[PATCH] mshv_vtl: Release mem_dev through put_device()

[PATCH] mshv_vtl: Release mem_dev through put_device()

[Suyuan Wang via B4 Relay]

From: Suyuan Wang <stevewong@hust.edu.cn>

mem_dev is set up with device_initialize() and device_add(), but it is
freed with a plain kfree(), both on the device_add() error path and on
module exit:

    device_del(mem_dev);
    kfree(mem_dev);

It has no release() callback either. Freeing an initialized device with
kfree() skips the final put_device() and device_release(). On module
unload this leaks the device name and the device_private allocated by
device_add(), and on the device_add() error path at least the name is
leaked. The leak is small, and the fix is to free the device the way
the driver core expects.

Give mem_dev a release() callback that frees it, and use put_device()
on the error path and device_unregister() in mshv_vtl_exit(). Nothing
else changes: the devm_memremap_pages() mapping is still torn down by
device_del() as before.

Found with a static analysis tool and checked by hand.

Fixes: 7bfe3b8ea6e3 ("Drivers: hv: Introduce mshv_vtl driver")
Cc: stable@vger.kernel.org
Co-developed-by: Kaixuan Li <kaixuan.li@ntu.edu.sg>
Signed-off-by: Kaixuan Li <kaixuan.li@ntu.edu.sg>
Signed-off-by: Suyuan Wang <stevewong@hust.edu.cn>
---
Compile tested with CONFIG_MSHV_VTL=y only, I don't have an OpenHCL
setup to run it.
---
 drivers/hv/mshv_vtl_main.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/hv/mshv_vtl_main.c b/drivers/hv/mshv_vtl_main.c
index 2d4fe24cecbf..bbf43330e129 100644
--- a/drivers/hv/mshv_vtl_main.c
+++ b/drivers/hv/mshv_vtl_main.c
@@ -1346,6 +1346,11 @@ static struct miscdevice mshv_vtl_low = {
 	.minor = MISC_DYNAMIC_MINOR,
 };
 
+static void mshv_vtl_mem_dev_release(struct device *dev)
+{
+	kfree(dev);
+}
+
 static int __init mshv_vtl_init(void)
 {
 	int ret;
@@ -1412,17 +1417,18 @@ static int __init mshv_vtl_init(void)
 	}
 
 	device_initialize(mem_dev);
+	mem_dev->release = mshv_vtl_mem_dev_release;
 	dev_set_name(mem_dev, "mshv vtl mem dev");
 	ret = device_add(mem_dev);
 	if (ret) {
 		dev_err(dev, "mshv vtl mem dev add: %d\n", ret);
-		goto free_mem;
+		goto put_mem;
 	}
 
 	return 0;
 
-free_mem:
-	kfree(mem_dev);
+put_mem:
+	put_device(mem_dev);
 free_low:
 	misc_deregister(&mshv_vtl_low);
 free_hvcall:
@@ -1439,8 +1445,7 @@ static int __init mshv_vtl_init(void)
 
 static void __exit mshv_vtl_exit(void)
 {
-	device_del(mem_dev);
-	kfree(mem_dev);
+	device_unregister(mem_dev);
 	misc_deregister(&mshv_vtl_low);
 	misc_deregister(&mshv_vtl_hvcall_dev);
 	misc_deregister(&mshv_vtl_sint_dev);

---
base-commit: 630059a5a632377b9b7b487baccde92b7ae1dd47
change-id: 20261112-hyperv-55c5333ce654

Best regards,
--  
Suyuan Wang <shyckless@gmail.com>