vdpa: Read device configuration only if FEATURES_OK

mainline inclusion
from mainline-v5.17-rc1
commit 30ef7a8a
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5WXCZ
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=30ef7a8ac8a07046b9ac9206d3a732a9f76b2e60



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Avoid reading device configuration during feature negotiation. Read
device status and verify that VIRTIO_CONFIG_S_FEATURES_OK is set.

Protect the entire operation, including configuration read with cf_mutex
to ensure integrity of the results.

Signed-off-by: Eli Cohen <elic@nvidia.com>
Link: https://lore.kernel.org/r/20220105114646.577224-5-elic@nvidia.com


Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Pengyuan Zhao <zhaopengyuan@hisilicon.com>