netdev - Re: [RESEND 1/1] Bluetooth: Use chan_list_lock to protect the whole put/destroy invokation

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Date:   Fri, 15 Jul 2022 08:28:37 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Luiz Augusto von Dentz <luiz.dentz@...il.com>
Cc:     Eric Dumazet <edumazet@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>, stable@...nel.org,
        Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "linux-bluetooth@...r.kernel.org" <linux-bluetooth@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>
Subject: Re: [RESEND 1/1] Bluetooth: Use chan_list_lock to protect the whole
 put/destroy invokation

> Hi Lee,
> > > > > > I'm struggling to apply this for test:
> > > > > >
> > > > > >   "error: corrupt patch at line 6"
> > > > >
> > > > > Check with the attached patch.
> > > >
> > > > With the patch applied:
> > > >
> > > > [  188.825418][   T75] refcount_t: addition on 0; use-after-free.
> > > > [  188.825418][   T75] refcount_t: addition on 0; use-after-free.
> > >
> > > Looks like the changes just make the issue more visible since we are
> > > trying to add a refcount when it is already 0 so this proves the
> > > design is not quite right since it is removing the object from the
> > > list only when destroying it while we probably need to do it before.
> > >
> > > How about we use kref_get_unless_zero as it appears it was introduced
> > > exactly for such cases (patch attached.)
> >
> > Looks like I missed a few places like l2cap_global_chan_by_psm so here
> > is another version.
> 
> Any feedback regarding these changes?

Not yet.  I'll have time to test this next week.

Things really stacked up this week, apologies.

-- 
Lee Jones [李琼斯]
Principal Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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