linux-kernel - Re: [PATCH] mac80211: fix race in ieee80211_register

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Date:   Mon, 06 Apr 2020 17:06:19 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     Krishna Chaitanya <chaitanya.mgit@...il.com>
Cc:     Kalle Valo <kvalo@...eaurora.org>,
        Sumit Garg <sumit.garg@...aro.org>,
        linux-wireless <linux-wireless@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>, kuba@...nel.org,
        netdev <netdev@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Matthias-Peter Schöpfer 
        <matthias.schoepfer@...inx.io>,
        "Berg Philipp (HAU-EDS)" <Philipp.Berg@...bherr.com>,
        "Weitner Michael (HAU-EDS)" <Michael.Weitner@...bherr.com>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Loic Poulain <loic.poulain@...aro.org>, stable@...r.kernel.org
Subject: Re: [PATCH] mac80211: fix race in ieee80211_register_hw()

On Mon, 2020-04-06 at 19:55 +0530, Krishna Chaitanya wrote:

> > iw phy0 interface add wlan0 type station
> > ip link set wlan0 up
> Ah okay, got it, thanks. Very narrow window though :-) as the
> alloc_ordered_workqueue
> doesn't need RTNL and there is a long way to go to do if_add() from
> user and setup
> the driver for interrupts. 

True, I do wonder how this is hit. Maybe something with no preempt and a
uevent triggering things?

> Again depends on the driver though, it
> should properly handle
> pending ieee80211_register_hw() with start().

It could, but it'd be really tricky. Much better to fix mac80211.

johannes