[PATCH 4/6] rpmsg: Fix calling device_lock() on non-initialized device

[Lee Jones <lee@kernel.org>]

From: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

commit bb17d110cbf270d5247a6e261c5ad50e362d1675 upstream.

driver_set_override() helper uses device_lock() so it should not be
called before rpmsg_register_device() (which calls device_register()).
Effect can be seen with CONFIG_DEBUG_MUTEXES:

  DEBUG_LOCKS_WARN_ON(lock->magic != lock)
  WARNING: CPU: 3 PID: 57 at kernel/locking/mutex.c:582 __mutex_lock+0x1ec/0x430
  ...
  Call trace:
   __mutex_lock+0x1ec/0x430
   mutex_lock_nested+0x44/0x50
   driver_set_override+0x124/0x150
   qcom_glink_native_probe+0x30c/0x3b0
   glink_rpm_probe+0x274/0x350
   platform_probe+0x6c/0xe0
   really_probe+0x17c/0x3d0
   __driver_probe_device+0x114/0x190
   driver_probe_device+0x3c/0xf0
   ...

Refactor the rpmsg_register_device() function to use two-step device
registering (initialization + add) and call driver_set_override() in
proper moment.

This moves the code around, so while at it also NULL-ify the
rpdev->driver_override in error path to be sure it won't be kfree()
second time.

Fixes: 42cd402b8fd4 ("rpmsg: Fix kfree() of static memory on setting driver_override")
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/r/20220429195946.1061725-2-krzysztof.kozlowski@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Lee Jones <lee@kernel.org>
Change-Id: I37c19feae515b3721a0013615d47886a7b1108de
---
 drivers/rpmsg/rpmsg_core.c     | 33 ++++++++++++++++++++++++++++++---
 drivers/rpmsg/rpmsg_internal.h | 14 +-------------
 drivers/rpmsg/rpmsg_ns.c       |  4 +---
 include/linux/rpmsg.h          |  8 ++++++++
 4 files changed, 40 insertions(+), 19 deletions(-)

diff --git a/drivers/rpmsg/rpmsg_core.c b/drivers/rpmsg/rpmsg_core.c
index c544dee0b5dd9..0ea8f8ec84efc 100644
--- a/drivers/rpmsg/rpmsg_core.c
+++ b/drivers/rpmsg/rpmsg_core.c
@@ -569,24 +569,51 @@ static struct bus_type rpmsg_bus = {
 	.remove		= rpmsg_dev_remove,
 };
 
-int rpmsg_register_device(struct rpmsg_device *rpdev)
+/*
+ * A helper for registering rpmsg device with driver override and name.
+ * Drivers should not be using it, but instead rpmsg_register_device().
+ */
+int rpmsg_register_device_override(struct rpmsg_device *rpdev,
+				   const char *driver_override)
 {
 	struct device *dev = &rpdev->dev;
 	int ret;
 
+	if (driver_override)
+		strcpy(rpdev->id.name, driver_override);
+
 	dev_set_name(&rpdev->dev, "%s.%s.%d.%d", dev_name(dev->parent),
 		     rpdev->id.name, rpdev->src, rpdev->dst);
 
 	rpdev->dev.bus = &rpmsg_bus;
 
-	ret = device_register(&rpdev->dev);
+	device_initialize(dev);
+	if (driver_override) {
+		ret = driver_set_override(dev, &rpdev->driver_override,
+					  driver_override,
+					  strlen(driver_override));
+		if (ret) {
+			dev_err(dev, "device_set_override failed: %d\n", ret);
+			return ret;
+		}
+	}
+
+	ret = device_add(dev);
 	if (ret) {
-		dev_err(dev, "device_register failed: %d\n", ret);
+		dev_err(dev, "device_add failed: %d\n", ret);
+		kfree(rpdev->driver_override);
+		rpdev->driver_override = NULL;
 		put_device(&rpdev->dev);
 	}
 
 	return ret;
 }
+EXPORT_SYMBOL(rpmsg_register_device_override);
+
+int rpmsg_register_device(struct rpmsg_device *rpdev)
+{
+	return rpmsg_register_device_override(rpdev, NULL);
+}
 EXPORT_SYMBOL(rpmsg_register_device);
 
 /*
diff --git a/drivers/rpmsg/rpmsg_internal.h b/drivers/rpmsg/rpmsg_internal.h
index 5f4f3691bbf1e..7985af92aa489 100644
--- a/drivers/rpmsg/rpmsg_internal.h
+++ b/drivers/rpmsg/rpmsg_internal.h
@@ -90,19 +90,7 @@ int rpmsg_release_channel(struct rpmsg_device *rpdev,
  */
 static inline int rpmsg_chrdev_register_device(struct rpmsg_device *rpdev)
 {
-	int ret;
-
-	strcpy(rpdev->id.name, "rpmsg_chrdev");
-	ret = driver_set_override(&rpdev->dev, &rpdev->driver_override,
-				  rpdev->id.name, strlen(rpdev->id.name));
-	if (ret)
-		return ret;
-
-	ret = rpmsg_register_device(rpdev);
-	if (ret)
-		kfree(rpdev->driver_override);
-
-	return ret;
+	return rpmsg_register_device_override(rpdev, "rpmsg_ctrl");
 }
 
 #endif
diff --git a/drivers/rpmsg/rpmsg_ns.c b/drivers/rpmsg/rpmsg_ns.c
index 762ff1ae279f2..c70ad03ff2e90 100644
--- a/drivers/rpmsg/rpmsg_ns.c
+++ b/drivers/rpmsg/rpmsg_ns.c
@@ -20,12 +20,10 @@
  */
 int rpmsg_ns_register_device(struct rpmsg_device *rpdev)
 {
-	strcpy(rpdev->id.name, "rpmsg_ns");
-	rpdev->driver_override = "rpmsg_ns";
 	rpdev->src = RPMSG_NS_ADDR;
 	rpdev->dst = RPMSG_NS_ADDR;
 
-	return rpmsg_register_device(rpdev);
+	return rpmsg_register_device_override(rpdev, "rpmsg_ns");
 }
 EXPORT_SYMBOL(rpmsg_ns_register_device);
 
diff --git a/include/linux/rpmsg.h b/include/linux/rpmsg.h
index 1b7294cefb807..a63c5a4ff3e15 100644
--- a/include/linux/rpmsg.h
+++ b/include/linux/rpmsg.h
@@ -165,6 +165,8 @@ static inline __rpmsg64 cpu_to_rpmsg64(struct rpmsg_device *rpdev, u64 val)
 
 #if IS_ENABLED(CONFIG_RPMSG)
 
+int rpmsg_register_device_override(struct rpmsg_device *rpdev,
+				   const char *driver_override);
 int rpmsg_register_device(struct rpmsg_device *rpdev);
 int rpmsg_unregister_device(struct device *parent,
 			    struct rpmsg_channel_info *chinfo);
@@ -190,6 +192,12 @@ __poll_t rpmsg_poll(struct rpmsg_endpoint *ept, struct file *filp,
 
 #else
 
+static inline int rpmsg_register_device_override(struct rpmsg_device *rpdev,
+						 const char *driver_override)
+{
+	return -ENXIO;
+}
+
 static inline int rpmsg_register_device(struct rpmsg_device *rpdev)
 {
 	return -ENXIO;
-- 
2.42.0.820.g83a721a137-goog