Re: [PATCH V1 1/3] rpmsg: glink: Free device context only when cdev not in use

Deepak Kumar Singh
2022-02-14T15:02:43Z

On 2/3/2022 11:05 PM, Mathieu Poirier wrote:
> Hi Deepak,
>
> On Thu, Jan 27, 2022 at 12:34:44AM +0530, Deepak Kumar Singh wrote:
>> Struct device holding cdev should not be freed unless cdev
>> is not in use. It is possible that user space has opened
>> char device while kernel has freed the associated struct
>> device context.
>>
>> Mark dev kobj as parent of cdev, so that chardev_add gets
>> an extra reference to dev. This ensures device context is not
>> freed until cdev is is not in uses.
>> ---
>> drivers/rpmsg/rpmsg_char.c | 2 ++
>> 1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/rpmsg/rpmsg_char.c b/drivers/rpmsg/rpmsg_char.c
>> index c03a118..72ee101 100644
>> --- a/drivers/rpmsg/rpmsg_char.c
>> +++ b/drivers/rpmsg/rpmsg_char.c
>> @@ -417,6 +417,7 @@ static int rpmsg_eptdev_create(struct rpmsg_ctrldev *ctrldev,
>> dev->id = ret;
>> dev_set_name(dev, "rpmsg%d", ret);
>>
>> + cdev_set_parent(&eptdev->cdev, &dev->kobj);
>> ret = cdev_add(&eptdev->cdev, dev->devt, 1);
> This issue should have been fixed when cdev_add() was replaced by
> cdev_device_add(), something you will find on v5.17-rc2.
>
> Also, this set is generating checkpatch warnings and as such I will not review
> the other patches in it.
>
> Thanks,
> Mathieu

Thank you Mathieu for info!! i will recheck other 2 patches for
checkpatch warnings.

Thanks,

Deepak

>> if (ret)
>> goto free_ept_ida;
>> @@ -533,6 +534,7 @@ static int rpmsg_chrdev_probe(struct rpmsg_device *rpdev)
>> dev->id = ret;
>> dev_set_name(&ctrldev->dev, "rpmsg_ctrl%d", ret);
>>
>> + cdev_set_parent(&ctrldev->cdev, &dev->kobj);
>> ret = cdev_add(&ctrldev->cdev, dev->devt, 1);
>> if (ret)
>> goto free_ctrl_ida;
>> --
>> 2.7.4
>>