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Date: Tue, 3 Jan 2017 15:07:20 -0800
From: Kees Cook <keescook@...omium.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Matthew Garrett <mjg59@...eos.com>,
kernel-hardening@...ts.openwall.com
Subject: [PATCH] Allow userspace to request device probing even if
defer_all_probes is true
From: Matthew Garrett <mjg59@...eos.com>
Userspace may wish to make a policy decision to allow certain devices
to be attached, such as keyboards. Add a force_probe sysfs node to each
device, which if written will trigger a probe even if defer_all_probes is
currently true.
Signed-off-by: Matthew Garrett <mjg59@...eos.com>
Signed-off-by: Kees Cook <keescook@...omium.org>
---
.../ABI/testing/sysfs-devices-force_probe | 10 +++++
drivers/base/base.h | 4 +-
drivers/base/bus.c | 2 +-
drivers/base/core.c | 7 ++-
drivers/base/dd.c | 51 ++++++++++++++++++----
5 files changed, 62 insertions(+), 12 deletions(-)
create mode 100644 Documentation/ABI/testing/sysfs-devices-force_probe
diff --git a/Documentation/ABI/testing/sysfs-devices-force_probe b/Documentation/ABI/testing/sysfs-devices-force_probe
new file mode 100644
index 000000000000..3a69b9e3b86b
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-devices-force_probe
@@ -0,0 +1,10 @@
+What: /sys/devices/.../force_probe
+Date: December 2016
+KernelVersion: 4.11
+Contact: Matthew Garrett <mjg59@...f.ucam.org>
+Description:
+ The /sys/devices/.../force_probe attribute is
+ present for all devices. If deferred probing is globally
+ enabled and the device has no driver bound, a write to this
+ node will trigger probing. This attribute reads as 1 if the
+ device currently has a driver bound, and 0 otherwise.
diff --git a/drivers/base/base.h b/drivers/base/base.h
index 7bee2e4e38ce..787ab5b9a16f 100644
--- a/drivers/base/base.h
+++ b/drivers/base/base.h
@@ -112,7 +112,8 @@ extern void device_release_driver_internal(struct device *dev,
struct device *parent);
extern void driver_detach(struct device_driver *drv);
-extern int driver_probe_device(struct device_driver *drv, struct device *dev);
+extern int driver_probe_device(struct device_driver *drv, struct device *dev,
+ bool force);
extern void driver_deferred_probe_del(struct device *dev);
static inline int driver_match_device(struct device_driver *drv,
struct device *dev)
@@ -140,6 +141,7 @@ extern struct kset *devices_kset;
extern void devices_kset_move_last(struct device *dev);
extern struct device_attribute dev_attr_deferred_probe;
+extern struct device_attribute dev_attr_force_probe;
#if defined(CONFIG_MODULES) && defined(CONFIG_SYSFS)
extern void module_add_driver(struct module *mod, struct device_driver *drv);
diff --git a/drivers/base/bus.c b/drivers/base/bus.c
index 6470eb8088f4..0d4a771abdd9 100644
--- a/drivers/base/bus.c
+++ b/drivers/base/bus.c
@@ -216,7 +216,7 @@ static ssize_t bind_store(struct device_driver *drv, const char *buf,
if (dev->parent) /* Needed for USB */
device_lock(dev->parent);
device_lock(dev);
- err = driver_probe_device(drv, dev);
+ err = driver_probe_device(drv, dev, true);
device_unlock(dev);
if (dev->parent)
device_unlock(dev->parent);
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 020ea7f05520..0c6469c57de6 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -1064,8 +1064,13 @@ static int device_add_attrs(struct device *dev)
if (error)
goto err_remove_online;
- return 0;
+ error = device_create_file(dev, &dev_attr_force_probe);
+ if (error)
+ goto err_remove_deferred_probe;
+ return 0;
+ err_remove_deferred_probe:
+ device_remove_file(dev, &dev_attr_deferred_probe);
err_remove_online:
device_remove_file(dev, &dev_attr_online);
err_remove_dev_groups:
diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 4d70fa41132c..8270348b9dc7 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -344,14 +344,15 @@ EXPORT_SYMBOL_GPL(device_bind_driver);
static atomic_t probe_count = ATOMIC_INIT(0);
static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
-static int really_probe(struct device *dev, struct device_driver *drv)
+static int really_probe(struct device *dev, struct device_driver *drv,
+ bool force)
{
int ret = -EPROBE_DEFER;
int local_trigger_count = atomic_read(&deferred_trigger_count);
bool test_remove = IS_ENABLED(CONFIG_DEBUG_TEST_DRIVER_REMOVE) &&
!drv->suppress_bind_attrs;
- if (defer_all_probes) {
+ if (defer_all_probes && !force) {
/*
* Value of defer_all_probes can be set only by
* device_defer_all_probes_enable() which, in turn, will call
@@ -527,7 +528,8 @@ EXPORT_SYMBOL_GPL(wait_for_device_probe);
*
* If the device has a parent, runtime-resume the parent before driver probing.
*/
-int driver_probe_device(struct device_driver *drv, struct device *dev)
+int driver_probe_device(struct device_driver *drv, struct device *dev,
+ bool force)
{
int ret = 0;
@@ -542,7 +544,7 @@ int driver_probe_device(struct device_driver *drv, struct device *dev)
pm_runtime_get_sync(dev->parent);
pm_runtime_barrier(dev);
- ret = really_probe(dev, drv);
+ ret = really_probe(dev, drv, force);
pm_request_idle(dev);
if (dev->parent)
@@ -600,6 +602,12 @@ struct device_attach_data {
* driver, we'll encounter one that requests asynchronous probing.
*/
bool have_async;
+
+ /*
+ * Indicate whether probing should be forced even if defer_all_probes
+ * is set
+ */
+ bool force;
};
static int __device_attach_driver(struct device_driver *drv, void *_data)
@@ -638,7 +646,7 @@ static int __device_attach_driver(struct device_driver *drv, void *_data)
if (data->check_async && async_allowed != data->want_async)
return 0;
- return driver_probe_device(drv, dev);
+ return driver_probe_device(drv, dev, data->force);
}
static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
@@ -648,6 +656,7 @@ static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
.dev = dev,
.check_async = true,
.want_async = true,
+ .force = false,
};
device_lock(dev);
@@ -668,7 +677,7 @@ static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
put_device(dev);
}
-static int __device_attach(struct device *dev, bool allow_async)
+static int __device_attach(struct device *dev, bool allow_async, bool force)
{
int ret = 0;
@@ -690,6 +699,7 @@ static int __device_attach(struct device *dev, bool allow_async)
.dev = dev,
.check_async = allow_async,
.want_async = false,
+ .force = force,
};
if (dev->parent)
@@ -736,13 +746,36 @@ static int __device_attach(struct device *dev, bool allow_async)
*/
int device_attach(struct device *dev)
{
- return __device_attach(dev, false);
+ return __device_attach(dev, false, false);
}
EXPORT_SYMBOL_GPL(device_attach);
+/*
+ * Allow userspace to trigger the probing of a device even if driver probing
+ * is currently forcibly deferred
+ */
+static ssize_t force_probe_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ int ret;
+
+ ret = __device_attach(dev, false, true);
+ if (ret < 0)
+ return ret;
+ return count;
+}
+
+static ssize_t force_probe_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%d\n", device_is_bound(dev));
+}
+DEVICE_ATTR_RW(force_probe);
+
void device_initial_probe(struct device *dev)
{
- __device_attach(dev, true);
+ __device_attach(dev, true, false);
}
static int __driver_attach(struct device *dev, void *data)
@@ -776,7 +809,7 @@ static int __driver_attach(struct device *dev, void *data)
device_lock(dev->parent);
device_lock(dev);
if (!dev->driver)
- driver_probe_device(drv, dev);
+ driver_probe_device(drv, dev, false);
device_unlock(dev);
if (dev->parent)
device_unlock(dev->parent);
--
2.7.4
--
Kees Cook
Nexus Security
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