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vfio/mdev: Do not allow a mdev_type to have a NULL parent pointer 

[ 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: 7b96953bc6 ("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>
This commit is contained in:
Jason Gunthorpe 2021-04-06 16:40:25 -03:00 committed by Greg Kroah-Hartman
parent e6707395c8
commit 3d81ce0cfb
1 changed files with 1 additions and 1 deletions
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2
drivers/vfio/mdev/mdev_sysfs.c
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@ -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: