linux-kernel - Re: [PATCH v3] net: mac80211: Add NULL checks for sta->sdata

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Message-ID: <0e155b9612bef2c102a4ef5002c25a7ce5a2435e.camel@sipsolutions.net>
Date:   Tue, 11 Apr 2023 12:35:16 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     Jia-Ju Bai <baijiaju@...a.edu.cn>, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        simon.horman@...igine.com
Cc:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] net: mac80211: Add NULL checks for sta->sdata

On Tue, 2023-04-04 at 20:47 +0800, Jia-Ju Bai wrote:
> In a previous commit 69403bad97aa ("wifi: mac80211: sdata can be NULL
> during AMPDU start"), sta->sdata can be NULL, and thus it should be
> checked before being used.

Right.

> However, in the same call stack, sta->sdata is also used in the
> following functions:
> 

Fun, guess we should fix that too then.

Honestly though, I don't think this patch is the right way of going
about it. It seems that instead we should expand the checks in the
previous patch - see how it's talking about a race, and we don't really
want or need to handle aggregation for a station that's being removed.

So I think the better way to fix it would be to prevent the race more
clearly, though off the top of my head I'm not sure how we'd do that.

johannes