Re: [PATCH] drm/vboxvideo: Unmap iomem on probe-failure and remove

[Dan Carpenter <dan.carpenter@oracle.com>]

On Thu, Nov 19, 2020 at 08:30:59PM +0100, Daniel Vetter wrote:
> On Thu, Nov 19, 2020 at 6:51 PM Dan Carpenter <dan.carpenter@oracle.com> wrote:
> >
> > On Thu, Nov 19, 2020 at 12:35:56PM +0100, Hans de Goede wrote:
> > > Hi,
> > >
> > > On 10/27/20 2:51 PM, Hans de Goede wrote:
> > > > Add missing pci_iounmap() calls to properly unmap the memory on
> > > > probe-failure and remove.
> > > >
> > > > Reported-by: kernel test robot <lkp@intel.com>
> > > > Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> > > > Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> > >
> > > For some reason the spam-filter used by Red Hat's email system has eaten
> > > Daniel Vetter's reply to this, so let me copy and paste that from patchwork:
> > >
> > > Daniel Vetter wrote:
> > >
> > > > I think switching over to devm would be really nice. And for pci all
> > > > you need to do is use pcim_enable_device and delete all the cleanup
> > > > code, and it's all done. Hand rolling device cleanup code really isn't
> > > > a great idea and way too error-prone. Plus you're using lots of devm_
> > > > already.
> > >
> > > Good point, so I just checked and the vboxvideo code is already
> > > using pcim_enable_device() so it looks like this is a false-positive
> > > from the lkp@intel.com bot, and Dan Carpenter missed that pcim_enable_device()
> > > makes all subsequent pci-resource acquiring calls behave like devm calls,
> > > when he forwarded the report to me.
> > >
> > > Tl;DR: there is no bug / leak and this patch can be dropped.
> > >
> > > Is there a place where I can report a bug against the lkp@intel.com bot
> > > for this false-positive ?
> >
> > Ah.  Thanks!
> >
> > This is a Smatch bug.  There is a list for that smatch@vger.kernel.org
> > but I already remove the pci_iomap() from the list of functions that
> > needs to be unwound based on your report.
> 
> I guess if smatch sees a pci_enable_device but not pcim_enable_device
> on the same device as passed to pci_iomap (and a pile of other pci
> functions) then it still must be unwound. Could smatch detect that?
> There's a lot of pci drivers not using the managed functions, catching
> bugs in these would be good.

It's a lot of code.  There would be two ways to implement this:

1) Somehow store the links to figure out the value of:

	 devres_find(vbox->ddev.pdev.dev)->enabled

That's very complicated.  I'm sort of working on some of the steps
involved but and it's probably a multi year process before it's
possible.

2) Create a data base table with driver data, then store if the driver
calls pcim_enable_device().  This is still a bit of work, but probably
straight forward.  Storing driver data would be useful for other things
as well.

regards,
dan carpenter
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