mac80211: always allocate struct ieee802_11_elems

As the 802.11 spec evolves, we need to parse more and more
elements. This is causing the struct to grow, and we can no
longer get away with putting it on the stack.

Change the API to always dynamically allocate and return an
allocated pointer that must be kfree()d later.

As an alternative, I contemplated a scheme whereby we'd say
in the code which elements we needed, e.g.

    DECLARE_ELEMENT_PARSER(elems,
                           SUPPORTED_CHANNELS,
                           CHANNEL_SWITCH,
                           EXT(KEY_DELIVERY));

    ieee802_11_parse_elems(..., &elems, ...);

and while I think this is possible and will save us a lot
since most individual places only care about a small subset
of the elements, it ended up being a bit more work since a
lot of places do the parsing and then pass the struct to
other functions, sometimes with multiple levels.

Link: https://lore.kernel.org/r/20210920154009.26caff6b5998.I05ae58768e990e611aee8eca8abefd9d7bc15e05@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 49 insertions, 36 deletions

diff --git a/net/mac80211/mesh.c b/net/mac80211/mesh.c
index 65e9335b3614..a4212a333d61 100644
--- a/net/mac80211/mesh.c
+++ b/net/mac80211/mesh.c
@@ -1246,7 +1246,7 @@ ieee80211_mesh_rx_probe_req(struct ieee80211_sub_if_data *sdata,
 	struct sk_buff *presp;
 	struct beacon_data *bcn;
 	struct ieee80211_mgmt *hdr;
-	struct ieee802_11_elems elems;
+	struct ieee802_11_elems *elems;
 	size_t baselen;
 	u8 *pos;
 
@@ -1255,22 +1255,24 @@ ieee80211_mesh_rx_probe_req(struct ieee80211_sub_if_data *sdata,
 	if (baselen > len)
 		return;
 
-	ieee802_11_parse_elems(pos, len - baselen, false, &elems, mgmt->bssid,
-			       NULL);
-
-	if (!elems.mesh_id)
+	elems = ieee802_11_parse_elems(pos, len - baselen, false, mgmt->bssid,
+				       NULL);
+	if (!elems)
 		return;
 
+	if (!elems->mesh_id)
+		goto free;
+
 	/* 802.11-2012 10.1.4.3.2 */
 	if ((!ether_addr_equal(mgmt->da, sdata->vif.addr) &&
 	     !is_broadcast_ether_addr(mgmt->da)) ||
-	    elems.ssid_len != 0)
-		return;
+	    elems->ssid_len != 0)
+		goto free;
 
-	if (elems.mesh_id_len != 0 &&
-	    (elems.mesh_id_len != ifmsh->mesh_id_len ||
-	     memcmp(elems.mesh_id, ifmsh->mesh_id, ifmsh->mesh_id_len)))
-		return;
+	if (elems->mesh_id_len != 0 &&
+	    (elems->mesh_id_len != ifmsh->mesh_id_len ||
+	     memcmp(elems->mesh_id, ifmsh->mesh_id, ifmsh->mesh_id_len)))
+		goto free;
 
 	rcu_read_lock();
 	bcn = rcu_dereference(ifmsh->beacon);
@@ -1294,6 +1296,8 @@ ieee80211_mesh_rx_probe_req(struct ieee80211_sub_if_data *sdata,
 	ieee80211_tx_skb(sdata, presp);
 out:
 	rcu_read_unlock();
+free:
+	kfree(elems);
 }
 
 static void ieee80211_mesh_rx_bcn_presp(struct ieee80211_sub_if_data *sdata,
@@ -1304,7 +1308,7 @@ static void ieee80211_mesh_rx_bcn_presp(struct ieee80211_sub_if_data *sdata,
 {
 	struct ieee80211_local *local = sdata->local;
 	struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
-	struct ieee802_11_elems elems;
+	struct ieee802_11_elems *elems;
 	struct ieee80211_channel *channel;
 	size_t baselen;
 	int freq;
@@ -1319,42 +1323,47 @@ static void ieee80211_mesh_rx_bcn_presp(struct ieee80211_sub_if_data *sdata,
 	if (baselen > len)
 		return;
 
-	ieee802_11_parse_elems(mgmt->u.probe_resp.variable, len - baselen,
-			       false, &elems, mgmt->bssid, NULL);
+	elems = ieee802_11_parse_elems(mgmt->u.probe_resp.variable,
+				       len - baselen,
+				       false, mgmt->bssid, NULL);
+	if (!elems)
+		return;
 
 	/* ignore non-mesh or secure / unsecure mismatch */
-	if ((!elems.mesh_id || !elems.mesh_config) ||
-	    (elems.rsn && sdata->u.mesh.security == IEEE80211_MESH_SEC_NONE) ||
-	    (!elems.rsn && sdata->u.mesh.security != IEEE80211_MESH_SEC_NONE))
-		return;
+	if ((!elems->mesh_id || !elems->mesh_config) ||
+	    (elems->rsn && sdata->u.mesh.security == IEEE80211_MESH_SEC_NONE) ||
+	    (!elems->rsn && sdata->u.mesh.security != IEEE80211_MESH_SEC_NONE))
+		goto free;
 
-	if (elems.ds_params)
-		freq = ieee80211_channel_to_frequency(elems.ds_params[0], band);
+	if (elems->ds_params)
+		freq = ieee80211_channel_to_frequency(elems->ds_params[0], band);
 	else
 		freq = rx_status->freq;
 
 	channel = ieee80211_get_channel(local->hw.wiphy, freq);
 
 	if (!channel || channel->flags & IEEE80211_CHAN_DISABLED)
-		return;
+		goto free;
 
-	if (mesh_matches_local(sdata, &elems)) {
+	if (mesh_matches_local(sdata, elems)) {
 		mpl_dbg(sdata, "rssi_threshold=%d,rx_status->signal=%d\n",
 			sdata->u.mesh.mshcfg.rssi_threshold, rx_status->signal);
 		if (!sdata->u.mesh.user_mpm ||
 		    sdata->u.mesh.mshcfg.rssi_threshold == 0 ||
 		    sdata->u.mesh.mshcfg.rssi_threshold < rx_status->signal)
-			mesh_neighbour_update(sdata, mgmt->sa, &elems,
+			mesh_neighbour_update(sdata, mgmt->sa, elems,
 					      rx_status);
 
 		if (ifmsh->csa_role != IEEE80211_MESH_CSA_ROLE_INIT &&
 		    !sdata->vif.csa_active)
-			ieee80211_mesh_process_chnswitch(sdata, &elems, true);
+			ieee80211_mesh_process_chnswitch(sdata, elems, true);
 	}
 
 	if (ifmsh->sync_ops)
 		ifmsh->sync_ops->rx_bcn_presp(sdata, stype, mgmt, len,
-					      elems.mesh_config, rx_status);
+					      elems->mesh_config, rx_status);
+free:
+	kfree(elems);
 }
 
 int ieee80211_mesh_finish_csa(struct ieee80211_sub_if_data *sdata)
@@ -1446,7 +1455,7 @@ static void mesh_rx_csa_frame(struct ieee80211_sub_if_data *sdata,
 			      struct ieee80211_mgmt *mgmt, size_t len)
 {
 	struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
-	struct ieee802_11_elems elems;
+	struct ieee802_11_elems *elems;
 	u16 pre_value;
 	bool fwd_csa = true;
 	size_t baselen;
@@ -1459,33 +1468,37 @@ static void mesh_rx_csa_frame(struct ieee80211_sub_if_data *sdata,
 	pos = mgmt->u.action.u.chan_switch.variable;
 	baselen = offsetof(struct ieee80211_mgmt,
 			   u.action.u.chan_switch.variable);
-	ieee802_11_parse_elems(pos, len - baselen, true, &elems,
-			       mgmt->bssid, NULL);
-
-	if (!mesh_matches_local(sdata, &elems))
+	elems = ieee802_11_parse_elems(pos, len - baselen, true,
+				       mgmt->bssid, NULL);
+	if (!elems)
 		return;
 
-	ifmsh->chsw_ttl = elems.mesh_chansw_params_ie->mesh_ttl;
+	if (!mesh_matches_local(sdata, elems))
+		goto free;
+
+	ifmsh->chsw_ttl = elems->mesh_chansw_params_ie->mesh_ttl;
 	if (!--ifmsh->chsw_ttl)
 		fwd_csa = false;
 
-	pre_value = le16_to_cpu(elems.mesh_chansw_params_ie->mesh_pre_value);
+	pre_value = le16_to_cpu(elems->mesh_chansw_params_ie->mesh_pre_value);
 	if (ifmsh->pre_value >= pre_value)
-		return;
+		goto free;
 
 	ifmsh->pre_value = pre_value;
 
 	if (!sdata->vif.csa_active &&
-	    !ieee80211_mesh_process_chnswitch(sdata, &elems, false)) {
+	    !ieee80211_mesh_process_chnswitch(sdata, elems, false)) {
 		mcsa_dbg(sdata, "Failed to process CSA action frame");
-		return;
+		goto free;
 	}
 
 	/* forward or re-broadcast the CSA frame */
 	if (fwd_csa) {
-		if (mesh_fwd_csa_frame(sdata, mgmt, len, &elems) < 0)
+		if (mesh_fwd_csa_frame(sdata, mgmt, len, elems) < 0)
 			mcsa_dbg(sdata, "Failed to forward the CSA frame");
 	}
+free:
+	kfree(elems);
 }
 
 static void ieee80211_mesh_rx_mgmt_action(struct ieee80211_sub_if_data *sdata,