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Date:   Wed, 15 Jun 2022 11:16:30 +0200
Message-ID: <87sfo64781.wl-tiwai@suse.de>
From:   Takashi Iwai <tiwai@suse.de>
To:     Toke =?ISO-8859-1?Q?H=F8iland-J=F8rgensen?= <toke@toke.dk>
Cc:     Kalle Valo <kvalo@kernel.org>,
        Pavel Skripkin <paskripkin@gmail.com>, davem@davemloft.net,
        kuba@kernel.org, linux-wireless@vger.kernel.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        syzbot+03110230a11411024147@syzkaller.appspotmail.com,
        syzbot+c6dde1f690b60e0b9fbe@syzkaller.appspotmail.com
Subject: Re: [PATCH v6 1/2] ath9k: fix use-after-free in ath9k_hif_usb_rx_cb
In-Reply-To: <87tu8mxpnz.fsf@toke.dk>
References: <d57bbedc857950659bfacac0ab48790c1eda00c8.1655145743.git.paskripkin@gmail.com>
        <87o7yvzf33.fsf@toke.dk>
        <87k09ipfl9.fsf@kernel.org>
        <87tu8mxpnz.fsf@toke.dk>
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On Wed, 15 Jun 2022 11:05:20 +0200,
Toke H?iland-J?rgensen wrote:
> 
> Kalle Valo <kvalo@kernel.org> writes:
> 
> > Toke H?iland-J?rgensen <toke@toke.dk> writes:
> >
> >> Pavel Skripkin <paskripkin@gmail.com> writes:
> >>
> >>> Syzbot reported use-after-free Read in ath9k_hif_usb_rx_cb() [0]. The
> >>> problem was in incorrect htc_handle->drv_priv initialization.
> >>>
> >>> Probable call trace which can trigger use-after-free:
> >>>
> >>> ath9k_htc_probe_device()
> >>>   /* htc_handle->drv_priv = priv; */
> >>>   ath9k_htc_wait_for_target()      <--- Failed
> >>>   ieee80211_free_hw()		   <--- priv pointer is freed
> >>>
> >>> <IRQ>
> >>> ...
> >>> ath9k_hif_usb_rx_cb()
> >>>   ath9k_hif_usb_rx_stream()
> >>>    RX_STAT_INC()		<--- htc_handle->drv_priv access
> >>>
> >>> In order to not add fancy protection for drv_priv we can move
> >>> htc_handle->drv_priv initialization at the end of the
> >>> ath9k_htc_probe_device() and add helper macro to make
> >>> all *_STAT_* macros NULL safe, since syzbot has reported related NULL
> >>> deref in that macros [1]
> >>>
> >>> Link: https://syzkaller.appspot.com/bug?id=6ead44e37afb6866ac0c7dd121b4ce07cb665f60 [0]
> >>> Link: https://syzkaller.appspot.com/bug?id=b8101ffcec107c0567a0cd8acbbacec91e9ee8de [1]
> >>> Fixes: fb9987d0f748 ("ath9k_htc: Support for AR9271 chipset.")
> >>> Reported-and-tested-by: syzbot+03110230a11411024147@syzkaller.appspotmail.com
> >>> Reported-and-tested-by: syzbot+c6dde1f690b60e0b9fbe@syzkaller.appspotmail.com
> >>> Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
> >>
> >> Alright, since we've heard no more objections and the status quo is
> >> definitely broken, let's get this merged and we can follow up with any
> >> other fixes as necessary...
> >>
> >> Acked-by: Toke H?iland-J?rgensen <toke@toke.dk>
> >
> > I'm wondering should these go to -rc or -next? Has anyone actually
> > tested these with real hardware? (syzbot testing does not count) With
> > the past bad experience with syzbot fixes I'm leaning towards -next to
> > have more time to fix any regressions.
> 
> Hmm, good question. From Takashi's comment on v5, it seems like distros
> are going to backport it anyway, so in that sense it probably doesn't
> matter that much?

Well, it does matter if it really breaks things, of course ;)

> In any case I think it has a fairly low probability of breaking real
> users' setup (how often is that error path on setup even hit?), but I'm
> OK with it going to -next to be doubleplus-sure :)

Queuing to for-next is fine for us.  Backporting immediately or not
will be a decision by each distro, then. 

OTOH, if anyone has tested it beforehand on a real hardware and
confirmed, at least, that it works for normal cases (no error path),
that should suffice for -rc inclusion, too, IMO.


thanks,

Takashi