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

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Date:   Mon, 20 Mar 2023 17:49:08 +0100
From:   Simon Horman <simon.horman@...igine.com>
To:     Jia-Ju Bai <baijiaju1990@...il.com>,
        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] net: mac80211: Add NULL checks for sta->sdata

On Mon, Mar 20, 2023 at 09:35:33PM +0800, Jia-Ju Bai wrote:
> In a previous commit 69403bad97aa, sta->sdata can be NULL, and thus it
> should be checked before being used.

Please run checkpatch on this patch, and correct the commit description
style.

./scripts/checkpatch.pl -g HEAD
ERROR: Please use git commit description style 'commit <12+ chars of sha1> ("<title line>")' - ie: 'commit 69403bad97aa ("wifi: mac80211: sdata can be NULL during AMPDU start")'
#6:
In a previous commit 69403bad97aa, sta->sdata can be NULL, and thus it

> 
> 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

I wonder if it would be better to teach ht_* do do nothing
if the first argument is NULL.

Also, are these theoretical bugs?
Or something that has been observed?
And has a reproducer?

> Thus, to avoid possible null-pointer dereferences, the related checks
> should be added.
> 
> These results are reported by a static tool designed by myself.
> 
> Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
> Reported-by: TOTE Robot <baijiaju@...a.edu.cn>

I see 4 copies of this patch in a few minutes.
As per the FAQ [1], please leave at least 24h between posts of a patch.

[1] https://www.kernel.org/doc/html/latest/process/maintainer-netdev.html