linux-kernel - Re: [PATCH] staging: rtl8712: Fix memory leak in r8712_init_recv

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Date:   Fri, 21 May 2021 15:16:07 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     慕冬亮 <mudongliangabcd@...il.com>
Cc:     Larry.Finger@...inger.net, florian.c.schilhabel@...glemail.com,
        rkovhaev@...il.com, straube.linux@...il.com,
        linux-staging@...ts.linux.dev,
        linux-kernel <linux-kernel@...r.kernel.org>,
        syzbot+1c46f3771695bccbdb3a@...kaller.appspotmail.com
Subject: Re: [PATCH] staging: rtl8712: Fix memory leak in r8712_init_recv_priv

On Fri, May 21, 2021 at 08:24:58PM +0800, 慕冬亮 wrote:
> On Fri, May 21, 2021 at 8:18 PM Greg KH <gregkh@...uxfoundation.org> wrote:
> >
> > On Fri, May 21, 2021 at 08:08:11PM +0800, Dongliang Mu wrote:
> > > r871xu_dev_remove failed to call r8712_free_drv_sw() and free the
> > > resource (e.g., struct urb) due to the failure of firmware loading.
> > >
> > > Fix this by invoking r8712_free_drv_sw at the failure site.
> > >
> > > Reported-by: syzbot+1c46f3771695bccbdb3a@...kaller.appspotmail.com
> > > Fixes: b4383c971bc5 ("staging: rtl8712: handle firmware load failure")
> > > Signed-off-by: Dongliang Mu <mudongliangabcd@...il.com>
> > > ---
> > >  drivers/staging/rtl8712/usb_intf.c | 13 ++++++++++---
> > >  1 file changed, 10 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/staging/rtl8712/usb_intf.c b/drivers/staging/rtl8712/usb_intf.c
> > > index dc21e7743349..a5190b4250ce 100644
> > > --- a/drivers/staging/rtl8712/usb_intf.c
> > > +++ b/drivers/staging/rtl8712/usb_intf.c
> > > @@ -589,7 +589,7 @@ static int r871xu_drv_init(struct usb_interface *pusb_intf,
> > >   */
> > >  static void r871xu_dev_remove(struct usb_interface *pusb_intf)
> > >  {
> > > -     struct net_device *pnetdev = usb_get_intfdata(pusb_intf);
> > > +     struct net_device *pnetdev, *newpnetdev = usb_get_intfdata(pusb_intf);
> > >       struct usb_device *udev = interface_to_usbdev(pusb_intf);
> > >
> > >       if (pnetdev) {
> >
> > Did you test this?
> 
> For now, I only tested this patch in my local workspace. The memory
> leak does not occur any more.
> 
> I have pushed a patch testing onto the syzbot dashboard [1]. Now it is
> in the pending state.
> 
> [1] https://syzkaller.appspot.com/bug?id=3a325b8389fc41c1bc94de0f4ac437ed13cce584
> 
> >
> > I think you just broke the code right here :(
> 
> If I broke any code logic, I am sorry. However, this patch only adds
> some code to deallocate some resources when failing to load firmware.
> 
> Do you mean that I replace pnetdev with the variable - newpnetdev?

Yes, and then the first thing the code does is check the value of
pnetdev which is totally undefined :(