wifi: mac80211: mlme: re-parse if AP mode is less than client

If the AP mode ends up being determined less than the client mode,
there may be different reasons for this, e.g. AP misconfiguration.
If this happens in a way that causes e.g. EHT to be rejected, the
elements need to be re-parsed since we'll connect as HE, but not
reparsing means that we'll still think it's OK to use multi-link,
so we can connect in a non-sensical configuration of advertising
only HE on a secondary link. This normally won't happen for the
assoc link because that reuses the mode from authentication, and
if that's not EHT, multi-link association is rejected.

Fix this inconsistency by parsing the elements again if the mode
was different from the first parsing attempt. Print the message a
bit later to avoid printing "determined AP ... to be HE" twice in
cases where ieee80211_determine_ap_chan() returned a lesser mode,
rather than the regulatory downgrades below changing it.

Fixes: 310c8387c638 ("wifi: mac80211: clean up connection process")
Reviewed-by: Miriam Rachel Korenblit <[email protected]>
Link: https://msgid.link/20240418105220.d1f25d92cfe7.Ia21eff6cdcae2f5aca13cf8e742a986af5e70f89@changeid
Signed-off-by: Johannes Berg <[email protected]>

diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index 6fa3752b740ea195043073148a36190f398ddf58..502c34d52fbec78b1617aba6a1a086aabda0ed63 100644 (file)
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -632,15 +632,21 @@ again:
        ap_mode = ieee80211_determine_ap_chan(sdata, channel, bss->vht_cap_info,
                                              elems, false, conn, &ap_chandef);
 
-       mlme_link_id_dbg(sdata, link_id, "determined AP %pM to be %s\n",
-                        cbss->bssid, ieee80211_conn_mode_str(ap_mode));
-
        /* this should be impossible since parsing depends on our mode */
        if (WARN_ON(ap_mode > conn->mode)) {
                ret = -EINVAL;
                goto free;
        }
 
+       if (conn->mode != ap_mode) {
+               conn->mode = ap_mode;
+               kfree(elems);
+               goto again;
+       }
+
+       mlme_link_id_dbg(sdata, link_id, "determined AP %pM to be %s\n",
+                        cbss->bssid, ieee80211_conn_mode_str(ap_mode));
+
        sband = sdata->local->hw.wiphy->bands[channel->band];
 
        switch (channel->band) {
@@ -691,7 +697,6 @@ again:
                break;
        }
 
-       conn->mode = ap_mode;
        chanreq->oper = ap_chandef;
 
        /* wider-bandwidth OFDMA is only done in EHT */