linux-kernel - Re: [PATCH V3 04/12] misc: xilinx_sdfec: Add open, close and ioctl

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Date:   Sat, 4 May 2019 11:02:03 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Dragan Cvetic <draganc@...inx.com>
Cc:     "arnd@...db.de" <arnd@...db.de>, Michal Simek <michals@...inx.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Derek Kiernan <dkiernan@...inx.com>
Subject: Re: [PATCH V3 04/12] misc: xilinx_sdfec: Add open, close and ioctl

On Fri, May 03, 2019 at 04:44:57PM +0000, Dragan Cvetic wrote:
> > -----Original Message-----
> > From: Greg KH [mailto:gregkh@...uxfoundation.org]
> > Sent: Thursday 2 May 2019 18:23
> > To: Dragan Cvetic <draganc@...inx.com>
> > Cc: arnd@...db.de; Michal Simek <michals@...inx.com>; linux-arm-kernel@...ts.infradead.org; robh+dt@...nel.org;
> > mark.rutland@....com; devicetree@...r.kernel.org; linux-kernel@...r.kernel.org; Derek Kiernan <dkiernan@...inx.com>
> > Subject: Re: [PATCH V3 04/12] misc: xilinx_sdfec: Add open, close and ioctl
> > 
> > On Sat, Apr 27, 2019 at 11:04:58PM +0100, Dragan Cvetic wrote:
> > > +static int xsdfec_dev_open(struct inode *iptr, struct file *fptr)
> > > +{
> > > +	struct xsdfec_dev *xsdfec;
> > > +
> > > +	xsdfec = container_of(iptr->i_cdev, struct xsdfec_dev, xsdfec_cdev);
> > > +
> > > +	if (!atomic_dec_and_test(&xsdfec->open_count)) {
> > 
> > Why do you care about this?
> > 
> > And do you really think it matters?  What are you trying to protect from
> > here?
> 
> There is a request to increase the driver security. 

How does this affect "security" in any way?

> It is acceptable for us for now, even with non-perfections (will not
> be protected if opened twice with dup() or fork()).  This is covered
> in the documentation.

As this really "does nothing", no need to bother the kernel with trying
to keep this logic working properly.  So please just drop it.

thanks,

greg k-h