netdev - Re: [PATCH v3 0/8] rtw88: prepare locking for SDIO support

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Date:   Sun, 30 Jan 2022 22:40:06 +0100
From:   Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To:     Pkshih <pkshih@...ltek.com>
Cc:     "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        "tony0620emma@...il.com" <tony0620emma@...il.com>,
        "kvalo@...eaurora.org" <kvalo@...eaurora.org>,
        "johannes@...solutions.net" <johannes@...solutions.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Neo Jou <neojou@...il.com>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Ed Swierk <eswierk@...st>
Subject: Re: [PATCH v3 0/8] rtw88: prepare locking for SDIO support

Hi Ping-Ke,

On Fri, Jan 28, 2022 at 1:51 AM Pkshih <pkshih@...ltek.com> wrote:
[...]
>
> > >
> > > To avoid this, we can add a flag to struct rtw_vif, and set this flag
> > > when ::remove_interface. Then, only collect vif without this flag into list
> > > when we use iterate_actiom().
> > >
> > > As well as ieee80211_sta can do similar fix.
> > >
>
> I would prefer my method that adds a 'bool disabled' flag to struct rtw_vif/rtw_sta
> and set it when ::remove_interface/::sta_remove. Then rtw_iterate_stas() can
> check this flag to decide whether does thing or not.
That would indeed be a very straight forward approach and easy to read.
In net/mac80211/iface.c there's some cases where after
drv_remove_interface() (which internally calls our .remove_interface
op) will kfree the vif (sdata). Doesn't that then result in a
use-after-free if we rely on a boolean within rtw_vif?

[...]
> > For the interface use-case it's not clear to me how this works at all.
> > rtw_ops_add_interface() has (in a simplified view):
> >     u8 port = 0;
> >     // the port variable is never changed
> >     rtwvif->port = port;
> >     rtwvif->conf = &rtw_vif_port[port];
> >     rtw_info(rtwdev, "start vif %pM on port %d\n", vif->addr, rtwvif->port);
> > How do multiple interfaces (vifs) work in rtw88 if the port is always
> > zero? Is some kind of tracking of the used ports missing (similar to
> > how we track the used station IDs - also called mac_id - in
> > rtw_dev->mac_id_map)?
>
> The port should be allocated dynamically if we support two or more vifs.
> We have internal tree that is going to support p2p by second vif.
I see, thanks for clarifying this!


Best regards,
Martin