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From:   Zheng Hacker <hackerzheng666@gmail.com>
Date:   Sat, 11 Mar 2023 00:51:07 +0800
Message-ID: <CAJedcCwFE0xsQpUYNS98J7WJxMrD9At8o2Km3AZo8CuNOvqJuw@mail.gmail.com>
Subject: Re: [PATCH net] xirc2ps_cs: Fix use after free bug in xirc2ps_detach
To:     Simon Horman <simon.horman@corigine.com>
Cc:     Zheng Wang <zyytlz.wz@163.com>, davem@davemloft.net,
        edumazet@google.com, kuba@kernel.org, pabeni@redhat.com,
        petrm@nvidia.com, thomas.lendacky@amd.com,
        wsa+renesas@sang-engineering.com, leon@kernel.org,
        shayagr@amazon.com, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, 1395428693sheep@gmail.com,
        alex000young@gmail.com
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Simon Horman <simon.horman@corigine.com> =E4=BA=8E2023=E5=B9=B43=E6=9C=8810=
=E6=97=A5=E5=91=A8=E4=BA=94 21:59=E5=86=99=E9=81=93=EF=BC=9A
>
> On Fri, Mar 10, 2023 at 12:57:29AM +0800, Zheng Wang wrote:
> > In xirc2ps_probe, the local->tx_timeout_task was bounded
> > with xirc2ps_tx_timeout_task. When timeout occurs,
> > it will call xirc_tx_timeout->schedule_work to start the
> > work.
> >
> > When we call xirc2ps_detach to remove the driver, there
> > may be a sequence as follows:
> >
> > Fix it by finishing the work before cleanup in xirc2ps_detach
> >
> > CPU0                  CPU1
> >
> >                     |xirc2ps_tx_timeout_task
> > xirc2ps_detach      |
> >   free_netdev       |
> >     kfree(dev);     |
> >                     |
> >                     | do_reset
> >                     |   //use
> >
> > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> > Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
> > ---
> >  drivers/net/ethernet/xircom/xirc2ps_cs.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/ethernet/xircom/xirc2ps_cs.c b/drivers/net/eth=
ernet/xircom/xirc2ps_cs.c
> > index 894e92ef415b..ea7b06f75691 100644
> > --- a/drivers/net/ethernet/xircom/xirc2ps_cs.c
> > +++ b/drivers/net/ethernet/xircom/xirc2ps_cs.c
> > @@ -503,7 +503,10 @@ static void
> >  xirc2ps_detach(struct pcmcia_device *link)
> >  {
> >      struct net_device *dev =3D link->priv;
> > -
> > +             struct local_info *local;
> > +
> > +             local =3D netdev_priv(dev);
> > +             cancel_work_sync(&local->tx_timeout_task)
> >      dev_dbg(&link->dev, "detach\n");
> >
> >      unregister_netdev(dev);
>
> This doesn't compile.
> Also, the indentation is incorrect.

Sorry for my mistake. I was hurried to report the issue and ignored
the compile test.

>
> I think what should have been posted is:

Yes, will correct it in the next version of patch.

Best regards,
Zheng

>
> diff --git a/drivers/net/ethernet/xircom/xirc2ps_cs.c b/drivers/net/ether=
net/xircom/xirc2ps_cs.c
> index 894e92ef415b..b607fea486ab 100644
> --- a/drivers/net/ethernet/xircom/xirc2ps_cs.c
> +++ b/drivers/net/ethernet/xircom/xirc2ps_cs.c
> @@ -503,7 +503,10 @@ static void
>  xirc2ps_detach(struct pcmcia_device *link)
>  {
>      struct net_device *dev =3D link->priv;
> +    struct local_info *local;
>
> +    local =3D netdev_priv(dev);
> +    cancel_work_sync(&local->tx_timeout_task);
>      dev_dbg(&link->dev, "detach\n");
>
>      unregister_netdev(dev);