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

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Date:   Fri, 10 Feb 2023 10:47:53 -0500
From:   Alan Stern <stern@...land.harvard.edu>
To:     Prashanth K <quic_prashk@...cinc.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Xiu Jianfeng <xiujianfeng@...wei.com>,
        Pratham Pratap <quic_ppratap@...cinc.com>,
        Jack Pham <quic_jackp@...cinc.com>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: gadget: u_serial: Add null pointer check in
 gserial_resume

On Fri, Feb 10, 2023 at 12:26:52PM +0530, Prashanth K wrote:
> 
> 
> > And this seems like a viable option to me, what do you suggest?
> > 
> > gserial_disconnect {
> >      spin_lock(static)
> >      spin_lock(port)
> >      ...
> >      gser->ioport = NULL;
> >      ...
> >      spin_lock(port)
> >      spin_unlock(static)
> > 
> > }
> > 
> > gserial_resume {
> >      struct gs_port *port = gser->ioport;
> > 
> >      spin_lock(static)
> >      if (!port)
> 	   spin_unlock(static)
> >          return
> >      spin_lock(port)

If you want, you could move the spin_unlock(static) up to here.  It 
probably doesn't matter.

> > 
> >      ...
> >      spin_unlock(port)
> >      spin_unlock(static)
> > }

I agree, that should work fine.

Alan Stern