[PATCH] brcmsmac: fix NULL pointer crash in brcms_c_regd_init()

["Arend van Spriel" <arend@broadcom.com>]

In the function brcms_c_regd_init() the channels are validated
against the device capabilities. This is done for both 2.4G and
5G band, but there are devices that are 2.4G only, ie. BCM4313.
For that device this leads to a NULL dereference. This patch adds
a check in brcms_c_regd_init() to fix this.

Issue introduced in wireless-next tree by following commit:
cf03c5d brcm80211: smac: inform mac80211 of the X2 regulatory domain

Cc: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
---
Noticed that one of smoketest machines actually was not sending results
ever since I staged regulatory fixes for it. This particular system has
a 2.4G card fitted so the root cause was quickly found.

Gr. AvS
---
 drivers/net/wireless/brcm80211/brcmsmac/channel.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/wireless/brcm80211/brcmsmac/channel.c b/drivers/net/wireless/brcm80211/brcmsmac/channel.c
index d3c7260..2d365d3 100644
--- a/drivers/net/wireless/brcm80211/brcmsmac/channel.c
+++ b/drivers/net/wireless/brcm80211/brcmsmac/channel.c
@@ -768,6 +768,11 @@ void brcms_c_regd_init(struct brcms_c_info *wlc)
 			band = wlc->bandstate[BAND_2G_INDEX];
 		else
 			band = wlc->bandstate[BAND_5G_INDEX];
+
+		/* skip if band not initialized */
+		if (band->pi == NULL)
+			continue;
+
 		wlc_phy_chanspec_band_validch(band->pi, band->bandtype,
 					      &sup_chan);
 
-- 
1.7.9.5