mac80211: disable powersave for broken APs

Only AID values 1-2007 are valid, but some APs have been
found to send random bogus values, in the reported case an
AP that was sending the AID field value 0xffff, an AID of
0x3fff (16383).

There isn't much we can do but disable powersave since
there's no way it can work properly in this case.

Cc: [e-mail]
Reported-by: Bill C Riemers <[e-mail]>
Signed-off-by: Johannes Berg <[e-mail]>
Signed-off-by: John W. Linville <[e-mail]>

net/mac80211/ieee80211_i.h

···
 
 	unsigned long timers_running; /* used for quiesce/restart */
 	bool powersave; /* powersave requested for this iface */
+	bool broken_ap; /* AP is broken -- turn off powersave */
 	enum ieee80211_smps_mode req_smps, /* requested smps mode */
 				 ap_smps, /* smps mode AP thinks we're in */
 				 driver_smps_mode; /* smps mode request */

net/mac80211/mlme.c

···
 	if (!mgd->powersave)
 		return false;
 
+	if (mgd->broken_ap)
+		return false;
+
 	if (!mgd->associated)
 		return false;
 
···
 	capab_info = le16_to_cpu(mgmt->u.assoc_resp.capab_info);
 
 	if ((aid & (BIT(15) | BIT(14))) != (BIT(15) | BIT(14)))
-		printk(KERN_DEBUG "%s: invalid aid value %d; bits 15:14 not "
-		       "set\n", sdata->name, aid);
+		printk(KERN_DEBUG
+		       "%s: invalid AID value 0x%x; bits 15:14 not set\n",
+		       sdata->name, aid);
 	aid &= ~(BIT(15) | BIT(14));
+
+	ifmgd->broken_ap = false;
+
+	if (aid == 0 || aid > IEEE80211_MAX_AID) {
+		printk(KERN_DEBUG
+		       "%s: invalid AID value %d (out of range), turn off PS\n",
+		       sdata->name, aid);
+		aid = 0;
+		ifmgd->broken_ap = true;
+	}
 
 	pos = mgmt->u.assoc_resp.variable;
 	ieee802_11_parse_elems(pos, len - (pos - (u8 *) mgmt), &elems);