Re: [PATCH] tpm: Revert "tpm: fix invalid locking in NONBLOCKING mode"

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

On Thu, May 28, 2020 at 12:59:59AM +0000, Mario.Limonciello@dell.com wrote:
> > > > [EXTERNAL EMAIL]
> > 
> > What is this?
> 
> Something my employer's mail system automatically tags in external email.
> 
> My mistakes in forgetting to remove it on the response.

NP, just asking :-)

> > > > On Tue, 2020-05-26 at 12:38 -0700, James Bottomley wrote:
> > > > > On Tue, 2020-05-26 at 19:23 +0000, Mario.Limonciello@dell.com wrote:
> > > > > > > On Tue, 2020-05-26 at 13:32 -0500, Mario Limonciello wrote:
> > > > > > > > This reverts commit d23d12484307b40eea549b8a858f5fffad913897.
> > > > > > > >
> > > > > > > > This commit has caused regressions for the XPS 9560 containing
> > > > > > > > a Nuvoton TPM.
> > > > > > >
> > > > > > > Presumably this is using the tis driver?
> > > > > >
> > > > > > Correct.
> > > > > >
> > > > > > > > As mentioned by the reporter all TPM2 commands are failing with:
> > > > > > > >   ERROR:tcti:src/tss2-tcti/tcti-
> > > > > > > > device.c:290:tcti_device_receive()
> > > > > > > >   Failed to read response from fd 3, got errno 1: Operation not
> > > > > > > > permitted
> > > > > > > >
> > > > > > > > The reporter bisected this issue back to this commit which was
> > > > > > > > backported to stable as commit 4d6ebc4.
> > > > > > >
> > > > > > > I think the problem is request_locality ... for some inexplicable
> > > > > > > reason a failure there returns -1, which is EPERM to user space.
> > > > > > >
> > > > > > > That seems to be a bug in the async code since everything else
> > > > > > > gives a ESPIPE error if tpm_try_get_ops fails ... at least no-one
> > > > > > > assumes it gives back a sensible return code.
> > > > > > >
> > > > > > > What I think is happening is that with the patch the TPM goes
> > > > > > > through a quick sequence of request, relinquish, request,
> > > > > > > relinquish and it's the third request which is failing (likely
> > > > > > > timing out).  Without the patch, the patch there's only one
> > > > > > > request,relinquish cycle because the ops are held while the async
> > > > > > > work is executed.  I have a vague recollection that there is a
> > > > > > > problem with too many locality request in quick succession, but
> > > > > > > I'll defer to Jason, who I think understands the intricacies of
> > > > > > > localities better than I do.
> > > > > >
> > > > > > Thanks, I don't pretend to understand the nuances of this particular
> > > > > > code, but I was hoping that the request to revert got some attention
> > > > > > since Alex's kernel Bugzilla and message a few months ago to linux
> > > > > > integrity weren't.
> > > > > >
> > > > > > > If that's the problem, the solution looks simple enough: just move
> > > > > > > the ops get down because the priv state is already protected by the
> > > > > > > buffer mutex
> > > > > >
> > > > > > Yeah, if that works for Alex's situation it certainly sounds like a
> > > > > > better solution than reverting this patch as this patch actually does
> > > > > > fix a problem reported by Jeffrin originally.
> > > > > >
> > > > > > Could you propose a specific patch that Alex and Jeffrin can perhaps
> > > > > > both try?
> > > > >
> > > > > Um, what's wrong with the one I originally attached and which you quote
> > > > > below?  It's only compile tested, but I think it will work, if the
> > > > > theory is correct.
> > > >
> > > > Please send a legit patch, thanks.
> > > >
> > > > /Jarkko
> > >
> > > Jarkko,
> > >
> > > After the confirmation from Alex that this patch attached to the end of the
> > thread
> > > worked, James did send a proper patch that can be accessed here:
> > > https://lore.kernel.org/linux-
> > integrity/20200527155800.ya43xm2ltuwduwjg@cantor/T/#t
> > >
> > > Thanks,
> > 
> > Hi thanks a lot! I did read the full discussions and agree with the
> > conclusions as I get a patch in proper form.
> > 
> > Please ping next time a bit earlier. It's not that I don't want to deal
> > with the issues quickly as possible. It's probably just that I've forgot
> > something or missed.
> > 
> > /Jarkko
> 
> Thanks!
> 
> I completely forgot about it too, it was mentioned to me right after holidays
> and I forgot to follow up and see that it got sorted.

Yeah, sure, lets try to get a fix landed asap :-)

/Jarkko