linux-kernel - Re: [PATCH] usb: gadget: u_serial: Add null pointer check in gserial

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Message-ID: <16b5ad34bc3791223a2754cec8557fa5bd24c314.camel@mediatek.com>
Date:   Thu, 25 May 2023 07:00:22 +0000
From:   Chunfeng Yun (云春峰) 
        <Chunfeng.Yun@...iatek.com>
To:     "quic_prashk@...cinc.com" <quic_prashk@...cinc.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "fabrice.gasnier@...com" <fabrice.gasnier@...com>,
        "stable@...nel.org" <stable@...nel.org>,
        "balbi@...nel.org" <balbi@...nel.org>,
        "xiujianfeng@...wei.com" <xiujianfeng@...wei.com>,
        Kewu Chen (陈科伍) <Kewu.Chen@...iatek.com>,
        "stern@...land.harvard.edu" <stern@...land.harvard.edu>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "christophe.jaillet@...adoo.fr" <christophe.jaillet@...adoo.fr>,
        "angelogioacchino.delregno@...labora.com" 
        <angelogioacchino.delregno@...labora.com>
Subject: Re: [PATCH] usb: gadget: u_serial: Add null pointer check in
 gserial_suspend

On Mon, 2023-05-22 at 11:19 +0530, Prashanth K wrote:
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
> 
> 
> On 22-05-23 07:51 am, Chunfeng Yun wrote:
> > When gserial_disconnect has already cleared gser->ioport, and the
> > suspend triggers afterwards, gserial_suspend gets called, which
> > will
> > lead to accessing of gser->ioport and thus causing null pointer
> > dereference. Add a null pointer check to prevent it as the bellow
> > patch does:
> > 5ec63fdbca60 ("usb: gadget: u_serial: Add null pointer check in
> > gserial_resume")
> > 
> > Fixes: aba3a8d01d62 ("usb: gadget: u_serial: add suspend resume
> > callbacks")
> > Cc: stable <stable@...nel.org>
> > Signed-off-by: Chunfeng Yun <chunfeng.yun@...iatek.com>
> > ---
> >   drivers/usb/gadget/function/u_serial.c | 12 ++++++++++--
> >   1 file changed, 10 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/usb/gadget/function/u_serial.c
> > b/drivers/usb/gadget/function/u_serial.c
> > index a0ca47fbff0f..40ba220cf6d2 100644
> > --- a/drivers/usb/gadget/function/u_serial.c
> > +++ b/drivers/usb/gadget/function/u_serial.c
> > @@ -1420,10 +1420,18 @@ EXPORT_SYMBOL_GPL(gserial_disconnect);
> > 
> >   void gserial_suspend(struct gserial *gser)
> >   {
> > -     struct gs_port  *port = gser->ioport;
> > +     struct gs_port  *port;
> >       unsigned long   flags;
> > 
> > -     spin_lock_irqsave(&port->port_lock, flags);
> > +     spin_lock_irqsave(&serial_port_lock, flags);
> > +     port = gser->ioport;
> > +     if (!port) {
> > +             spin_unlock_irqrestore(&serial_port_lock, flags);
> > +             return;
> > +     }
> > +
> > +     spin_lock(&port->port_lock);
> > +     spin_unlock(&serial_port_lock);
> >       port->suspended = true;
> >       spin_unlock_irqrestore(&port->port_lock, flags);
> >   }
> 
> Hi Chunfeng,
> 
> This looks same as the following patch.
> 
https://lore.kernel.org/linux-usb/1683278317-11774-1-git-send-email-quic_prashk@quicinc.com/

Yes, it is, please ignore this one, thanks a lot

> 
> 
> Regards