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Subject: Re: [PATCH v3] net: mac80211: Add NULL checks for sta->sdata
From:   Johannes Berg <johannes@sipsolutions.net>
To:     Jia-Ju Bai <baijiaju@buaa.edu.cn>, davem@davemloft.net,
        edumazet@google.com, kuba@kernel.org, pabeni@redhat.com,
        simon.horman@corigine.com
Cc:     linux-wireless@vger.kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Date:   Tue, 11 Apr 2023 12:35:16 +0200
In-Reply-To: <20230404124734.201011-1-baijiaju@buaa.edu.cn>
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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:
>=20

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