linux-kernel - Re: [BUG, PATCH 03/10] sysfs: added __compat_only_sysfs_link_entry_to

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Message-ID: <20151107180856.GA2250@newt.localdomain>
Date:	Sat, 7 Nov 2015 10:08:56 -0800
From:	Jeremiah Mahler <jmmahler@...il.com>
To:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:	tpmdd-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	peterhuewe@....de, gregkh@...uxfoundation.org,
	jgunthorpe@...idianresearch.com, dhowells@...hat.com,
	artem.bityutskiy@...ux.intel.com, Tejun Heo <tj@...nel.org>,
	NeilBrown <neilb@...e.de>, Guenter Roeck <linux@...ck-us.net>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [BUG, PATCH 03/10] sysfs: added
 __compat_only_sysfs_link_entry_to_kobj()

Jarkko,

On Sat, Nov 07, 2015 at 01:41:37PM +0200, Jarkko Sakkinen wrote:
> On Sat, Nov 07, 2015 at 12:55:43PM +0200, Jarkko Sakkinen wrote:
> > On Fri, Nov 06, 2015 at 06:55:18PM -0800, Jeremiah Mahler wrote:
> > > Jarkko,
> > > 
[...]
> > > > +	entry = kernfs_find_and_get(target_kobj->sd, target_name);
> > > > +	if (!entry) {
> > > > +		kernfs_put(target);
> > > > +		return -ENOENT;
> > > > +	}
> > > > +
> > > 
> > > On an Acer C720 this call to kernfs_find_and_get fails resulting in
> > > a failed resume after suspend.
> > > 
> > > Apparently it can't find an object for the name "ppi".
> > > 
> > > This bug does not appear until the next patch is applied which
> > > calls __compat_only_sysfs_link_entry_to_kobj.
> > 
> > I think I might have found something thanks to your help
> > 
> > First I found this old bug:
> > 
> > https://bugzilla.redhat.com/show_bug.cgi?id=1096511
> > 
> > What is happening is that DSM is not found and therefore tpm_add_ppi()
> > does not add ppi to sysfs groups array.
> > 
> > __compat_only_sysfs_link_entry_to_kobj() is called after tpm_add_ppi
> > unconditionally for TPM1.
> > 
> > I'll implement a fix for this ASAP.
> > 
> > Thank you for great effort on finding tis!
> 
> I pushed a fix over here:
> 
> https://github.com/jsakkine/linux-tpmdd/tree/fixes
> 
This fix does work since it effectively avoids the call to
__compat_only_sysfs_link_entry_to_kobj().

Have you tested cases where __compat_only_sysfs_link_entry_to_kobj()
is actually used?

[...]

-- 
- Jeremiah Mahler
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