iavf: Fix use-after-free in free_netdev

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

iavf: Fix use-after-free in free_netdev

We do netif_napi_add() for all allocated q_vectors[], but potentially
do netif_napi_del() for part of them, then kfree q_vectors and leave
invalid pointers at dev->napi_list.

Reproducer:

[root@host ~]# cat repro.sh
#!/bin/bash

pf_dbsf="0000:41:00.0"
vf0_dbsf="0000:41:02.0"
g_pids=()

function do_set_numvf()
{
echo 2 >/sys/bus/pci/devices/${pf_dbsf}/sriov_numvfs
sleep $((RANDOM%3+1))
echo 0 >/sys/bus/pci/devices/${pf_dbsf}/sriov_numvfs
sleep $((RANDOM%3+1))
}

function do_set_channel()
{
local nic=$(ls -1 --indicator-style=none /sys/bus/pci/devices/${vf0_dbsf}/net/)
[ -z "$nic" ] && { sleep $((RANDOM%3)) ; return 1; }
ifconfig $nic 192.168.18.5 netmask 255.255.255.0
ifconfig $nic up
ethtool -L $nic combined 1
ethtool -L $nic combined 4
sleep $((RANDOM%3))
}

function on_exit()
{
local pid
for pid in "${g_pids[@]}"; do
kill -0 "$pid" &>/dev/null && kill "$pid" &>/dev/null
done
g_pids=()
}

trap "on_exit; exit" EXIT

while :; do do_set_numvf ; done &
g_pids+=($!)
while :; do do_set_channel ; done &
g_pids+=($!)

wait

Result:

[ 4093.900222] ==================================================================
[ 4093.900230] BUG: KASAN: use-after-free in free_netdev+0x308/0x390
[ 4093.900232] Read of size 8 at addr ffff88b4dc145640 by task repro.sh/6699
[ 4093.900233]
[ 4093.900236] CPU: 10 PID: 6699 Comm: repro.sh Kdump: loaded Tainted: G O --------- -t - 4.18.0 #1
[ 4093.900238] Hardware name: Powerleader PR2008AL/H12DSi-N6, BIOS 2.0 04/09/2021
[ 4093.900239] Call Trace:
[ 4093.900244] dump_stack+0x71/0xab
[ 4093.900249] print_address_description+0x6b/0x290
[ 4093.900251] ? free_netdev+0x308/0x390
[ 4093.900252] kasan_report+0x14a/0x2b0
[ 4093.900254] free_netdev+0x308/0x390
[ 4093.900261] iavf_remove+0x825/0xd20 [iavf]
[ 4093.900265] pci_device_remove+0xa8/0x1f0
[ 4093.900268] device_release_driver_internal+0x1c6/0x460
[ 4093.900271] pci_stop_bus_device+0x101/0x150
[ 4093.900273] pci_stop_and_remove_bus_device+0xe/0x20
[ 4093.900275] pci_iov_remove_virtfn+0x187/0x420
[ 4093.900277] ? pci_iov_add_virtfn+0xe10/0xe10
[ 4093.900278] ? pci_get_subsys+0x90/0x90
[ 4093.900280] sriov_disable+0xed/0x3e0
[ 4093.900282] ? bus_find_device+0x12d/0x1a0
[ 4093.900290] i40e_free_vfs+0x754/0x1210 [i40e]
[ 4093.900298] ? i40e_reset_all_vfs+0x880/0x880 [i40e]
[ 4093.900299] ? pci_get_device+0x7c/0x90
[ 4093.900300] ? pci_get_subsys+0x90/0x90
[ 4093.900306] ? pci_vfs_assigned.part.7+0x144/0x210
[ 4093.900309] ? __mutex_lock_slowpath+0x10/0x10
[ 4093.900315] i40e_pci_sriov_configure+0x1fa/0x2e0 [i40e]
[ 4093.900318] sriov_numvfs_store+0x214/0x290
[ 4093.900320] ? sriov_totalvfs_show+0x30/0x30
[ 4093.900321] ? __mutex_lock_slowpath+0x10/0x10
[ 4093.900323] ? __check_object_size+0x15a/0x350
[ 4093.900326] kernfs_fop_write+0x280/0x3f0
[ 4093.900329] vfs_write+0x145/0x440
[ 4093.900330] ksys_write+0xab/0x160
[ 4093.900332] ? __ia32_sys_read+0xb0/0xb0
[ 4093.900334] ? fput_many+0x1a/0x120
[ 4093.900335] ? filp_close+0xf0/0x130
[ 4093.900338] do_syscall_64+0xa0/0x370
[ 4093.900339] ? page_fault+0x8/0x30
[ 4093.900341] entry_SYSCALL_64_after_hwframe+0x65/0xca
[ 4093.900357] RIP: 0033:0x7f16ad4d22c0
[ 4093.900359] Code: 73 01 c3 48 8b 0d d8 cb 2c 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 83 3d 89 24 2d 00 00 75 10 b8 01 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 fe dd 01 00 48 89 04 24
[ 4093.900360] RSP: 002b:00007ffd6491b7f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
[ 4093.900362] RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007f16ad4d22c0
[ 4093.900363] RDX: 0000000000000002 RSI: 0000000001a41408 RDI: 0000000000000001
[ 4093.900364] RBP: 0000000001a41408 R08: 00007f16ad7a1780 R09: 00007f16ae1f2700
[ 4093.9003
---truncated---