net: bonding: fix use-after-free after 802.3ad slave unbind

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

net: bonding: fix use-after-free after 802.3ad slave unbind

commit 0622cab0341c ("bonding: fix 802.3ad aggregator reselection"),
resolve case, when there is several aggregation groups in the same bond.
bond_3ad_unbind_slave will invalidate (clear) aggregator when
__agg_active_ports return zero. So, ad_clear_agg can be executed even, when
num_of_ports!=0. Than bond_3ad_unbind_slave can be executed again for,
previously cleared aggregator. NOTE: at this time bond_3ad_unbind_slave
will not update slave ports list, because lag_ports==NULL. So, here we
got slave ports, pointing to freed aggregator memory.

Fix with checking actual number of ports in group (as was before
commit 0622cab0341c ("bonding: fix 802.3ad aggregator reselection") ),
before ad_clear_agg().

The KASAN logs are as follows:

[ 767.617392] ==================================================================
[ 767.630776] BUG: KASAN: use-after-free in bond_3ad_state_machine_handler+0x13dc/0x1470
[ 767.638764] Read of size 2 at addr ffff00011ba9d430 by task kworker/u8:7/767
[ 767.647361] CPU: 3 PID: 767 Comm: kworker/u8:7 Tainted: G O 5.15.11 #15
[ 767.655329] Hardware name: DNI AmazonGo1 A7040 board (DT)
[ 767.660760] Workqueue: lacp_1 bond_3ad_state_machine_handler
[ 767.666468] Call trace:
[ 767.668930] dump_backtrace+0x0/0x2d0
[ 767.672625] show_stack+0x24/0x30
[ 767.675965] dump_stack_lvl+0x68/0x84
[ 767.679659] print_address_description.constprop.0+0x74/0x2b8
[ 767.685451] kasan_report+0x1f0/0x260
[ 767.689148] __asan_load2+0x94/0xd0
[ 767.692667] bond_3ad_state_machine_handler+0x13dc/0x1470