ath10k: fix scan crash due to incorrect length calculation

BugLink: https://bugs.launchpad.net/bugs/1801893

commit c8291988 upstream.

Length of WMI scan message was not calculated correctly. The allocated
buffer was smaller than what we expected. So WMI message corrupted
skb_info, which is at the end of skb->data. This fix takes TLV header
into account even if the element is zero-length.

Crash log:
  [49.629986] Unhandled kernel unaligned access[#1]:
  [49.634932] CPU: 0 PID: 1176 Comm: logd Not tainted 4.4.60 #180
  [49.641040] task: 83051460 ti: 8329c000 task.ti: 8329c000
  [49.646608] $ 0   : 00000000 00000001 80984a80 00000000
  [49.652038] $ 4   : 45259e89 8046d484 8046df30 8024ba70
  [49.657468] $ 8   : 00000000 804cc4c0 00000001 20306320
  [49.662898] $12   : 33322037 000110f2 00000000 31203930
  [49.668327] $16   : 82792b40 80984a80 00000001 804207fc
  [49.673757] $20   : 00000000 0000012c 00000040 80470000
  [49.679186] $24   : 00000000 8024af7c
  [49.684617] $28   : 8329c000 8329db88 00000001 802c58d0
  [49.690046] Hi    : 00000000
  [49.693022] Lo    : 453c0000
  [49.696013] epc   : 800efae4 put_page+0x0/0x58
  [49.700615] ra    : 802c58d0 skb_release_data+0x148/0x1d4
  [49.706184] Status: 1000fc03 KERNEL EXL IE
  [49.710531] Cause : 00800010 (ExcCode 04)
  [49.714669] BadVA : 45259e89
  [49.717644] PrId  : 00019374 (MIPS 24Kc)
Signed-off-by: Zhi Chen <zhichen@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Cc: Brian Norris <briannorris@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

drivers/net/wireless/ath/ath10k/wmi-tlv.c

@@ -1459,10 +1459,10 @@ ath10k_wmi_tlv_op_gen_start_scan(struct ath10k *ar,
 	bssid_len = arg->n_bssids * sizeof(struct wmi_mac_addr);
 	ie_len = roundup(arg->ie_len, 4);
 	len = (sizeof(*tlv) + sizeof(*cmd)) +
-	      (arg->n_channels ? sizeof(*tlv) + chan_len : 0) +
-	      (arg->n_ssids ? sizeof(*tlv) + ssid_len : 0) +
-	      (arg->n_bssids ? sizeof(*tlv) + bssid_len : 0) +
-	      (arg->ie_len ? sizeof(*tlv) + ie_len : 0);
+	      sizeof(*tlv) + chan_len +
+	      sizeof(*tlv) + ssid_len +
+	      sizeof(*tlv) + bssid_len +
+	      sizeof(*tlv) + ie_len;
 
 	skb = ath10k_wmi_alloc_skb(ar, len);
 	if (!skb)