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

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Date:   Tue, 21 Mar 2023 09:36:23 +0100
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] net: mac80211: Add NULL checks for sta->sdata

On Tue, Mar 21, 2023 at 03:40:40PM +0800, Jia-Ju Bai wrote:
> Hello Simon,
> 
> Thanks for the reply!
> 
> 
> On 2023/3/21 0:49, Simon Horman wrote:
> > 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
> 
> Okay, I will revise it and run checkpatch.

Thanks.

> > > 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.
> 
> Okay, I will use this way in patch v2.

Maybe it is not a good idea.
But I think it is worth trying, at least locally, to see how it goes.

> > Also, are these theoretical bugs?
> > Or something that has been observed?
> > And has a reproducer?
> 
> These bugs are found by my static analysis tool, by extending a known bug
> fixed in a previous commit 69403bad97aa.
> Thus, they could be theoretical bugs.

Thanks, understood.
I think it would be worth making that a bit clearer in the
patch description (commit message).

> > > 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
> 
> I am quite sorry for this, because my script of git send email was buggy.
> I noticed this problem after sending the e-mail, and now I have fixed it :)

Thanks, I realised after I sent my previous email that something like that
might have happened. Thanks for fixing it.