parsing the multi-link element with STA profile wifi: mac80211: support MLO authentication/association with one link

[Johannes Berg]

On Tue, 2023-04-18 at 17:02 +0800, Wen Gong wrote:
> On 4/18/2023 4:48 PM, Johannes Berg wrote:
> > Hi,
> > 
> > > My case is:
> > > When connect with 2 links AP, the cfg80211_hold_bss() is called by
> > > cfg80211_mlme_assoc()
> > > for each BSS of the 2 links,
> > > 
> > > When asssocResp from AP is not success(such as status_code==1), the
> > > ieee80211_link_data of 2nd link(sdata->link[link_id])
> > > is NULL because ieee80211_assoc_success()->ieee80211_vif_update_links()
> > > is not called.
> > > 
> > > Then struct cfg80211_rx_assoc_resp resp in cfg80211_rx_assoc_resp() and
> > > struct cfg80211_connect_resp_params cr in __cfg80211_connect_result()
> > > will only have the data of
> > > the 1st link, and finally cfg80211_connect_result_release_bsses() only
> > > call cfg80211_unhold_bss()
> > > for the 1st link, then BSS of the 2nd link will never free because its
> > > hold is awlays > 0 now.
> > Hah, yes, ouch.
> > 
> > > I found it is not easy to refine it, so do you have any advise/idea?
> > > 
> > > for (link_id = 0; link_id < IEEE80211_MLD_MAX_NUM_LINKS; link_id++) {
> > >           struct ieee80211_link_data *link;
> > > 
> > >           link = sdata_dereference(sdata->link[link_id], sdata);
> > >           if (!link)
> > >               continue;
> > > 
> > >           if (!assoc_data->link[link_id].bss)
> > >               continue;
> > > 
> > >           resp.links[link_id].bss = assoc_data->link[link_id].bss;
> > >           resp.links[link_id].addr = link->conf->addr;
> > >           resp.links[link_id].status = assoc_data->link[link_id].status;
> > > 
> > But is it really so hard? We only need link for link->conf->addr, and we
> > can use assoc_data->link[link_id].addr for that instead, no? We need to
> > store those locally to avoid a use-after-free, but that's at most 15
> > addresses on the stack, which seems acceptable?
> > 
> > Oh and there's the uapsd stuff but that only matters in the success case
> > anyway. In fact I'm not even sure the address matters in the
> > unsuccessful case but we have it pretty easily.
> > 
> > johannes
> OK. So I guess you already have good way to refine it?
> 

No, not really, was just thinking out loud here :)

johannes