From: Jason Gunthorpe <jgg@ziepe.ca>
To: Stephen Boyd <swboyd@chromium.org>
Cc: Peter Huewe <peterhuewe@gmx.de>,
Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
linux-kernel@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-integrity@vger.kernel.org,
Andrey Pronin <apronin@chromium.org>,
Duncan Laurie <dlaurie@chromium.org>,
Guenter Roeck <groeck@chromium.org>,
Herbert Xu <herbert@gondor.apana.org.au>
Subject: Re: [PATCH v2 1/6] hwrng: core: Freeze khwrng thread during suspend
Date: Wed, 17 Jul 2019 13:50:11 -0300 [thread overview]
Message-ID: <20190717165011.GI12119@ziepe.ca> (raw)
In-Reply-To: <5d2f4ff9.1c69fb81.3c314.ab00@mx.google.com>
On Wed, Jul 17, 2019 at 09:42:32AM -0700, Stephen Boyd wrote:
> Quoting Jason Gunthorpe (2019-07-17 04:39:56)
> > On Tue, Jul 16, 2019 at 03:45:13PM -0700, Stephen Boyd wrote:
> > > The hwrng_fill() function can run while devices are suspending and
> > > resuming. If the hwrng is behind a bus such as i2c or SPI and that bus
> > > is suspended, the hwrng may hang the bus while attempting to add some
> > > randomness. It's been observed on ChromeOS devices with suspend-to-idle
> > > (s2idle) and an i2c based hwrng that this kthread may run and ask the
> > > hwrng device for randomness before the i2c bus has been resumed.
> >
> > You mean the TPM here right?
>
> In my case yes, but in general it isn't the TPM.
>
> >
> > Should we be more careful in the TPM code to check if the TPM is
> > suspended before trying to use it, rather than muck up callers?
> >
>
> Given that it's not just a TPM issue I don't see how checking in the TPM
> is going to fix this problem. It's better to not try to get random bytes
> from the hwrng when the device could be suspended.
I think the same comment would apply to all the other suspend capable
hwrngs...
It just seems weird to do this, what about all the other tpm API
users? Do they have a racy problem with suspend too?
Jason
next prev parent reply other threads:[~2019-07-17 16:50 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-16 22:45 [PATCH v2 0/6] tpm: Add driver for cr50 Stephen Boyd
2019-07-16 22:45 ` [PATCH v2 1/6] hwrng: core: Freeze khwrng thread during suspend Stephen Boyd
2019-07-17 1:43 ` Herbert Xu
2019-07-17 16:36 ` Stephen Boyd
2019-07-17 11:39 ` Jason Gunthorpe
2019-07-17 16:42 ` Stephen Boyd
2019-07-17 16:50 ` Jason Gunthorpe [this message]
2019-07-17 17:03 ` Stephen Boyd
2019-08-02 22:50 ` Stephen Boyd
2019-08-16 15:56 ` Alexander Steffen
2019-08-16 23:55 ` Jarkko Sakkinen
2019-08-02 20:22 ` Jarkko Sakkinen
2019-08-02 23:18 ` Stephen Boyd
2019-07-16 22:45 ` [PATCH v2 2/6] tpm_tis_core: add optional max xfer size check Stephen Boyd
2019-07-16 22:45 ` [PATCH v2 3/6] tpm_tis_spi: add max xfer size Stephen Boyd
2019-07-17 8:07 ` Alexander Steffen
2019-07-17 18:19 ` Stephen Boyd
2019-07-16 22:45 ` [PATCH v2 4/6] dt-bindings: tpm: document properties for cr50 Stephen Boyd
2019-07-16 22:45 ` [PATCH v2 5/6] tpm: add driver for cr50 on SPI Stephen Boyd
2019-07-17 12:00 ` Alexander Steffen
2019-07-17 12:25 ` Jason Gunthorpe
2019-07-17 16:49 ` Stephen Boyd
2019-07-17 16:56 ` Jason Gunthorpe
2019-07-17 17:05 ` Stephen Boyd
2019-07-17 17:12 ` Jason Gunthorpe
2019-07-17 17:22 ` Stephen Boyd
2019-07-17 17:25 ` Jason Gunthorpe
2019-07-17 18:21 ` Stephen Boyd
2019-07-17 18:30 ` Guenter Roeck
2019-07-17 18:36 ` Jason Gunthorpe
2019-07-17 19:57 ` Stephen Boyd
2019-07-17 21:38 ` Stephen Boyd
2019-07-17 22:17 ` Stephen Boyd
2019-07-18 16:47 ` Alexander Steffen
2019-07-18 18:11 ` Stephen Boyd
2019-07-19 7:53 ` Alexander Steffen
2019-08-01 16:02 ` Stephen Boyd
2019-08-02 15:21 ` Jarkko Sakkinen
2019-08-02 18:03 ` Stephen Boyd
2019-08-02 19:43 ` Jarkko Sakkinen
2019-07-18 16:47 ` Alexander Steffen
2019-07-18 18:07 ` Stephen Boyd
2019-07-19 7:51 ` Alexander Steffen
2019-08-02 20:43 ` Jarkko Sakkinen
2019-08-02 22:32 ` Stephen Boyd
2019-08-02 20:41 ` Jarkko Sakkinen
2019-07-16 22:45 ` [PATCH v2 6/6] tpm: Add driver for cr50 on I2C Stephen Boyd
2019-07-17 15:19 ` Alexander Steffen
2019-08-05 23:52 ` Stephen Boyd
2019-08-02 20:44 ` Jarkko Sakkinen
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