linux-kernel - Re: [PATCH 1/2] staging: gpib: Fix NULL pointer dereference in detach

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Message-ID: <Z4vlG3xV3weJC-L4@egonzo>
Date: Sat, 18 Jan 2025 18:30:03 +0100
From: Dave Penkler <dpenkler@...il.com>
To: Greg KH <gregkh@...uxfoundation.org>
Cc: linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] staging: gpib: Fix NULL pointer dereference in detach

On Sat, Jan 18, 2025 at 04:36:15PM +0100, Greg KH wrote:
> On Sat, Jan 18, 2025 at 03:50:45PM +0100, Dave Penkler wrote:
> > When the detach function is called after a failed attach
> > the usb_dev initialization can cause a NULL pointer
> > dereference. This happens when the usb device is not found
> > in the attach procedure.
> > 
> > Remove the usb_dev variable and initialization and change the dev
> > in the dev_info message from the usb_dev to the gpib_dev.
> > 
> > Fixes: fbae7090f30c ("staging: gpib: Update messaging and usb_device refs in agilent_usb")
> > Signed-off-by: Dave Penkler <dpenkler@...il.com>
> > ---
> >  drivers/staging/gpib/agilent_82357a/agilent_82357a.c | 4 +---
> >  1 file changed, 1 insertion(+), 3 deletions(-)
> > 
> > diff --git a/drivers/staging/gpib/agilent_82357a/agilent_82357a.c b/drivers/staging/gpib/agilent_82357a/agilent_82357a.c
> > index 34d85a1bdb37..2aaccebc3c7b 100644
> > --- a/drivers/staging/gpib/agilent_82357a/agilent_82357a.c
> > +++ b/drivers/staging/gpib/agilent_82357a/agilent_82357a.c
> > @@ -1442,12 +1442,10 @@ static int agilent_82357a_go_idle(gpib_board_t *board)
> >  static void agilent_82357a_detach(gpib_board_t *board)
> >  {
> >  	struct agilent_82357a_priv *a_priv;
> > -	struct usb_device *usb_dev;
> >  
> >  	mutex_lock(&agilent_82357a_hotplug_lock);
> >  
> >  	a_priv = board->private_data;
> > -	usb_dev = interface_to_usbdev(a_priv->bus_interface);
> >  	if (a_priv) {
> >  		if (a_priv->bus_interface) {
> >  			agilent_82357a_go_idle(board);
> > @@ -1459,7 +1457,7 @@ static void agilent_82357a_detach(gpib_board_t *board)
> >  		agilent_82357a_cleanup_urbs(a_priv);
> >  		agilent_82357a_free_private(a_priv);
> >  	}
> > -	dev_info(&usb_dev->dev, "%s: detached\n", __func__);
> > +	dev_info(board->gpib_dev, "%s: detached\n", __func__);
> 
> In the future, these dev_info() lines all need to go away as when
> drivers work properly, they should be quiet.  I'll take this fix for now
> as it's needed, just something to plan on for the future cleanups here.
> 
> thanks,
> 
> greg k-h
OK
thanks,
-dave