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hwmon: (max1111) Fix race condition causing NULL pointer exception 

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>
Cc: stable@kernel.org
This commit is contained in:
Pavel Herrmann 2011-07-17 18:39:19 +02:00 committed by Jean Delvare
parent fa8b69758e
commit d3f684f282
1 changed files with 11 additions and 0 deletions
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11
drivers/hwmon/max1111.c
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@ -40,6 +40,8 @@ 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)
@ -48,6 +50,9 @@ 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;
@ -55,12 +60,15 @@ 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;
@ -176,6 +184,8 @@ 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);
@ -213,6 +223,7 @@ 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);