netdev - Re: [PATCH net] net: qmi_wwan: fix Oops while disconnecting

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Message-Id: <201206281040.55402.oliver@neukum.org>
Date:	Thu, 28 Jun 2012 10:40:55 +0200
From:	Oliver Neukum <oliver@...kum.org>
To:	Bjørn Mork <bjorn@...k.no>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	Ming Lei <tom.leiming@...il.com>, linux-usb@...r.kernel.org,
	Marius Bjørnstad Kotsbak 
	<marius.kotsbak@...il.com>
Subject: Re: [PATCH net] net: qmi_wwan: fix Oops while disconnecting

Am Donnerstag, 28. Juni 2012, 10:36:49 schrieb Bjørn Mork:
> Bjørn Mork <bjorn@...k.no> writes:
> 
> [..]
> > Fixes this Oops where a cdc-wdm device was closed while the
> > USB device was disconnecting, causing wdm_release to call
> > qmi_wwan_cdc_wdm_manage_power after intfdata was set to
> > NULL by usbnet_disconnect:
> >
> > [41819.087460] BUG: unable to handle kernel NULL pointer dereference at 00000080
> > [41819.087815] IP: [<f8640458>] qmi_wwan_manage_power+0x68/0x90 [qmi_wwan]
> > [41819.088028] *pdpt = 000000000314f001 *pde = 0000000000000000
> > [41819.088028] Oops: 0002 [#1] SMP
> 
> [..]
> 
> > diff --git a/drivers/net/usb/qmi_wwan.c b/drivers/net/usb/qmi_wwan.c
> > index 3767a12..b01960f 100644
> > --- a/drivers/net/usb/qmi_wwan.c
> > +++ b/drivers/net/usb/qmi_wwan.c
> > @@ -197,6 +197,10 @@ err:
> >  static int qmi_wwan_cdc_wdm_manage_power(struct usb_interface *intf, int on)
> >  {
> >  	struct usbnet *dev = usb_get_intfdata(intf);
> > +
> > +	/* can be called while disconnecting */
> > +	if (!dev)
> > +		return 0;
> >  	return qmi_wwan_manage_power(dev, on);
> >  }
> 
> Hello,
> 
> I'd like this patch applied to qmi_wwan regardless of the outcome of the
> (now stalled?) generic usbnet_disconnect discussion.
> 
> The patch fixes a real Oops in 3.4 and 3.5, and I believe it should be
> left in qmi_wwan even if the usbnet code is fixed to avoid this specific
> bug.  The additional NULL test won't harm, and it makes the code more
> robust should someone decide to rearrange usbnet_disconnect again at
> some later point in time.
> 
> I really want this fixed in the next 3.4 stable release, if possible.
> Should I resubmit the patch, or will you pick it up from
> http://patchwork.ozlabs.org/patch/166542/ ?

Yes.

David, can you please apply this? It needs to also go into stable.
We might remove this in later releases, but for now it is needed.

	Regards
		Oliver
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