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

[Wen Gong]

On 4/18/2023 5:11 PM, Johannes Berg wrote:
> 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

Hi Johannes, if you have any patch to fix it, I can download and test.