[Intel-gfx] [PATCH 04/10] driver core: Don't return EPROBE_DEFER to userspace during sysfs bind

Christoph Hellwig
2021-06-15T13:39:20Z

EPROBE_DEFER is an internal kernel error code and it should not be leaked
to userspace via the bind_store() sysfs. Userspace doesn't have this
constant and cannot understand it.

Further, it doesn't really make sense to have userspace trigger a deferred
probe via bind_store(), which could eventually succeed, while
simultaneously returning an error back.

Resolve this by splitting driver_probe_device so that the version used
by the sysfs binding that turns EPROBE_DEFER into -EAGAIN, while the one
used for internally binding keeps the error code, and calls
driver_deferred_probe_add where needed. This also allows to nicely split
out the defer_all_probes / probe_count checks so that they actually allow
for full device_{block,unblock}_probing protection while not bothering
the sysfs bind case.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/base/dd.c | 78 +++++++++++++++++++++++++----------------------
1 file changed, 42 insertions(+), 36 deletions(-)

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 25341f52198c..7d54bae52a8d 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -491,15 +491,6 @@ EXPORT_SYMBOL_GPL(device_bind_driver);
static atomic_t probe_count = ATOMIC_INIT(0);
static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);

-static void driver_deferred_probe_add_trigger(struct device *dev,
- int local_trigger_count)
-{
- driver_deferred_probe_add(dev);
- /* Did a trigger occur while probing? Need to re-trigger if yes */
- if (local_trigger_count != atomic_read(&deferred_trigger_count))
- driver_deferred_probe_trigger();
-}
-
static ssize_t state_synced_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
@@ -547,10 +538,9 @@ static int call_driver_probe(struct device *dev, struct device_driver *drv)

static int really_probe(struct device *dev, struct device_driver *drv)
{
- int local_trigger_count = atomic_read(&deferred_trigger_count);
bool test_remove = IS_ENABLED(CONFIG_DEBUG_TEST_DRIVER_REMOVE) &&
!drv->suppress_bind_attrs;
- int ret = -EPROBE_DEFER, probe_ret = 0;
+ int ret, probe_ret = 0;

if (defer_all_probes) {
/*
@@ -559,17 +549,13 @@ static int really_probe(struct device *dev, struct device_driver *drv)
* wait_for_device_probe() right after that to avoid any races.
*/
dev_dbg(dev, "Driver %s force probe deferral\n", drv->name);
- driver_deferred_probe_add(dev);
- return ret;
+ return -EPROBE_DEFER;
}

ret = device_links_check_suppliers(dev);
- if (ret == -EPROBE_DEFER)
- driver_deferred_probe_add_trigger(dev, local_trigger_count);
if (ret)
return ret;

- atomic_inc(&probe_count);
pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
drv->bus->name, __func__, drv->name, dev_name(dev));
if (!list_empty(&dev->devres_head)) {
@@ -681,11 +667,7 @@ static int really_probe(struct device *dev, struct device_driver *drv)
dev->pm_domain->dismiss(dev);
pm_runtime_reinit(dev);
dev_pm_set_driver_flags(dev, 0);
- if (probe_ret == -EPROBE_DEFER)
- driver_deferred_probe_add_trigger(dev, local_trigger_count);
done:
- atomic_dec(&probe_count);
- wake_up_all(&probe_waitqueue);
return ret;
}

@@ -739,21 +721,7 @@ void wait_for_device_probe(void)
}
EXPORT_SYMBOL_GPL(wait_for_device_probe);

-/**
- * driver_probe_device - attempt to bind device & driver together
- * @drv: driver to bind a device to
- * @dev: device to try to bind to the driver
- *
- * This function returns -ENODEV if the device is not registered, -EBUSY if it
- * already has a driver, 0 if the device is bound successfully and a positive
- * (inverted) error code for failures from the ->probe method.
- *
- * This function must be called with @dev lock held. When called for a
- * USB interface, @dev->parent lock must be held as well.
- *
- * If the device has a parent, runtime-resume the parent before driver probing.
- */
-static int driver_probe_device(struct device_driver *drv, struct device *dev)
+static int __driver_probe_device(struct device_driver *drv, struct device *dev)
{
int ret = 0;

@@ -784,6 +752,42 @@ static int driver_probe_device(struct device_driver *drv, struct device *dev)
return ret;
}

+/**
+ * driver_probe_device - attempt to bind device & driver together
+ * @drv: driver to bind a device to
+ * @dev: device to try to bind to the driver
+ *
+ * This function returns -ENODEV if the device is not registered, -EBUSY if it
+ * already has a driver, 0 if the device is bound successfully and a positive
+ * (inverted) error code for failures from the ->probe method.
+ *
+ * This function must be called with @dev lock held. When called for a
+ * USB interface, @dev->parent lock must be held as well.
+ *
+ * If the device has a parent, runtime-resume the parent before driver probing.
+ */
+static int driver_probe_device(struct device_driver *drv, struct device *dev)
+{
+ int trigger_count = atomic_read(&deferred_trigger_count);
+ int ret;
+
+ atomic_inc(&probe_count);
+ ret = __driver_probe_device(drv, dev);
+ if (ret == -EPROBE_DEFER || ret == EPROBE_DEFER) {
+ driver_deferred_probe_add(dev);
+
+ /*
+ * Did a trigger occur while probing? Need to re-trigger if yes
+ */
+ if (trigger_count != atomic_read(&deferred_trigger_count) &&
+ !defer_all_probes)
+ driver_deferred_probe_trigger();
+ }
+ atomic_dec(&probe_count);
+ wake_up_all(&probe_waitqueue);
+ return ret;
+}
+
static inline bool cmdline_requested_async_probing(const char *drv_name)
{
return parse_option_str(async_probe_drv_names, drv_name);
@@ -1051,12 +1055,14 @@ int device_driver_attach(struct device_driver *drv, struct device *dev)
int ret;

__device_driver_lock(dev, dev->parent);
- ret = driver_probe_device(drv, dev);
+ ret = __driver_probe_device(drv, dev);
__device_driver_unlock(dev, dev->parent);

/* also return probe errors as normal negative errnos */
if (ret > 0)
ret = -ret;
+ if (ret == -EPROBE_DEFER)
+ return -EAGAIN;
return ret;
}

--
2.30.2