vfio/mdev: Do not allow a mdev_type to have a NULL parent pointer
authorJason Gunthorpe <jgg@nvidia.com>
Tue, 6 Apr 2021 19:40:25 +0000 (16:40 -0300)
committerAlex Williamson <alex.williamson@redhat.com>
Wed, 7 Apr 2021 21:39:16 +0000 (15:39 -0600)
commitb5a1f8921d5040bb788492bf33a66758021e4be5
tree409c68be592aa60d6e9f90328dbc0117ca442805
parent6cbf507fd08b52901d62bf11f3507e80f84c0db4
vfio/mdev: Do not allow a mdev_type to have a NULL parent pointer

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>
drivers/vfio/mdev/mdev_sysfs.c