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

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Message-ID: <20151201172537.GA541@obsidianresearch.com>
Date:	Tue, 1 Dec 2015 10:25:37 -0700
From:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>
To:	"Wilck, Martin" <martin.wilck@...fujitsu.com>
Cc:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>,
	"tpmdd-devel@...ts.sourceforge.net" 
	<tpmdd-devel@...ts.sourceforge.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [tpmdd-devel] [PATCH] base/platform: fix panic when probe
 function is NULL

On Tue, Dec 01, 2015 at 04:19:25PM +0100, Wilck, Martin wrote:
> > > > tpm_tis_init calls tpmm_chip_alloc which barfs when pdev (i.e. the return value
> > > > of platform_device_register_simple above) isn't bound. It is not allowed
> > > > to assume that the device is bound after the above function calls.
> > > 
> > > Can you please explain again why you think that assumption is invalid? 
> > 
> > You can unbind a device from a driver via sysfs, you can also prevent
> > binding somehow I think, probing can fail for different reasons, probing
> > might wait for userspace interaction to load firmware which wasn't
> > scheduled yet. I'm sure there are still more things that break the
> > assumption.
> 
> Thanks. Out of these, "prevent binding somehow" would be the only
> problem that applies to tpm_tis, as probing can't fail (no probe()
> routine), there's no FW to load, and unbinding via sysfs would require
> nearly impossible timing (not sure if it could be done with udev).
> 
> Anyway, the Right Thing to do is to create a probe() routine and that's
> what Jason did.

That fixes tpm_tis, but there are other ancient TPM drivers that use
the old, now broken way.

So, we still need to do something here. Either fixup b8b2c7d845d5 as
you have proposed, remove the now broken obsolete TPM drivers, or try
and fix them..

Jason
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