linux-kernel - Re: [PATCH] bluetooth/rfcomm: fix ODEBUG bug in rfcomm_dev

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Date:   Sun, 8 Mar 2020 16:27:02 +0800
From:   Qiujun Huang <hqjagain@...il.com>
To:     Marcel Holtmann <marcel@...tmann.org>
Cc:     Johan Hedberg <johan.hedberg@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Bluez mailing list <linux-bluetooth@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] bluetooth/rfcomm: fix ODEBUG bug in rfcomm_dev_ioctl

On Sun, Mar 8, 2020 at 4:18 PM Marcel Holtmann <marcel@...tmann.org> wrote:
>
> Hi Qiujun,
>
> > Needn't call 'rfcomm_dlc_put' here, because 'rfcomm_dlc_exists' didn't
> > increase dlc->refcnt.
> >
> > Reported-by: syzbot+4496e82090657320efc6@...kaller.appspotmail.com
> > Signed-off-by: Qiujun Huang <hqjagain@...il.com>
> > ---
> > net/bluetooth/rfcomm/tty.c | 1 -
> > 1 file changed, 1 deletion(-)
> >
> > diff --git a/net/bluetooth/rfcomm/tty.c b/net/bluetooth/rfcomm/tty.c
> > index 0c7d31c..ea2a1df0 100644
> > --- a/net/bluetooth/rfcomm/tty.c
> > +++ b/net/bluetooth/rfcomm/tty.c
> > @@ -414,7 +414,6 @@ static int __rfcomm_create_dev(struct sock *sk, void __user *arg)
> >               if (IS_ERR(dlc))
> >                       return PTR_ERR(dlc);
> >               else if (dlc) {
> > -                     rfcomm_dlc_put(dlc);
> >                       return -EBUSY;
> >               }
> >               dlc = rfcomm_dlc_alloc(GFP_KERNEL);
>
> Please see the proposed change from Hillf.
>
> It is better to not bother with the else if here since the if statement will already leave the function.

I get that. Thanks.

>
>         if (dlc)
>                 return -EBUSY;
>
> Regards
>
> Marcel
>