linux-kernel - RE: [PATCH rtw v4 1/4] wifi: rtw89: fix use-after-free in rtw89_core_tx_kick_off_and

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Message-ID: <5d1be8c759c243f9a331c672cc301bbc@realtek.com>
Date: Thu, 18 Sep 2025 04:40:55 +0000
From: Zong-Zhe Yang <kevin_yang@...ltek.com>
To: Ping-Ke Shih <pkshih@...ltek.com>, Fedor Pchelkin <pchelkin@...ras.ru>
CC: Bitterblue Smith <rtl8821cerfe2@...il.com>,
        Bernie Huang
	<phhuang@...ltek.com>,
        "linux-wireless@...r.kernel.org"
	<linux-wireless@...r.kernel.org>,
        "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>,
        "lvc-project@...uxtesting.org"
	<lvc-project@...uxtesting.org>,
        "stable@...r.kernel.org"
	<stable@...r.kernel.org>
Subject: RE: [PATCH rtw v4 1/4] wifi: rtw89: fix use-after-free in rtw89_core_tx_kick_off_and_wait()

Ping-Ke Shih <pkshih@...ltek.com> wrote:
> 
> Fedor Pchelkin <pchelkin@...ras.ru> wrote:
> 
> [...]
> 
> > @@ -6181,6 +6187,27 @@ rtw89_assoc_link_rcu_dereference(struct rtw89_dev *rtwdev,
> u8 macid)
> >         list_first_entry_or_null(&p->dlink_pool,
> > typeof(*p->links_inst), dlink_schd); \
> >  })
> >
> > +static inline void rtw89_tx_wait_release(struct rtw89_tx_wait_info
> > +*wait) {
> > +       dev_kfree_skb_any(wait->skb);
> > +       kfree_rcu(wait, rcu_head);
> > +}
> > +
> > +static inline void rtw89_tx_wait_list_clear(struct rtw89_dev *rtwdev)
> > +{
> > +       struct rtw89_tx_wait_info *wait, *tmp;
> > +
> > +       lockdep_assert_wiphy(rtwdev->hw->wiphy);
> > +
> > +       list_for_each_entry_safe(wait, tmp, &rtwdev->tx_waits, list) {
> > +               if (!wait_for_completion_timeout(&wait->completion,
> > +
> RTW89_TX_WAIT_DEFAULT_TIMEOUT))
> > +                       continue;
> 
> 
> Why should we wait 10ms? Just try_wait_for_completion()?
> 
> Since TX completion might be missing (rtw89_core_stop(), for example), shouldn't we
> unconditionally free all in wait list for that case?
> 

In hci reset (when we release pending skb), the condition will become true.
So, all left will be freed at that time. Before that, there is no logic to ensure no
more completing side, so it cannot be unconditionally freed unless we don't
want to double check if those, which timed out, are done at some moment.

(e.g. core stop will do hci reset)

> 
> > +               list_del(&wait->list);
> > +               rtw89_tx_wait_release(wait);
> > +       }
> > +}
> > +
> >  static inline int rtw89_hci_tx_write(struct rtw89_dev *rtwdev,
> >                                      struct rtw89_core_tx_request *tx_req)
> >  {
>