_runtime_get_sync(&tb->dev);
if (mutex_lock_interruptible(&tb->lock)) {
ret = -ERESTARTSYS;
goto out;
}
ret = tb->cm_ops->get_boot_acl(tb, uuids, tb->nboot_acl);
if (ret) {
mutex_unlock(&tb->lock);
goto out;
}
mutex_unlock(&tb->lock);
for (ret = 0, i = 0; i < tb->nboot_acl; i++) {
if (!uuid_is_null(&uuids[i]))
ret += snprintf(buf + ret, PAGE_SIZE - ret, "%pUb",
&uuids[i]);
ret += snprintf(buf + ret, PAGE_SIZE - ret, "%s",
i < tb->nboot_acl - 1 ? "," : "\n");
}
out:
pm_runtime_mark_last_busy(&tb->dev);
pm_runtime_put_autosuspend(&tb->dev);
kfree(uuids);
return ret;
}
static ssize_t boot_acl_store(struct device *dev, struct device_attribute *attr,
const char *buf, size_t count)
{
struct tb *tb = container_of(dev, struct tb, dev);
char *str, *s, *uuid_str;
ssize_t ret = 0;
uuid_t *acl;
int i = 0;
/*
* Make sure the value is not bigger than tb->nboot_acl * UUID
* length + commas and optional "\n". Also the smallest allowable
* string is tb->nboot_acl * ",".
*/
if (count > (UUID_STRING_LEN + 1) * tb->nboot_acl + 1)
return -EINVAL;
if (count < tb->nboot_acl - 1)
return -EINVAL;
str = kstrdup(buf, GFP_KERNEL);
if (!str)
return -ENOMEM;
acl = kcalloc(tb->nboot_acl, sizeof(uuid_t), GFP_KERNEL);
if (!acl) {
ret = -ENOMEM;
goto err_free_str;
}
uuid_str = strim(str);
while ((s = strsep(&uuid_str, ",")) != NULL && i < tb->nboot_acl) {
size_t len = strlen(s);
if (len) {
if (len != UUID_STRING_LEN) {
ret = -EINVAL;
goto err_free_acl;
}
ret = uuid_parse(s, &acl[i]);
if (ret)
goto err_free_acl;
}
i++;
}
if (s || i < tb->nboot_acl) {
ret = -EINVAL;
goto err_free_acl;
}
pm_runtime_get_sync(&tb->dev);
if (mutex_lock_interruptible(&tb->lock)) {
ret = -ERESTARTSYS;
goto err_rpm_put;
}
ret = tb->cm_ops->set_boot_acl(tb, acl, tb->nboot_acl);
if (!ret) {
/* Notify userspace about the change */
kobject_uevent(&tb->dev.kobj, KOBJ_CHANGE);
}
mutex_unlock(&tb->lock);
err_rpm_put:
pm_runtime_mark_last_busy(&tb->dev);
pm_runtime_put_autosuspend(&tb->dev);
err_free_acl:
kfree(acl);
err_free_str:
kfree(str);
return ret ?: count;
}
static DEVICE_ATTR_RW(boot_acl);
static ssize_t iommu_dma_protection_show(struct device *dev,
struct device_attribute *attr,
char *buf)
{
/*
* Kernel DMA protection is a feature where Thunderbolt security is
* handled natively using IOMMU. It is enabled when IOMMU is
* enabled and ACPI DMAR table has DMAR_PLATFORM_OPT_IN set.
*/
return sprintf(buf, "%d\n",
iommu_present(&pci_bus_type) && dmar_platform_optin());
}
static DEVICE_ATTR_RO(iommu_dma_protection);
static ssize_t security_show(struct device *dev, struct device_attribute *attr,
char *buf)
{
struct tb *tb = container_of(dev, struct tb, dev);
const char *name = "unknown";
if (tb->security_level < ARRAY_SIZE(tb_security_names))
name = tb_security_names[tb->security_level];
return sprintf(buf, "%s\n", name);
}
static DEVICE_ATTR_RO(security);
static struct attribute *domain_attrs[] = {
&dev_attr_boot_acl.attr,
&dev_attr_iommu_dma_protection.attr,
&dev_attr_security.attr,
NULL,
};
static umode_t domain_attr_is_visible(struct kobject *kobj,
struct attribute *attr, int n)
{
struct device *dev = container_of(kobj, struct device, kobj);
struct tb *tb = container_of(dev, struct tb, dev);
if (attr == &dev_attr_boot_acl.attr) {
if (tb->nboot_acl &&
tb->cm_ops->get_boot_acl &&
tb->cm_ops->set_boot_acl)
return attr->mode;
return 0;
}
return attr->mode;
}
static struct attribute_group domain_attr_group = {
.is_visible = domain_attr_is_visible,
.attrs = domain_attrs,
};
static const struct attribute_group *domain_attr_groups[] = {
&domain_attr_group,
NULL,
};
struct bus_type tb_bus_type = {
.name = "thunderbolt",
.match = tb_service_match,
.probe = tb_service_probe,
.remove = tb_service_remove,
.shutdown = tb_service_shutdown,
};
static void tb_domain_release(struct device *dev)
{
struct tb *tb = container_of(dev, struct tb, dev);
tb_ctl_free(tb->ctl);
destroy_workqueue(tb->wq);
ida_simple_remove(&tb_domain_ida, tb->index);
mutex_destroy(&tb->lock);
kfree(tb);
}
struct device_type tb_domain_type = {
.name = "thunderbolt_domain",
.release = tb_domain_release,
};
/**
* tb_domain_alloc() - Allocate a domain
* @nhi: Pointer to the host controller
* @privsize: Size of the connection manager private data
*
* Allocates and initializes a new Thunderbolt domain. Connection
* managers are expected to call this and then fill in @cm_ops
* accordingly.
*
* Call tb_domain_put() to release the domain before it has been added
* to the system.
*
* Return: allocated domain structure on %NULL in case of error
*/
struct tb *tb_domain_alloc(struct tb_nhi *nhi, size_t privsize)
{
struct tb *tb;
/*
* Make sure the structure sizes map with that the hardware
* expects because bit-fields are being used.
*/
BUILD_BUG_ON(sizeof(struct tb_regs_switch_header) != 5 * 4);
BUILD_BUG_ON(sizeof(struct tb_regs_port_header) != 8 * 4);
BUILD_BUG_ON(sizeof(struct tb_regs_hop) != 2 * 4);
tb = kzalloc(sizeof(*tb) + privsize, GFP_KERNEL);
if (!tb)
return NULL;
tb->nhi = nhi;
mutex_init(&tb->lock);
tb->index = ida_simple_get(&tb_domain_ida, 0, 0, GFP_KERNEL);
if (tb->index < 0)
goto err_free;
tb->wq = alloc_ordered_workqueue("thunderbolt%d", 0, tb->index);
if (!tb->wq)
goto err_remove_ida;
tb->dev.parent = &nhi->pdev->dev;
tb->dev.bus = &tb_bus_type;
tb->dev.type = &tb_domain_type;
tb->dev.groups = domain_attr_groups;
dev_set_name(&tb->dev, "domain%d", tb->index);
device_initialize(&tb->dev);
return tb;
err_remove_ida:
ida_simple_remove(&tb_domain_ida, tb->index);
err_free:
kfree(tb);
return NULL;
}
static bool tb_domain_event_cb(void *data, enum tb_cfg_pkg_type type,
const void *buf, size_t size)
{
struct tb *tb = data;
if (!tb->cm_ops->handle_event) {
tb_warn(tb, "domain does not have event handler\n");
return true;
}
switch (type) {
case TB_CFG_PKG_XDOMAIN_REQ:
case TB_CFG_PKG_XDOMAIN_RESP:
return tb_xdomain_handle_request(tb, type, buf, size);
default:
tb->cm_ops->handle_event(tb, type, buf, size);
}
return true;
}
/**
* tb_domain_add() - Add domain to the system
* @tb: Domain to add
*
* Starts the domain and adds it to the system. Hotplugging devices will
* work after this has been returned successfully. In order to remove
* and release the domain after this function has been called, call
* tb_domain_remove().
*
* Return: %0 in case of success and negative errno in case of error
*/
int tb_domain_add(struct tb *tb)
{
int ret;
if (WARN_ON(!tb->cm_ops))
return -EINVAL;
mutex_lock(&tb->lock);
tb->ctl = tb_ctl_alloc(tb->nhi, tb_domain_event_cb, tb);
if (!tb->ctl) {
ret = -ENOMEM;
goto err_unlock;
}
/*
* tb_schedule_hotplug_handler may be called as soon as the config
* channel is started. Thats why we have to hold the lock here.
*/
tb_ctl_start(tb->ctl);
if (tb->cm_ops->driver_ready) {
ret = tb->cm_ops->driver_ready(tb);
if (ret)
goto err_ctl_stop;
}
ret = device_add(&tb->dev);
if (ret)
goto err_ctl_stop;
/* Start the domain */
if (tb->cm_ops->start) {
ret = tb->cm_ops->start(tb);
if (ret)
goto err_domain_del;
}
/* This starts event processing */
mutex_unlock(&tb->lock);
pm_runtime_no_callbacks(&tb->dev);
pm_runtime_set_active(&tb->dev);
pm_runtime_enable(&tb->dev);
pm_runtime_set_autosuspend_delay(&tb->dev, TB_AUTOSUSPEND_DELAY);
pm_runtime_mark_last_busy(&tb->dev);
pm_runtime_use_autosuspend(&tb->dev);
return 0;
err_domain_del:
device_del(&tb->dev);
err_ctl_stop:
tb_ctl_stop(tb->ctl);
err_unlock:
mutex_unlock(&tb->lock);
return ret;
}
/**
* tb_domain_remove() - Removes and releases a domain
* @tb: Domain to remove
*
* Stops the domain, removes it from the system and releases all
* resources once the last reference has been released.
*/
void tb_domain_remove(struct tb *tb)
{
mutex_lock(&tb->lock);
if (tb->cm_ops->stop)
tb->cm_ops->stop(tb);
/* Stop the domain control traffic */
tb_ctl_stop(tb->ctl);
mutex_unlock(&tb->lock);
flush_workqueue(tb->wq);
device_unregister(&tb->dev);
}
/**
* tb_domain_suspend_noirq() - Suspend a domain
* @tb: Domain to suspend
*
* Suspends all devices in the domain and stops the control channel.
*/
int tb_domain_suspend_noirq(struct tb *tb)
{
int ret = 0;
/*
* The control channel interrupt is left enabled during suspend
* and taking the lock here prevents any events happening before
* we actually have stopped the domain and the control channel.
*/
mutex_lock(&tb->lock);
if (tb->cm_ops->suspend_noirq)
ret = tb->cm_ops->suspend_noirq(tb);
if (!ret)
tb_ctl_stop(tb->ctl);
mutex_unlock(&tb->lock);
return ret;
}
/**
* tb_domain_resume_noirq() - Resume a domain
* @tb: Domain to resume
*
* Re-starts the control channel, and resumes all devices connected to
* the domain.
*/
int tb_domain_resume_noirq(struct tb *tb)
{
int ret = 0;
mutex_lock(&tb->lock);
tb_ctl_start(tb->ctl);
if (tb->cm_ops->resume_noirq)
ret = tb->cm_ops->resume_noirq(tb);
mutex_unlock(&tb->lock);
return ret;
}
int tb_domain_suspend(struct tb *tb)
{
return tb->cm_ops->suspend ? tb->cm_ops->suspend(tb) : 0;
}
void tb_domain_complete(struct tb *tb)
{
if (tb->cm_ops->complete)
tb->cm_ops->complete(tb);
}
int tb_domain_runtime_suspend(struct tb *tb)
{
if (tb->cm_ops->runtime_suspend) {
int ret = tb->cm_ops->runtime_suspend(tb);
if (ret)
return ret;
}
tb_ctl_stop(tb->ctl);
return 0;
}
int tb_domain_runtime_resume(struct tb *tb)
{
tb_ctl_start(tb->ctl);
if (tb->cm_ops->runtime_resume) {
int ret = tb->cm_ops->runtime_resume(tb);
if (ret)
return ret;
}
return 0;
}
/**
* tb_domain_approve_switch() - Approve switch
* @tb: Domain the switch belongs to
* @sw: Switch to approve
*
* This will approve switch by connection manager specific means. In
* case of success the connection manager will create tunnels for all
* supported protocols.
*/
int tb_domain_approve_switch(struct tb *tb, struct tb_switch *sw)
{
struct tb_switch *parent_sw;
if (!tb->cm_ops->approve_switch)
return -EPERM;
/* The parent switch must be authorized before this one */
parent_sw = tb_to_switch(sw->dev.parent);
if (!parent_sw || !parent_sw->authorized)
return -EINVAL;
return tb->cm_ops->approve_switch(tb, sw);
}
/**
* tb_domain_approve_switch_key() - Approve switch and add key
* @tb: Domain the switch belongs to
* @sw: Switch to approve
*
* For switches that support secure connect, this function first adds
* key to the switch NVM using connection manager specific means. If
* adding the key is successful, the switch is approved and connected.
*
* Return: %0 on success and negative errno in case of failure.
*/
int tb_domain_approve_switch_key(struct tb *tb, struct tb_switch *sw)
{
struct tb_switch *parent_sw;
int ret;
if (!tb->cm_ops->approve_switch || !tb->cm_ops->add_switch_key)
return -EPERM;
/* The parent switch must be authorized before this one */
parent_sw = tb_to_switch(sw->dev.parent);
if (!parent_sw || !parent_sw->authorized)
return -EINVAL;
ret = tb->cm_ops->add_switch_key(tb, sw);
if (ret)
return ret;
return tb->cm_ops->approve_switch(tb, sw);
}
/**
* tb_domain_challenge_switch_key() - Challenge and approve switch
* @tb: Domain the switch belongs to
* @sw: Switch to approve
*
* For switches that support secure connect, this function generates
* random challenge and sends it to the switch. The switch responds to
* this and if the response matches our random challenge, the switch is
* approved and connected.
*
* Return: %0 on success and negative errno in case of failure.
*/
int tb_domain_challenge_switch_key(struct tb *tb, struct tb_switch *sw)
{
u8 challenge[TB_SWITCH_KEY_SIZE];
u8 response[TB_SWITCH_KEY_SIZE];
u8 hmac[TB_SWITCH_KEY_SIZE];
struct tb_switch *parent_sw;
struct crypto_shash *tfm;
struct shash_desc *shash;
int ret;
if (!tb->cm_ops->approve_switch || !tb->cm_ops->challenge_switch_key)
return -EPERM;
/* The parent switch must be authorized before this one */
parent_sw = tb_to_switch(sw->dev.parent);
if (!parent_sw || !parent_sw->authorized)
return -EINVAL;
get_random_bytes(challenge, sizeof(challenge));
ret = tb->cm_ops->challenge_switch_key(tb, sw, challenge, response);
if (ret)
return ret;
tfm = crypto_alloc_shash("hmac(sha256)", 0, 0);
if (IS_ERR(tfm))
return PTR_ERR(tfm);
ret = crypto_shash_setkey(tfm, sw->key, TB_SWITCH_KEY_SIZE);
if (ret)
goto err_free_tfm;
shash = kzalloc(sizeof(*shash) + crypto_shash_descsize(tfm),
GFP_KERNEL);
if (!shash) {
ret = -ENOMEM;
goto err_free_tfm;
}
shash->tfm = tfm;
shash->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
memset(hmac, 0, sizeof(hmac));
ret = crypto_shash_digest(shash, challenge, sizeof(hmac), hmac);
if (ret)
goto err_free_shash;
/* The returned HMAC must match the one we calculated */
if (memcmp(response, hmac, sizeof(hmac))) {
ret = -EKEYREJECTED;
goto err_free_shash;
}
crypto_free_shash(tfm);
kfree(shash);
return tb->cm_ops->approve_switch(tb, sw);
err_free_shash:
kfree(shash);
err_free_tfm:
crypto_free_shash(tfm);
return ret;
}
/**
* tb_domain_disconnect_pcie_paths() - Disconnect all PCIe paths
* @tb: Domain whose PCIe paths to disconnect
*
* This needs to be called in preparation for NVM upgrade of the host
* controller. Makes sure all PCIe paths are disconnected.
*
* Return %0 on success and negative errno in case of error.
*/
int tb_domain_disconnect_pcie_paths(struct tb *tb)
{
if (!tb->cm_ops->disconnect_pcie_paths)
return -EPERM;
return tb->cm_ops->disconnect_pcie_paths(tb);
}
/**
* tb_domain_approve_xdomain_paths() - Enable DMA paths for XDomain
* @tb: Domain enabling the DMA paths
* @xd: XDomain DMA paths are created to
*
* Calls connection manager specific method to enable DMA paths to the
* XDomain in question.
*
* Return: 0% in case of success and negative errno otherwise. In
* particular returns %-ENOTSUPP if the connection manager
* implementation does not support XDomains.
*/
int tb_domain_approve_xdomain_paths(struct tb *tb, struct tb_xdomain *xd)
{
if (!tb->cm_ops->approve_xdomain_paths)
return -ENOTSUPP;
return tb->cm_ops->approve_xdomain_paths(tb, xd);
}
/**
* tb_domain_disconnect_xdomain_paths() - Disable DMA paths for XDomain
* @tb: Domain disabling the DMA paths
* @xd: XDomain whose DMA paths are disconnected
*
* Calls connection manager specific method to disconnect DMA paths to
* the XDomain in question.
*
* Return: 0% in case of success and negative errno otherwise. In
* particular returns %-ENOTSUPP if the connection manager
* implementation does not support XDomains.
*/
int tb_domain_disconnect_xdomain_paths(struct tb *tb, struct tb_xdomain *xd)
{
if (!tb->cm_ops->disconnect_xdomain_paths)
return -ENOTSUPP;
return tb->cm_ops->disconnect_xdomain_paths(tb, xd);
}
static int disconnect_xdomain(struct device *dev, void *data)
{
struct tb_xdomain *xd;
struct tb *tb = data;
int ret = 0;
xd = tb_to_xdomain(dev);
if (xd && xd->tb == tb)
ret = tb_xdomain_disable_paths(xd);
return ret;
}
/**
* tb_domain_disconnect_all_paths() - Disconnect all paths for the domain
* @tb: Domain whose paths are disconnected
*
* This function can be used to disconnect all paths (PCIe, XDomain) for
* example in preparation for host NVM firmware upgrade. After this is
* called the paths cannot be established without resetting the switch.
*
* Return: %0 in case of success and negative errno otherwise.
*/
int tb_domain_disconnect_all_paths(struct tb *tb)
{
int ret;
ret = tb_domain_disconnect_pcie_paths(tb);
if (ret)
return ret;
return bus_for_each_dev(&tb_bus_type, NULL, tb, disconnect_xdomain);
}
int tb_domain_init(void)
{
int ret;
ret = tb_xdomain_init();
if (ret)
return ret;
ret = bus_register(&tb_bus_type);
if (ret)
tb_xdomain_exit();
return ret;
}
void tb_domain_exit(void)
{
bus_unregister(&tb_bus_type);
ida_destroy(&tb_domain_ida);
tb_switch_exit();
tb_xdomain_exit();
}