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

[<Mario.Limonciello@dell.com>]

> -----Original Message-----
> From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
> Sent: Wednesday, May 27, 2020 3:09 PM
> To: James Bottomley; Limonciello, Mario; peterhuewe@gmx.de; jgg@ziepe.ca
> Cc: arnd@arndb.de; gregkh@linuxfoundation.org; linux-integrity@vger.kernel.org;
> linux-kernel@vger.kernel.org; jeffrin@rajagiritech.edu.in; alex@guzman.io
> Subject: Re: [PATCH] tpm: Revert "tpm: fix invalid locking in NONBLOCKING mode"
> 
> 
> [EXTERNAL EMAIL]
> 
> 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,