linux-kernel - Re: [PATCH] mac80211: aggregation: Convert timers to use timer

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Message-ID: <1508359811.2674.56.camel@sipsolutions.net>
Date:   Wed, 18 Oct 2017 22:50:11 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     Kees Cook <keescook@...omium.org>
Cc:     linux-wireless <linux-wireless@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Network Development <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mac80211: aggregation: Convert timers to use
 timer_setup()

On Wed, 2017-10-18 at 07:19 -0700, Kees Cook wrote:
> On Wed, Oct 18, 2017 at 3:29 AM, Johannes Berg
> <johannes@...solutions.net> wrote:
> > > This has been the least trivial timer conversion yet. Given the use of
> > > RCU and other things I may not even know about, I'd love to get a close
> > > look at this. I *think* this is correct, as it will re-lookup the tid
> > > entries when firing the timer.
> > 
> > I'm not really sure why you're doing the lookup again? That seems
> > pointless, since you already have the right structure, and already rely
> > on it being valid. You can't really get a new struct assigned to the
> > same TID without the old one being destroyed.
> 
> I couldn't tell what the lifetime expectation was, so I left the
> re-lookup. I assumed it was possible to have a timer fire after the
> structure had been removed from the station structure.

Oh, right, I guess that would've been possible in theory. It's not
actually possible though since the aggregation sessions can't live on
without a station, so I've already made a follow-up patch to remove the
indirection.

johannes