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From: Stephen Boyd <swboyd@chromium.org>
To: Peter Huewe <peterhuewe@gmx.de>,
	Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: linux-kernel@vger.kernel.org, Jason Gunthorpe <jgg@ziepe.ca>,
	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: [PATCH v2 1/6] hwrng: core: Freeze khwrng thread during suspend
Date: Tue, 16 Jul 2019 15:45:13 -0700
Message-ID: <20190716224518.62556-2-swboyd@chromium.org> (raw)
In-Reply-To: <20190716224518.62556-1-swboyd@chromium.org>

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.

Let's make this kthread freezable so that we don't try to touch the
hwrng during suspend/resume. This ensures that we can't cause the hwrng
backing driver to get into a bad state because the device is guaranteed
to be resumed before the hwrng kthread is thawed.

Cc: Andrey Pronin <apronin@chromium.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Duncan Laurie <dlaurie@chromium.org>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
---
 drivers/char/hw_random/core.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index 95be7228f327..3b88af3149a7 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -13,6 +13,7 @@
 #include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/err.h>
+#include <linux/freezer.h>
 #include <linux/fs.h>
 #include <linux/hw_random.h>
 #include <linux/kernel.h>
@@ -421,7 +422,9 @@ static int hwrng_fillfn(void *unused)
 {
 	long rc;
 
-	while (!kthread_should_stop()) {
+	set_freezable();
+
+	while (!kthread_freezable_should_stop(NULL)) {
 		struct hwrng *rng;
 
 		rng = get_current_rng();
-- 
Sent by a computer through tubes


  reply index

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 ` Stephen Boyd [this message]
2019-07-17  1:43   ` [PATCH v2 1/6] hwrng: core: Freeze khwrng thread during suspend 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
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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