mac80211: mesh: fix premature update of rc stats

mac80211: mesh: fix premature update of rc stats

The mesh_neighbour_update() function, queued via beacon rx, can race with
userspace creating the same station.  If the station already exists by the
time mesh_neighbour_update() is called, the function wrongly assumes rate
control has been initialized and calls rate_control_rate_update(), which
in turn calls into the driver.

Updating the rate control before it has been initialized can cause a
crash in some drivers, for example this firmware crash in ath10k due
to sta->rx_nss being 0:

[ 3078.088247] mesh0: Inserted STA 5c:e2:8c:f1:ab:ba
[ 3078.258407] ath10k_pci 0000:0d:00.0: firmware crashed! (uuid d6ed5961-93cc-4d61-803f-5eda55bb8643)
[ 3078.258421] ath10k_pci 0000:0d:00.0: qca988x hw2.0 target 0x4100016c chip_id 0x043202ff sub 0000:0000
[ 3078.258426] ath10k_pci 0000:0d:00.0: kconfig debug 1 debugfs 1 tracing 1 dfs 0 testmode 0
[ 3078.258608] ath10k_pci 0000:0d:00.0: firmware ver 10.2.4.70.59-2 api 5 features no-p2p,raw-mode,mfp crc32 4159f498
[ 3078.258613] ath10k_pci 0000:0d:00.0: board_file api 1 bmi_id N/A crc32 bebc7c08
[ 3078.258617] ath10k_pci 0000:0d:00.0: htt-ver 2.1 wmi-op 5 htt-op 2 cal otp max-sta 128 raw 0 hwcrypto 1
[ 3078.260627] ath10k_pci 0000:0d:00.0: firmware register dump:
[ 3078.260640] ath10k_pci 0000:0d:00.0: [00]: 0x4100016C 0x000015B3 0x009A31BB 0x00955B31
[ 3078.260647] ath10k_pci 0000:0d:00.0: [04]: 0x009A31BB 0x00060130 0x00000008 0x00000007
[ 3078.260652] ath10k_pci 0000:0d:00.0: [08]: 0x00000000 0x00955B31 0x00000000 0x0040F89E
[ 3078.260656] ath10k_pci 0000:0d:00.0: [12]: 0x00000009 0xFFFFFFFF 0x009580F5 0x00958117
[ 3078.260660] ath10k_pci 0000:0d:00.0: [16]: 0x00958080 0x0094085D 0x00000000 0x00000000
[ 3078.260664] ath10k_pci 0000:0d:00.0: [20]: 0x409A31BB 0x0040AA84 0x00000002 0x00000001
[ 3078.260669] ath10k_pci 0000:0d:00.0: [24]: 0x809A2B8D 0x0040AAE4 0x00000088 0xC09A31BB
[ 3078.260673] ath10k_pci 0000:0d:00.0: [28]: 0x809898C8 0x0040AB04 0x0043F91C 0x009C6458
[ 3078.260677] ath10k_pci 0000:0d:00.0: [32]: 0x809B66AC 0x0040AB34 0x009C6458 0x0043F91C
[ 3078.260686] ath10k_pci 0000:0d:00.0: [36]: 0x809B2824 0x0040ADA4 0x00400000 0x00416EB4
[ 3078.260692] ath10k_pci 0000:0d:00.0: [40]: 0x809C07D9 0x0040ADE4 0x0040AE08 0x00412028
[ 3078.260696] ath10k_pci 0000:0d:00.0: [44]: 0x809486FA 0x0040AE04 0x00000001 0x00000000
[ 3078.260700] ath10k_pci 0000:0d:00.0: [48]: 0x80948E2C 0x0040AEA4 0x0041F4F0 0x00412634
[ 3078.260704] ath10k_pci 0000:0d:00.0: [52]: 0x809BFC39 0x0040AEC4 0x0041F4F0 0x00000001
[ 3078.260709] ath10k_pci 0000:0d:00.0: [56]: 0x80940F18 0x0040AF14 0x00000010 0x00403AC0
[ 3078.284130] ath10k_pci 0000:0d:00.0: failed to to request monitor vdev 1 stop: -108

Fix this by checking whether the sta has already initialized rate control
using the flag for that purpose.  We can also drop the unnecessary insert
parameter here.

Signed-off-by: Bob Copeland <bobcopeland@fb.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>