From fb0e28cdb20ed90f2e14b8ef5ef1befc4e04b3fe Mon Sep 17 00:00:00 2001 From: Pavel Herrmann Date: Sun, 17 Jul 2011 18:39:19 +0200 Subject: [PATCH] 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 Acked-by: Russell King Acked-by: Pavel Machek Acked-by: Marek Vasut Acked-by: Cyril Hrubis Tested-by: Stanislav Brabec Signed-off-by: Jean Delvare Signed-off-by: Greg Kroah-Hartman --- drivers/hwmon/max1111.c | 11 +++++++++++ 1 file changed, 11 insertions(+) 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); -- 2.39.5