Re: [PATCH] sparc: vio: use put_device() instead of kfree()

From: arvindY
Date: Wed Apr 25 2018 - 12:00:11 EST

On Wednesday 25 April 2018 09:14 PM, Shannon Nelson wrote:
On 4/25/2018 7:56 AM, Arvind Yadav wrote:
Never directly free @dev after calling device_register(), even
if it returned an error. Always use put_device() to give up the
reference initialized.

Signed-off-by: Arvind Yadav <arvind.yadav.cs@xxxxxxxxx>
arch/sparc/kernel/vio.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/sparc/kernel/vio.c b/arch/sparc/kernel/vio.c
index 1a0fa10..32bae68 100644
--- a/arch/sparc/kernel/vio.c
+++ b/arch/sparc/kernel/vio.c
@@ -403,7 +403,7 @@ static struct vio_dev *vio_create_one(struct mdesc_handle *hp, u64 mp,
if (err) {
printk(KERN_ERR "VIO: Could not register device %s, err=%d\n",
dev_name(&vdev->dev), err);
- kfree(vdev);
+ put_device(&vdev->dev);

Hmmm... I can see why the put_device() might be a good idea, but I think we still need the kfree() so as to not leak the memory that was kzalloc'd above for vdev.

There is no need to call kfree() here. Because put_device()
will decrement the last reference and then free the memory
by calling dev->release(It'll call vio_dev_release()).
Internally put_device() -> kobject_put() -> kobject_cleanup()
which is responsible to call 'dev -> release' and also free
other kobject resources.
If we will call kfree() here, Then It'll be a redundant call.



return NULL;
if (vdev->dp)