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    SubjectRe: [PATCH v5 04/13] s390: vfio-ap: base implementation of VFIO AP device driver
    On Wed, 13 Jun 2018 09:41:16 +0200
    Pierre Morel <pmorel@linux.ibm.com> wrote:

    > On 07/05/2018 17:11, Tony Krowiak wrote:
    > > Introduces a new AP device driver. This device driver
    > > is built on the VFIO mediated device framework. The framework
    > > provides sysfs interfaces that facilitate passthrough
    > > access by guests to devices installed on the linux host.
    > ...snip...
    >
    > > +static int vfio_ap_matrix_dev_create(void)
    > > +{
    > > + int ret;
    > > +
    > > + vfio_ap_root_device = root_device_register(VFIO_AP_ROOT_NAME);
    > > +
    > > + if (IS_ERR(vfio_ap_root_device)) {
    > > + ret = PTR_ERR(vfio_ap_root_device);
    > > + goto done;
    > > + }
    > > +
    > > + ap_matrix = kzalloc(sizeof(*ap_matrix), GFP_KERNEL);
    > > + if (!ap_matrix) {
    > > + ret = -ENOMEM;
    > > + goto matrix_alloc_err;
    > > + }
    > > +
    > > + ap_matrix->device.type = &vfio_ap_dev_type;
    > > + dev_set_name(&ap_matrix->device, "%s", VFIO_AP_DEV_NAME);
    > > + ap_matrix->device.parent = vfio_ap_root_device;
    > > + ap_matrix->device.release = vfio_ap_matrix_dev_release;
    > > + ap_matrix->device.driver = &vfio_ap_drv.driver;
    > > +
    > > + ret = device_register(&ap_matrix->device);
    > > + if (ret)
    > > + goto matrix_reg_err;
    > > +
    > > + goto done;
    > > +
    > > +matrix_reg_err:
    > > + put_device(&ap_matrix->device);
    >
    > Did not see this before but here you certainly want to
    > do a kfree and not a put_device.

    No, this must not be a kfree. Once you've tried to register something
    embedding a struct device with the driver core, you need to use
    put_device, as another path may have acquired a reference, even if
    registering ultimately failed. See the comment for device_register().
    IOW, the code is correct.

    >
    >
    >
    > > +
    > > +matrix_alloc_err:
    > > + root_device_unregister(vfio_ap_root_device);
    > > +
    > > +done:
    > > + return ret;
    > > +}
    > > +
    > > +static void vfio_ap_matrix_dev_destroy(struct ap_matrix *ap_matrix)
    > > +{
    > > + device_unregister(&ap_matrix->device);
    > > + root_device_unregister(vfio_ap_root_device);
    >
    > Also here you need a kfree(ap_matrix) too .

    Same here.

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