vdpa: Add features attr to vdpa_nl_policy for nlattr length check

vdpa: Add features attr to vdpa_nl_policy for nlattr length check

The vdpa_nl_policy structure is used to validate the nlattr when parsing
the incoming nlmsg. It will ensure the attribute being described produces
a valid nlattr pointer in info->attrs before entering into each handler
in vdpa_nl_ops.

That is to say, the missing part in vdpa_nl_policy may lead to illegal
nlattr after parsing, which could lead to OOB read just like CVE-2023-3773.

This patch adds the missing nla_policy for vdpa features attr to avoid
such bugs.

Fixes: 90fea5a800c3 ("vdpa: device feature provisioning")
Signed-off-by: Lin Ma <linma@zju.edu.cn>
Cc: stable@vger.kernel.org
Message-Id: <20230727175757.73988-3-dtatulea@nvidia.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>