> From: Jason Gunthorpe <jgg@xxxxxxxxxx>
> Sent: Wednesday, March 24, 2021 1:55 AM
>
> There is a small race where the parent is NULL even though the kobj has
> already been made visible in sysfs.
>
> For instance the attribute_group is made visible in sysfs_create_files()
> and the mdev_type_attr_show() does:
>
> ret = attr->show(kobj, type->parent->dev, buf);
>
> Which will crash on NULL parent. Move the parent setup to before the type
> pointer leaves the stack frame.
>
> Fixes: 7b96953bc640 ("vfio: Mediated device Core driver")
> Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
> ---
> drivers/vfio/mdev/mdev_sysfs.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/vfio/mdev/mdev_sysfs.c
> b/drivers/vfio/mdev/mdev_sysfs.c
> index 321b4d13ead7b8..5219cdd6dbbc49 100644
> --- a/drivers/vfio/mdev/mdev_sysfs.c
> +++ b/drivers/vfio/mdev/mdev_sysfs.c
> @@ -105,6 +105,7 @@ static struct mdev_type
> *add_mdev_supported_type(struct mdev_parent *parent,
> return ERR_PTR(-ENOMEM);
>
> type->kobj.kset = parent->mdev_types_kset;
> + type->parent = parent;
>
> ret = kobject_init_and_add(&type->kobj, &mdev_type_ktype, NULL,
> "%s-%s", dev_driver_string(parent->dev),
> @@ -132,7 +133,6 @@ static struct mdev_type
> *add_mdev_supported_type(struct mdev_parent *parent,
> }
>
> type->group = group;
> - type->parent = parent;
> return type;
>
> attrs_failed:
> --
> 2.31.0
