[PATCH 1/3] device-dax: Prevent registering drivers without probe or remove callback

[PATCH 1/3] device-dax: Prevent registering drivers without probe or remove callback

[Uwe Kleine-König]

The bus probe and remove functions (dax_bus_probe and dax_bus_remove
respectively) call these functions without checking them to be non-NULL.
Add a check to prevent a NULL pointer exception.

Signed-off-by: Uwe Kleine-König <uwe@kleine-koenig.org>
---
 drivers/dax/bus.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index 737b207c9e30..618d462975ba 100644
--- a/drivers/dax/bus.c
+++ b/drivers/dax/bus.c
@@ -1392,6 +1392,14 @@ int __dax_driver_register(struct dax_device_driver *dax_drv,
 	struct device_driver *drv = &dax_drv->drv;
 	int rc = 0;
 
+	/*
+	 * dax_bus_probe() calls dax_drv->probe() unconditionally and
+	 * dax_bus_remove() calls dax_drv->remove() unconditionally. So better
+	 * be safe than sorry and ensure these are provided.
+	 */
+	if (!dax_drv->probe || !dax_drv->remove)
+		return -EINVAL;
+
 	INIT_LIST_HEAD(&dax_drv->ids);
 	drv->owner = module;
 	drv->name = mod_name;

base-commit: 5c8fe583cce542aa0b84adc939ce85293de36e5e
-- 
2.29.2
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[PATCH 2/3] dax-device: Fix error path in dax_driver_register

[Uwe Kleine-König]

The static variable match_always_count is supposed to track if there is
a driver registered that has .match_always set. If driver_register()
fails, the previous increment must be undone.

Signed-off-by: Uwe Kleine-König <uwe@kleine-koenig.org>
---
 drivers/dax/bus.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index 618d462975ba..498c60333d60 100644
--- a/drivers/dax/bus.c
+++ b/drivers/dax/bus.c
@@ -1417,7 +1417,15 @@ int __dax_driver_register(struct dax_device_driver *dax_drv,
 	mutex_unlock(&dax_bus_lock);
 	if (rc)
 		return rc;
-	return driver_register(drv);
+
+	rc = driver_register(drv);
+	if (rc && dax_drv->match_always) {
+		mutex_lock(&dax_bus_lock);
+		match_always_count -= dax_drv->match_always;
+		mutex_unlock(&dax_bus_lock);
+	}
+
+	return rc;
 }
 EXPORT_SYMBOL_GPL(__dax_driver_register);
 
-- 
2.29.2
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[PATCH 3/3] dax-device: Make remove callback return void

[Uwe Kleine-König]

The driver core ignores the return value of struct bus_type::remove()
because there is only little that can be done. To simplify the quest to
make this function return void, let struct dax_device_driver::remove()
return void, too. All users already unconditionally return 0, this commit
makes it obvious that returning an error code is a bad idea and makes it
obvious for future driver authors that returning an error code isn't
intended.

Signed-off-by: Uwe Kleine-König <uwe@kleine-koenig.org>
---
 drivers/dax/bus.c    | 4 +++-
 drivers/dax/bus.h    | 2 +-
 drivers/dax/device.c | 3 +--
 drivers/dax/kmem.c   | 7 ++-----
 4 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index 498c60333d60..253f37a61371 100644
--- a/drivers/dax/bus.c
+++ b/drivers/dax/bus.c
@@ -179,7 +179,9 @@ static int dax_bus_remove(struct device *dev)
 	struct dax_device_driver *dax_drv = to_dax_drv(dev->driver);
 	struct dev_dax *dev_dax = to_dev_dax(dev);
 
-	return dax_drv->remove(dev_dax);
+	dax_drv->remove(dev_dax);
+
+	return 0;
 }
 
 static struct bus_type dax_bus_type = {
diff --git a/drivers/dax/bus.h b/drivers/dax/bus.h
index 72b92f95509f..1e946ad7780a 100644
--- a/drivers/dax/bus.h
+++ b/drivers/dax/bus.h
@@ -39,7 +39,7 @@ struct dax_device_driver {
 	struct list_head ids;
 	int match_always;
 	int (*probe)(struct dev_dax *dev);
-	int (*remove)(struct dev_dax *dev);
+	void (*remove)(struct dev_dax *dev);
 };
 
 int __dax_driver_register(struct dax_device_driver *dax_drv,
diff --git a/drivers/dax/device.c b/drivers/dax/device.c
index 5da2980bb16b..d532c885f574 100644
--- a/drivers/dax/device.c
+++ b/drivers/dax/device.c
@@ -452,10 +452,9 @@ int dev_dax_probe(struct dev_dax *dev_dax)
 }
 EXPORT_SYMBOL_GPL(dev_dax_probe);
 
-static int dev_dax_remove(struct dev_dax *dev_dax)
+static void dev_dax_remove(struct dev_dax *dev_dax)
 {
 	/* all probe actions are unwound by devm */
-	return 0;
 }
 
 static struct dax_device_driver device_dax_driver = {
diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
index 403ec42472d1..ac231cc36359 100644
--- a/drivers/dax/kmem.c
+++ b/drivers/dax/kmem.c
@@ -136,7 +136,7 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
 }
 
 #ifdef CONFIG_MEMORY_HOTREMOVE
-static int dev_dax_kmem_remove(struct dev_dax *dev_dax)
+static void dev_dax_kmem_remove(struct dev_dax *dev_dax)
 {
 	int i, success = 0;
 	struct device *dev = &dev_dax->dev;
@@ -176,11 +176,9 @@ static int dev_dax_kmem_remove(struct dev_dax *dev_dax)
 		kfree(data);
 		dev_set_drvdata(dev, NULL);
 	}
-
-	return 0;
 }
 #else
-static int dev_dax_kmem_remove(struct dev_dax *dev_dax)
+static void dev_dax_kmem_remove(struct dev_dax *dev_dax)
 {
 	/*
 	 * Without hotremove purposely leak the request_mem_region() for the
@@ -190,7 +188,6 @@ static int dev_dax_kmem_remove(struct dev_dax *dev_dax)
 	 * request_mem_region().
 	 */
 	any_hotremove_failed = true;
-	return 0;
 }
 #endif /* CONFIG_MEMORY_HOTREMOVE */
 
-- 
2.29.2
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