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

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Date:   Fri, 7 Apr 2023 18:12:28 +0200
From:   Simon Horman <simon.horman@...igine.com>
To:     Jia-Ju Bai <baijiaju@...a.edu.cn>
Cc:     johannes@...solutions.net, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        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, Apr 04, 2023 at 08:47:34PM +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.
> 
> However, in the same call stack, sta->sdata is also used in the
> following functions:
> 
> ieee80211_ba_session_work()
>   ___ieee80211_stop_rx_ba_session(sta)
>     ht_dbg(sta->sdata, ...); -> No check
>     sdata_info(sta->sdata, ...); -> No check
>     ieee80211_send_delba(sta->sdata, ...) -> No check
>   ___ieee80211_start_rx_ba_session(sta)
>     ht_dbg(sta->sdata, ...); -> No check
>     ht_dbg_ratelimited(sta->sdata, ...); -> No check
>   ieee80211_tx_ba_session_handle_start(sta)
>     sdata = sta->sdata; if (!sdata) -> Add check by previous commit
>   ___ieee80211_stop_tx_ba_session(sdata)
>     ht_dbg(sta->sdata, ...); -> No check
>   ieee80211_start_tx_ba_cb(sdata)
>     sdata = sta->sdata; local = sdata->local -> No check
>   ieee80211_stop_tx_ba_cb(sdata)
>     ht_dbg(sta->sdata, ...); -> No check
> 
> Thus, to avoid possible null-pointer dereferences, the related checks
> should be added.
> 
> These bugs are reported by a static analysis tool implemented by myself,
> and they are found by extending a known bug fixed in the previous commit.
> Thus, they could be theoretical bugs.
> 
> Signed-off-by: Jia-Ju Bai <baijiaju@...a.edu.cn>

Reviewed-by: Simon Horman <simon.horman@...igine.com>