From: Jason Gunthorpe <jgg@nvidia.com> stable inclusion from linux-4.19.191 commit 6af3de26ee2b42ff5104a0a0f048df82e37fbc82 -------------------------------- [ Upstream commit b5a1f8921d5040bb788492bf33a66758021e4be5 ] 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") Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Kevin Tian <kevin.tian@intel.com> Reviewed-by: Max Gurtovoy <mgurtovoy@nvidia.com> Reviewed-by: Cornelia Huck <cohuck@redhat.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com> Message-Id: <2-v2-d36939638fc6+d54-vfio2_jgg@nvidia.com> Signed-off-by: Alex Williamson <alex.williamson@redhat.com> Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> --- 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 1692a0cc30360..c99fcc6c2eba8 100644 --- a/drivers/vfio/mdev/mdev_sysfs.c +++ b/drivers/vfio/mdev/mdev_sysfs.c @@ -108,6 +108,7 @@ 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), @@ -135,7 +136,6 @@ struct mdev_type *add_mdev_supported_type(struct mdev_parent *parent, } type->group = group; - type->parent = parent; return type; attrs_failed: -- 2.25.1