linux-kernel - Re: [PATCH] cfg80211: free the object allocated in wiphy_apply_custom

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Date:   Fri, 23 Jul 2021 17:30:46 +0800
From:   Dongliang Mu <mudongliangabcd@...il.com>
To:     Johannes Berg <johannes@...solutions.net>
Cc:     Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Luca Coelho <luciano.coelho@...el.com>,
        Ilan Peer <ilan.peer@...el.com>,
        syzbot+1638e7c770eef6b6c0d0@...kaller.appspotmail.com,
        linux-wireless@...r.kernel.org,
        "open list:NETWORKING [GENERAL]" <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Dan Carpenter <dan.carpenter@...cle.com>
Subject: Re: [PATCH] cfg80211: free the object allocated in wiphy_apply_custom_regulatory

On Fri, Jul 23, 2021 at 5:18 PM Johannes Berg <johannes@...solutions.net> wrote:
>
> On Fri, 2021-07-23 at 17:13 +0800, Dongliang Mu wrote:
> > On Fri, Jul 23, 2021 at 4:37 PM Johannes Berg <johannes@...solutions.net> wrote:
> > >
> > > On Fri, 2021-07-23 at 13:09 +0800, Dongliang Mu wrote:
> > > > The commit beee24695157 ("cfg80211: Save the regulatory domain when
> > > > setting custom regulatory") forgets to free the newly allocated regd
> > > > object.
> > >
> > > Not really? It's not forgetting it, it just saves it?
> >
> > Yes, it saves the regd object in the function wiphy_apply_custom_regulatory.
>
> Right.
>
> > But its parent function - mac80211_hwsim_new_radio forgets to free
> > this object when the ieee80211_register_hw fails.
>
> But why is this specific to mac80211-hwsim?
>
> Any other code calling wiphy_apply_custom_regulatory() and then failing
> the subsequent wiphy_register() or otherwise calling wiphy_free() will
> run into the same situation.
>
> So why wouldn't we free this in wiphy_free(), if it exists?
>

Hi Johannes,

if zhao in the thread is right, we don't need to add this free
operation to wiphy_free().

What we should do is to only handle regd in the error handling code of
mac80211_hwsim_new_radio. This will not affect other users of
mac80211-hwsim. Any idea?

> johannes
>