wifi: mac80211: start building elements in SKBs

The building of elements is really mess, and really the only
reason we're not doing it in SKBs in the first place is that
the scan code in ieee80211_build_preq_ies() doesn't.

Convert ieee80211_build_preq_ies() to use an SKB internally
so that we can gradually convert other things to ..._put_*()
style interfaces.

Link: https://msgid.link/20240129202041.c3a8e3c2cc99.I9d9920858c30ae5154719783933de0d7bc2a2cb9@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/ieee80211_i.h

@@ -2517,16 +2517,15 @@ void ieee80211_add_s1g_capab_ie(struct ieee80211_sub_if_data *sdata,
 				struct sk_buff *skb);
 void ieee80211_add_aid_request_ie(struct ieee80211_sub_if_data *sdata,
 				  struct sk_buff *skb);
-u8 *ieee80211_ie_build_s1g_cap(u8 *pos, struct ieee80211_sta_s1g_cap *s1g_cap);
 
 /* element building in SKBs */
 int ieee80211_put_srates_elem(struct sk_buff *skb,
 			      const struct ieee80211_supported_band *sband,
 			      u32 basic_rates, u32 rate_flags, u32 masked_rates,
 			      u8 element_id);
-void ieee80211_put_he_6ghz_cap(struct sk_buff *skb,
-			       struct ieee80211_sub_if_data *sdata,
-			       enum ieee80211_smps_mode smps_mode);
+int ieee80211_put_he_6ghz_cap(struct sk_buff *skb,
+			      struct ieee80211_sub_if_data *sdata,
+			      enum ieee80211_smps_mode smps_mode);
 
 /* channel management */
 bool ieee80211_chandef_ht_oper(const struct ieee80211_ht_operation *ht_oper,

net/mac80211/scan.c

@@ -400,6 +400,8 @@ static bool ieee80211_prep_hw_scan(struct ieee80211_sub_if_data *sdata)
 					 req->ie, req->ie_len,
 					 bands_used, req->rates, &chandef,
 					 flags);
+	if (ielen < 0)
+		return false;
 	local->hw_scan_req->req.ie_len = ielen;
 	local->hw_scan_req->req.no_cck = req->no_cck;
 	ether_addr_copy(local->hw_scan_req->req.mac_addr, req->mac_addr);
@@ -1322,19 +1324,21 @@ int __ieee80211_request_sched_scan_start(struct ieee80211_sub_if_data *sdata,
 
 	ieee80211_prepare_scan_chandef(&chandef);
 
-	ieee80211_build_preq_ies(sdata, ie, num_bands * iebufsz,
-				 &sched_scan_ies, req->ie,
-				 req->ie_len, bands_used, rate_masks, &chandef,
-				 flags);
+	ret = ieee80211_build_preq_ies(sdata, ie, num_bands * iebufsz,
+				       &sched_scan_ies, req->ie,
+				       req->ie_len, bands_used, rate_masks,
+				       &chandef, flags);
+	if (ret < 0)
+		goto error;
 
 	ret = drv_sched_scan_start(local, sdata, req, &sched_scan_ies);
 	if (ret == 0) {
 		rcu_assign_pointer(local->sched_scan_sdata, sdata);
 		rcu_assign_pointer(local->sched_scan_req, req);
 	}
 
+error:
 	kfree(ie);
-
 out:
 	if (ret) {
 		/* Clean in case of failure after HW restart or upon resume. */