[PATCH v4.14.y 2/2] rpmsg: Fix kfree() of static memory on setting driver_override

[Lee Jones <lee@kernel.org>]

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

commit 42cd402b8fd4672b692400fe5f9eecd55d2794ac upstream.

The driver_override field from platform driver should not be initialized
from static memory (string literal) because the core later kfree() it,
for example when driver_override is set via sysfs.

Use dedicated helper to set driver_override properly.

Fixes: 950a7388f02b ("rpmsg: Turn name service into a stand alone driver")
Fixes: c0cdc19f84a4 ("rpmsg: Driver for user space endpoint interface")
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220419113435.246203-13-krzysztof.kozlowski@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Lee Jones <lee@kernel.org>
---
 drivers/rpmsg/rpmsg_internal.h | 13 +++++++++++--
 include/linux/rpmsg.h          |  6 ++++--
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/rpmsg/rpmsg_internal.h b/drivers/rpmsg/rpmsg_internal.h
index 0cf9c7e2ee835..e1522caadbc8a 100644
--- a/drivers/rpmsg/rpmsg_internal.h
+++ b/drivers/rpmsg/rpmsg_internal.h
@@ -91,10 +91,19 @@ struct device *rpmsg_find_device(struct device *parent,
  */
 static inline int rpmsg_chrdev_register_device(struct rpmsg_device *rpdev)
 {
+	int ret;
+
 	strcpy(rpdev->id.name, "rpmsg_chrdev");
-	rpdev->driver_override = "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 rpmsg_register_device(rpdev);
+	return ret;
 }
 
 #endif
diff --git a/include/linux/rpmsg.h b/include/linux/rpmsg.h
index 1ab79e8dc0b8f..fdbb7814cfbe8 100644
--- a/include/linux/rpmsg.h
+++ b/include/linux/rpmsg.h
@@ -66,7 +66,9 @@ struct rpmsg_channel_info {
  * rpmsg_device - device that belong to the rpmsg bus
  * @dev: the device struct
  * @id: device id (used to match between rpmsg drivers and devices)
- * @driver_override: driver name to force a match
+ * @driver_override: driver name to force a match; do not set directly,
+ *                   because core frees it; use driver_set_override() to
+ *                   set or clear it.
  * @src: local address
  * @dst: destination address
  * @ept: the rpmsg endpoint of this channel
@@ -75,7 +77,7 @@ struct rpmsg_channel_info {
 struct rpmsg_device {
 	struct device dev;
 	struct rpmsg_device_id id;
-	char *driver_override;
+	const char *driver_override;
 	u32 src;
 	u32 dst;
 	struct rpmsg_endpoint *ept;
-- 
2.42.0.655.g421f12c284-goog