linux-kernel - Re: [PATCH v2] tpm: Allow system suspend to continue when TPM suspend fails

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Date:   Sat, 21 Jan 2023 00:07:08 +0000
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     Thorsten Leemhuis <regressions@...mhuis.info>,
        James Bottomley <James.Bottomley@...senpartnership.com>,
        Peter Huewe <peterhuewe@....de>,
        Jason Gunthorpe <jgg@...pe.ca>, Jan Dabros <jsd@...ihalf.com>,
        regressions@...ts.linux.dev, LKML <linux-kernel@...r.kernel.org>,
        linux-integrity@...r.kernel.org,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Johannes Altmanninger <aclopte@...il.com>,
        stable@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>
Subject: Re: [PATCH v2] tpm: Allow system suspend to continue when TPM
 suspend fails

On Mon, Jan 16, 2023 at 03:03:17PM +0100, Jason A. Donenfeld wrote:
> Hi Jarkko,
> 
> On Mon, Jan 16, 2023 at 9:12 AM Jarkko Sakkinen <jarkko@...nel.org> wrote:
> > > diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
> > > index d69905233aff..6df9067ef7f9 100644
> > > --- a/drivers/char/tpm/tpm-interface.c
> > > +++ b/drivers/char/tpm/tpm-interface.c
> > > @@ -412,7 +412,10 @@ int tpm_pm_suspend(struct device *dev)
> > >       }
> > >
> > >  suspended:
> > > -     return rc;
> > > +     if (rc)
> > > +             pr_err("Unable to suspend tpm-%d (error %d), but continuing system suspend\n",
> > > +                    chip->dev_num, rc);
> > > +     return 0;
> > >  }
> > >  EXPORT_SYMBOL_GPL(tpm_pm_suspend);
> > >
> > > --
> > > 2.39.0
> > >
> >
> > Let me read all the threads through starting from the original report. I've
> > had emails piling up because of getting sick before holiday, and holiday
> > season after that.
> >
> > This looks sane
> 
> No, not really. I mean, it was sane under the circumstances of, "I'm
> not going to spend time fixing this for real if the maintainers aren't
> around," and it fixed the suspend issue. But it doesn't actually fix
> any real tpm issue. The real issue, AFAICT, is there's some sort of
> race between the tpm rng read command and either suspend or wakeup or
> selftest. One of these is missing some locking. And then commands step
> on each other and the tpm gets upset. This is probably something that
> should be fixed. I assume the "Fixes: ..." tag will actually go quite
> far back, with recent things only unearthing a somewhat old bug. But
> just a hunch.
> 
> Jason

See my response to Vlastimil:

https://lore.kernel.org/linux-integrity/Y8sr7YJ8e8eSpPFv@kernel.org/

Can you try what happens if you do not call tpm_add_hwrng()?

BR, Jarkko