netdev - Re: [PATCH] mac80211: fix race in ieee80211_register

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Date:   Mon, 06 Apr 2020 14:47:43 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     Kalle Valo <kvalo@...eaurora.org>,
        Sumit Garg <sumit.garg@...aro.org>
Cc:     linux-wireless@...r.kernel.org, davem@...emloft.net,
        kuba@...nel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, matthias.schoepfer@...inx.io,
        Philipp.Berg@...bherr.com, Michael.Weitner@...bherr.com,
        daniel.thompson@...aro.org, loic.poulain@...aro.org,
        stable@...r.kernel.org
Subject: Re: [PATCH] mac80211: fix race in ieee80211_register_hw()

On Mon, 2020-04-06 at 15:44 +0300, Kalle Valo wrote:
> 
> >     user-space  ieee80211_register_hw()  RX IRQ
> >     +++++++++++++++++++++++++++++++++++++++++++++
> >        |                    |             |
> >        |<---wlan0---wiphy_register()      |
> >        |----start wlan0---->|             |
> >        |                    |<---IRQ---(RX packet)
> >        |              Kernel crash        |
> >        |              due to unallocated  |
> >        |              workqueue.          |

[snip]

> I have understood that no frames should be received until mac80211 calls
> struct ieee80211_ops::start:
> 
>  * @start: Called before the first netdevice attached to the hardware
>  *         is enabled. This should turn on the hardware and must turn on
>  *         frame reception (for possibly enabled monitor interfaces.)

True, but I think he's saying that you can actually add and configure an
interface as soon as the wiphy is registered?

The "wlan0" is kinda wrong there, should be "phy0" I guess, and then
interface added from iw?

johannes