Re: [tpmdd-devel] [PATCH] base/platform: fix panic when probe function is NULL

[Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>]

On Sat, Nov 28, 2015 at 06:40:03PM +0200, Jarkko Sakkinen wrote:
> On Thu, Nov 26, 2015 at 01:30:31PM -0700, Jason Gunthorpe wrote:
> > On Thu, Nov 26, 2015 at 08:01:34PM +0100, martin.wilck@ts.fujitsu.com wrote:
> > > From: Martin Wilck <Martin.Wilck@ts.fujitsu.com>
> > > 
> > > Since b8b2c7d845d5, platform_drv_probe() is called for all platform
> > > devices. If drv->probe is NULL, and dev_pm_domain_attach() fails,
> > > platform_drv_probe() will return the error code from dev_pm_domain_attach().
> > > 
> > > This causes real_probe() to enter the "probe_failed" path and set
> > > dev->driver to NULL. Before b8b2c7d845d5, real_probe() would assume
> > > success if both dev->bus->probe and drv->probe are missing.
> > > 
> > > This may cause a panic later. For example, inserting the tpm_tis
> > > driver with parameter "force=1" (i.e. registering tpm_tis as a platform
> > > driver) will panic in tpmm_chip_alloc() because dev->driver is NULL:
> > > 
> > >      chip->cdev.owner = chip->pdev->driver->owner;
> > 
> > Is this happening because tpm_tis is not creating the platform device
> > properly? ie it just calls platform_device_register_simple and then
> > force initializes it via tpm_tis_init, which expects to be called from
> > a probe function with an attached driver.
> 
> Agreed. We should have a probe callback.
> 
> > Instead we should setup a proper platform device with the default
> > IO range for x86 and let the driver core call tpm_tis_init via
> > tis_drv.probe.
> > 
> > Would changing things in this way fix the problem you've observed?
> > 
> > I have some patches to do this that are part of my OF enablement
> > series, but I can make something simpler that would deal with this
> > fairly quickly if you can test.
> 
> Does the patch set that you sent include the fix or not? I haven't yet
> reviewed them properly.

Another question: does you patch series include an alternative fix for
the probe bug or should I just pick Martins fix? As I sad previously I
was seriously lost with the race but now I understand what you and
Martin were saying (and feel utterly stupid + ashamed!). Now I'm just
thinking, which fix I should pick.

Anyway, I'll try to go through your code ASAP.

/Jarkko