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, 24 insertions, 20 deletions

diff --git a/net/mac80211/mesh_hwmp.c b/net/mac80211/mesh_hwmp.c
index a05b615deb51..44a6fdb6efbd 100644
--- a/net/mac80211/mesh_hwmp.c
+++ b/net/mac80211/mesh_hwmp.c
@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Copyright (c) 2008, 2009 open80211s Ltd.
- * Copyright (C) 2019 Intel Corporation
+ * Copyright (C) 2019, 2021 Intel Corporation
  * Author:     Luis Carlos Cobo <luisca@cozybit.com>
  */
 
@@ -908,7 +908,7 @@ static void hwmp_rann_frame_process(struct ieee80211_sub_if_data *sdata,
 void mesh_rx_path_sel_frame(struct ieee80211_sub_if_data *sdata,
 			    struct ieee80211_mgmt *mgmt, size_t len)
 {
-	struct ieee802_11_elems elems;
+	struct ieee802_11_elems *elems;
 	size_t baselen;
 	u32 path_metric;
 	struct sta_info *sta;
@@ -926,37 +926,41 @@ void mesh_rx_path_sel_frame(struct ieee80211_sub_if_data *sdata,
 	rcu_read_unlock();
 
 	baselen = (u8 *) mgmt->u.action.u.mesh_action.variable - (u8 *) mgmt;
-	ieee802_11_parse_elems(mgmt->u.action.u.mesh_action.variable,
-			       len - baselen, false, &elems, mgmt->bssid, NULL);
+	elems = ieee802_11_parse_elems(mgmt->u.action.u.mesh_action.variable,
+				       len - baselen, false, mgmt->bssid, NULL);
+	if (!elems)
+		return;
 
-	if (elems.preq) {
-		if (elems.preq_len != 37)
+	if (elems->preq) {
+		if (elems->preq_len != 37)
 			/* Right now we support just 1 destination and no AE */
-			return;
-		path_metric = hwmp_route_info_get(sdata, mgmt, elems.preq,
+			goto free;
+		path_metric = hwmp_route_info_get(sdata, mgmt, elems->preq,
 						  MPATH_PREQ);
 		if (path_metric)
-			hwmp_preq_frame_process(sdata, mgmt, elems.preq,
+			hwmp_preq_frame_process(sdata, mgmt, elems->preq,
 						path_metric);
 	}
-	if (elems.prep) {
-		if (elems.prep_len != 31)
+	if (elems->prep) {
+		if (elems->prep_len != 31)
 			/* Right now we support no AE */
-			return;
-		path_metric = hwmp_route_info_get(sdata, mgmt, elems.prep,
+			goto free;
+		path_metric = hwmp_route_info_get(sdata, mgmt, elems->prep,
 						  MPATH_PREP);
 		if (path_metric)
-			hwmp_prep_frame_process(sdata, mgmt, elems.prep,
+			hwmp_prep_frame_process(sdata, mgmt, elems->prep,
 						path_metric);
 	}
-	if (elems.perr) {
-		if (elems.perr_len != 15)
+	if (elems->perr) {
+		if (elems->perr_len != 15)
 			/* Right now we support only one destination per PERR */
-			return;
-		hwmp_perr_frame_process(sdata, mgmt, elems.perr);
+			goto free;
+		hwmp_perr_frame_process(sdata, mgmt, elems->perr);
 	}
-	if (elems.rann)
-		hwmp_rann_frame_process(sdata, mgmt, elems.rann);
+	if (elems->rann)
+		hwmp_rann_frame_process(sdata, mgmt, elems->rann);
+free:
+	kfree(elems);
 }
 
 /**