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authorPavel Herrmann <morpheus.ibis@gmail.com>2011-07-17 18:39:19 +0200
committerGreg Kroah-Hartman <gregkh@suse.de>2011-08-08 10:23:07 -0700
commit166d832bd02cccddb49a1b07e71dbefc0e3e063f (patch)
treee25d54a0437a5be092af8d80c148a4e77773f61f /drivers
parentabcd4aa304268111b33daa61cb4dbe75da41b3aa (diff)
downloadlinux-linaro-stable-166d832bd02cccddb49a1b07e71dbefc0e3e063f.tar.gz
hwmon: (max1111) Fix race condition causing NULL pointer exception
commit d3f684f2820a7f42acef68bea6622d9032127fb2 upstream. spi_sync call uses its spi_message parameter to keep completion information, using a drvdata structure is not thread-safe. Use a mutex to prevent multiple access to shared driver data. 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> Tested-by: Stanislav Brabec <utx@penguin.cz> Signed-off-by: Jean Delvare <khali@linux-fr.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/hwmon/max1111.c11
1 files changed, 11 insertions, 0 deletions
diff --git a/drivers/hwmon/max1111.c b/drivers/hwmon/max1111.c
index 9ac497271adf..5b6001b5b756 100644
--- a/drivers/hwmon/max1111.c
+++ b/drivers/hwmon/max1111.c
@@ -39,6 +39,8 @@ struct max1111_data {
struct spi_transfer xfer[2];
uint8_t *tx_buf;
uint8_t *rx_buf;
+ struct mutex drvdata_lock;
+ /* protect msg, xfer and buffers from multiple access */
};
static int max1111_read(struct device *dev, int channel)
@@ -47,6 +49,9 @@ static int max1111_read(struct device *dev, int channel)
uint8_t v1, v2;
int err;
+ /* writing to drvdata struct is not thread safe, wait on mutex */
+ mutex_lock(&data->drvdata_lock);
+
data->tx_buf[0] = (channel << MAX1111_CTRL_SEL_SH) |
MAX1111_CTRL_PD0 | MAX1111_CTRL_PD1 |
MAX1111_CTRL_SGL | MAX1111_CTRL_UNI | MAX1111_CTRL_STR;
@@ -54,12 +59,15 @@ 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->drvdata_lock);
return err;
}
v1 = data->rx_buf[0];
v2 = data->rx_buf[1];
+ mutex_unlock(&data->drvdata_lock);
+
if ((v1 & 0xc0) || (v2 & 0x3f))
return -EINVAL;
@@ -175,6 +183,8 @@ static int __devinit max1111_probe(struct spi_device *spi)
if (err)
goto err_free_data;
+ mutex_init(&data->drvdata_lock);
+
data->spi = spi;
spi_set_drvdata(spi, data);
@@ -212,6 +222,7 @@ 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->drvdata_lock);
kfree(data->rx_buf);
kfree(data->tx_buf);
kfree(data);