From: morpheus.ibis@gmail.com (Pavel Herrmann)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2] MAX1111: Fix Race condition causing NULL pointer exception
Date: Fri, 3 Jun 2011 22:00:03 +0200 [thread overview]
Message-ID: <1307131203-10845-1-git-send-email-morpheus.ibis@gmail.com> (raw)
spi_sync call uses its spi_message parameter to keep completion information,
having this structure static is not thread-safe, potentially causing one
thread having pointers to memory on or above other threads stack. use mutex
to prevent multiple access
Signed-off-by: Pavel Herrmann <morpheus.ibis@gmail.com>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Acked-by: Pavel Machek <pavel@ucw.cz>
Acked-by: Marek Vasut <marek.vasut@gmail.com>
Acked-by: Cyril Hrubis <metan@ucw.cz>
---
drivers/hwmon/max1111.c | 12 ++++++++++++
1 files changed, 12 insertions(+), 0 deletions(-)
diff --git a/drivers/hwmon/max1111.c b/drivers/hwmon/max1111.c
index 12a54aa..d872f57 100644
--- a/drivers/hwmon/max1111.c
+++ b/drivers/hwmon/max1111.c
@@ -40,6 +40,7 @@ struct max1111_data {
struct spi_transfer xfer[2];
uint8_t *tx_buf;
uint8_t *rx_buf;
+ struct mutex msg_lock_mutex;
};
static int max1111_read(struct device *dev, int channel)
@@ -48,6 +49,11 @@ static int max1111_read(struct device *dev, int channel)
uint8_t v1, v2;
int err;
+ /* spi_sync requires data not to be freed before function returns
+ * for static data, any access is dangerous, use locks
+ */
+ mutex_lock(&data->msg_lock_mutex);
+
data->tx_buf[0] = (channel << MAX1111_CTRL_SEL_SH) |
MAX1111_CTRL_PD0 | MAX1111_CTRL_PD1 |
MAX1111_CTRL_SGL | MAX1111_CTRL_UNI | MAX1111_CTRL_STR;
@@ -55,12 +61,15 @@ static int max1111_read(struct device *dev, int channel)
err = spi_sync(data->spi, &data->msg);
if (err < 0) {
dev_err(dev, "spi_sync failed with %d\n", err);
+ mutex_unlock(&data->msg_lock_mutex);
return err;
}
v1 = data->rx_buf[0];
v2 = data->rx_buf[1];
+ mutex_unlock(&data->msg_lock_mutex);
+
if ((v1 & 0xc0) || (v2 & 0x3f))
return -EINVAL;
@@ -176,6 +185,8 @@ static int __devinit max1111_probe(struct spi_device *spi)
if (err)
goto err_free_data;
+ mutex_init(&data->msg_lock_mutex);
+
data->spi = spi;
spi_set_drvdata(spi, data);
@@ -213,6 +224,7 @@ static int __devexit max1111_remove(struct spi_device *spi)
hwmon_device_unregister(data->hwmon_dev);
sysfs_remove_group(&spi->dev.kobj, &max1111_attr_group);
+ mutex_destroy(data->msg_lock_mutex);
kfree(data->rx_buf);
kfree(data->tx_buf);
kfree(data);
--
1.7.5.rc3
next reply other threads:[~2011-06-03 20:00 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-03 20:00 Pavel Herrmann [this message]
2011-06-03 22:32 ` [stable] [PATCH v2] MAX1111: Fix Race condition causing NULL pointer exception Greg KH
2011-06-29 20:11 ` Pavel Herrmann
2011-07-11 18:47 Pavel Herrmann
2011-07-11 20:11 ` Jean Delvare
2011-07-11 20:36 ` Pavel Herrmann
2011-07-11 21:03 ` Guenter Roeck
2011-07-11 21:49 ` Pavel Herrmann
2011-07-12 6:48 ` Jean Delvare
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