linux-kernel - Re: [PATCH] tpm: Fix TPM 1.2 Shutdown sequence to prevent future TPM operations

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Message-ID: <20190712115810.GA27512@ziepe.ca>
Date:   Fri, 12 Jul 2019 08:58:10 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     Douglas Anderson <dianders@...omium.org>, stable@...r.kernel.org,
        groeck@...omium.org, gregkh@...uxfoundation.org,
        sukhomlinov@...gle.com, Arnd Bergmann <arnd@...db.de>,
        Peter Huewe <peterhuewe@....de>, linux-kernel@...r.kernel.org,
        linux-integrity@...r.kernel.org
Subject: Re: [PATCH] tpm: Fix TPM 1.2 Shutdown sequence to prevent future TPM
 operations

On Fri, Jul 12, 2019 at 06:35:56AM +0300, Jarkko Sakkinen wrote:
> On Fri, Jul 12, 2019 at 06:31:38AM +0300, Jarkko Sakkinen wrote:
> > On Thu, Jul 11, 2019 at 04:46:26PM -0300, Jason Gunthorpe wrote:
> > > On Thu, Jul 11, 2019 at 10:43:13PM +0300, Jarkko Sakkinen wrote:
> > > > On Thu, Jul 11, 2019 at 09:35:33PM +0300, Jarkko Sakkinen wrote:
> > > > > > Careful with this, you can't backport this to any kernels that don't
> > > > > > have the sysfs ops locking changes or they will crash in sysfs code.
> > > > > 
> > > > > Oops, I was way too fast! Thanks Jason.
> > > > 
> > > > Hmm... hold on a second.
> > > > 
> > > > How would the crash realize? I mean this is at the point when user space
> > > > should not be active. 
> > > 
> > > Not strictly, AFAIK
> > > 
> > > > Secondly, why the crash would not realize with
> > > > TPM2? The only thing the fix is doing is to do the same thing with TPM1
> > > > essentially.
> > > 
> > > TPM2 doesn't use the unlocked sysfs path
> > 
> > Gah, sorry :-) I should have known that.
> > 
> > I can go through the patches needed when I come back from my leave after
> > two weeks.
> 
> It might require a number of patches but maybe it makes also overally sense
> to fix the racy sysfs code in stable kernels.

The sysfs isn't racy, it justs used a different locking scheme

Jason