virtio_net: fix xdp_rxq_info bug after suspend/resume

In the Linux kernel, the following vulnerability has been resolved:

virtio_net: fix xdp_rxq_info bug after suspend/resume

The following sequence currently causes a driver bug warning

when using virtio_net:

# ip link set eth0 up

# echo mem > /sys/power/state (or e.g. # rtcwake -s 10 -m mem)

<resume>

# ip link set eth0 down

Missing register, driver bug

WARNING: CPU: 0 PID: 375 at net/core/xdp.c:138 xdp_rxq_info_unreg+0x58/0x60

Call trace:

xdp_rxq_info_unreg+0x58/0x60

virtnet_close+0x58/0xac

__dev_close_many+0xac/0x140

__dev_change_flags+0xd8/0x210

dev_change_flags+0x24/0x64

do_setlink+0x230/0xdd0

...

This happens because virtnet_freeze() frees the receive_queue

completely (including struct xdp_rxq_info) but does not call

xdp_rxq_info_unreg(). Similarly, virtnet_restore() sets up the

receive_queue again but does not call xdp_rxq_info_reg().

Actually, parts of virtnet_freeze_down() and virtnet_restore_up()

are almost identical to virtnet_close() and virtnet_open(): only

the calls to xdp_rxq_info_(un)reg() are missing. This means that

we can fix this easily and avoid such problems in the future by

just calling virtnet_close()/open() from the freeze/restore handlers.

Aside from adding the missing xdp_rxq_info calls the only difference

is that the refill work is only cancelled if netif_running(). However,

this should not make any functional difference since the refill work

should only be active if the network interface is actually up.