On Fri, 2022-11-11 at 22:54 +0800, Yang Yingliang wrote:
> If device_register() fails in cxl_register_afu|adapter(), the device
> is not added, device_unregister() can not be called in the error
> path,
> otherwise it will cause a null-ptr-deref because of removing not
> added
> device.
>
> As comment of device_register() says, it should use put_device() to
> give
> up the reference in the error path. So split device_unregister() into
> device_del() and put_device(), then goes to put dev when register
> fails.
The comment around device_add() is relevant too:
Rule of thumb is: if device_add() succeeds, you should call
device_del() when you want to get rid of it. If device_add() has
*not* succeeded, use *only* put_device() to drop the reference count.
>
> Fixes: 14baf4d9c739 ("cxl: Add guest-specific code")
> Signed-off-by: Yang Yingliang <yangyingli...@huawei.com>
Thanks for the fix!
Acked-by: Andrew Donnellan <a...@linux.ibm.com>
> ---
> drivers/misc/cxl/guest.c | 24 ++++++++++++++----------
> 1 file changed, 14 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/misc/cxl/guest.c b/drivers/misc/cxl/guest.c
> index 375f692ae9d6..fb95a2d5cef4 100644
> --- a/drivers/misc/cxl/guest.c
> +++ b/drivers/misc/cxl/guest.c
> @@ -965,10 +965,10 @@ int cxl_guest_init_afu(struct cxl *adapter, int
> slice, struct device_node *afu_n
> * if it returns an error!
> */
> if ((rc = cxl_register_afu(afu)))
> - goto err_put1;
> + goto err_put_dev;
>
> if ((rc = cxl_sysfs_afu_add(afu)))
> - goto err_put1;
> + goto err_del_dev;
>
> /*
> * pHyp doesn't expose the programming models supported by
> the
> @@ -984,7 +984,7 @@ int cxl_guest_init_afu(struct cxl *adapter, int
> slice, struct device_node *afu_n
> afu->modes_supported = CXL_MODE_DIRECTED;
>
> if ((rc = cxl_afu_select_best_mode(afu)))
> - goto err_put2;
> + goto err_remove_sysfs;
>
> adapter->afu[afu->slice] = afu;
>
> @@ -1004,10 +1004,12 @@ int cxl_guest_init_afu(struct cxl *adapter,
> int slice, struct device_node *afu_n
>
> return 0;
>
> -err_put2:
> +err_remove_sysfs:
> cxl_sysfs_afu_remove(afu);
> -err_put1:
> - device_unregister(&afu->dev);
> +err_del_dev:
> + device_del(&afu->dev);
> +err_put_dev:
> + put_device(&afu->dev);
> free = false;
> guest_release_serr_irq(afu);
> err2:
> @@ -1141,18 +1143,20 @@ struct cxl *cxl_guest_init_adapter(struct
> device_node *np, struct platform_devic
> * even if it returns an error!
> */
> if ((rc = cxl_register_adapter(adapter)))
> - goto err_put1;
> + goto err_put_dev;
>
> if ((rc = cxl_sysfs_adapter_add(adapter)))
> - goto err_put1;
> + goto err_del_dev;
>
> /* release the context lock as the adapter is configured */
> cxl_adapter_context_unlock(adapter);
>
> return adapter;
>
> -err_put1:
> - device_unregister(&adapter->dev);
> +err_del_dev:
> + device_del(&adapter->dev);
> +err_put_dev:
> + put_device(&adapter->dev);
> free = false;
> cxl_guest_remove_chardev(adapter);
> err1:
--
Andrew Donnellan OzLabs, ADL Canberra
a...@linux.ibm.com IBM Australia Limited
