linux-kernel - Re: [PATCH V3] drivers/uio/uio_pci_generic.c: allow access for non-privileged processes

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Date:	Wed, 21 Apr 2010 13:30:17 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	"Hans J. Koch" <hjk@...utronix.de>
Cc:	Tom Lyon <pugs@...co.com>, gregkh@...e.de, chrisw@...s-sol.org,
	joro@...tes.org, avi@...hat.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3] drivers/uio/uio_pci_generic.c: allow access for
	non-privileged processes

On Wed, Apr 21, 2010 at 12:31:50PM +0200, Hans J. Koch wrote:
> On Wed, Apr 21, 2010 at 12:38:49PM +0300, Michael S. Tsirkin wrote:
> > 
> > > +			j++;
> > > +		}
> > > +	}
> > > +	for (i = 0, j = 0; i < PCI_STD_RESOURCE_END &&
> > > +			   j < MAX_UIO_PORT_REGIONS; i++) {
> > > +		if (pci_resource_flags(pdev, i) & IORESOURCE_IO) {
> > > +			name = kmalloc(8, GFP_KERNEL);
> > > +			if (name == NULL)
> > > +				break;
> > > +			sprintf(name, "iobar%d", i);
> > > +			info->port[j].name = name;
> > > +			info->port[j].start = pci_resource_start(pdev, i);
> > > +			info->port[j].size = pci_resource_len(pdev, i);
> > > +			info->port[j].porttype = UIO_PORT_X86;
> > > +			j++;
> > 
> > At least on x86, I think io bar can not be mmapped.
> 
> That's right. porttype == UIO_PORT_X86 is only there for information
> purposes. Userspace then knows that it cannot map this but has to use
> things like inb(), outb() and friends after getting access rights with
> ioperm()/iopl(). "start" and "size" gives userspace the information
> needed to do this.
> 
> Thanks,
> Hans

So that fails in the declared purpose of allowing an unpriveledged
userspace driver, as inb/outb are priveledged operations.

-- 
MST
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