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, 6 insertions, 5 deletions

diff --git a/net/mac80211/agg-rx.c b/net/mac80211/agg-rx.c
index cce28e3b2232..94c65def102c 100644
--- a/net/mac80211/agg-rx.c
+++ b/net/mac80211/agg-rx.c
@@ -477,7 +477,7 @@ void ieee80211_process_addba_request(struct ieee80211_local *local,
 				     size_t len)
 {
 	u16 capab, tid, timeout, ba_policy, buf_size, start_seq_num;
-	struct ieee802_11_elems elems = { };
+	struct ieee802_11_elems *elems = NULL;
 	u8 dialog_token;
 	int ies_len;
 
@@ -495,16 +495,17 @@ void ieee80211_process_addba_request(struct ieee80211_local *local,
 	ies_len = len - offsetof(struct ieee80211_mgmt,
 				 u.action.u.addba_req.variable);
 	if (ies_len) {
-		ieee802_11_parse_elems(mgmt->u.action.u.addba_req.variable,
-                                ies_len, true, &elems, mgmt->bssid, NULL);
-		if (elems.parse_error)
+		elems = ieee802_11_parse_elems(mgmt->u.action.u.addba_req.variable,
+					       ies_len, true, mgmt->bssid, NULL);
+		if (!elems || elems->parse_error)
 			return;
 	}
 
 	__ieee80211_start_rx_ba_session(sta, dialog_token, timeout,
 					start_seq_num, ba_policy, tid,
 					buf_size, true, false,
-					elems.addba_ext_ie);
+					elems ? elems->addba_ext_ie : NULL);
+	kfree(elems);
 }
 
 void ieee80211_manage_rx_ba_offl(struct ieee80211_vif *vif,