RE: [PATCH] wifi: mac80211: fix NULL dereference at band check in starting tx ba session

[Zong-Zhe Yang <kevin_yang@realtek.com>]

Johannes Berg <johannes@sipsolutions.net> wrote:

> On Thu, 2024-05-30 at 13:49 +0000, Zong-Zhe Yang wrote:
> >
> > I think there are two points here.
> >
> > 1. the way to avoid this NULL dereference (Current patch just followed
> > original logic and made it runnable on both MLD and non-MLD.)
> >
> > According to comments, I will change to check
> ht_supported/vht_supported/has_he/has_eht.
> > Then, it doesn't need to reference chanreq.oper.chan here. So, there won't be NULL
> dereference.
> >
> > 2. the check logic when MLD
> > (Current patch didn't consider this properly.)
> >
> > According to spec., BA agreement does once per TID and apply to all corresponding links.
> > So, I am thinking maybe I check the conditions on all valid_links when MLD.
> > And, only check deflink when non-MLD.
> 
> Well, spec also requires that you have EHT (on all links) to be able to do MLO in the first place,
> so you shouldn't be connected. IOW, checking one link should be sufficient? And that can even
> be deflink, because for a STA that's always used as the assoc link (unlike for vif)
> 

Then I am thinking to just check ht_supported/vht_supported/has_he/has_eht on sta deflink,
whether non-MLD connection or MLD connection.
Any further suggestions?