iio: chemical: vz89x: prevent corrupted buffer from being read

Signed-off-by: Matt Ranostay <mranostay@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --git a/drivers/iio/chemical/vz89x.c b/drivers/iio/chemical/vz89x.c
index 289d291..cd3870e 100644 (file)
--- a/drivers/iio/chemical/vz89x.c
+++ b/drivers/iio/chemical/vz89x.c
@@ -55,6 +55,7 @@ struct vz89x_data {
        struct mutex lock;
        int (*xfer)(struct vz89x_data *data, u8 cmd);
 
+       bool is_valid;
        unsigned long last_update;
        u8 buffer[VZ89TE_REG_MEASUREMENT_RD_SIZE];
 };
@@ -229,7 +230,10 @@ static int vz89x_get_measurement(struct vz89x_data *data)
 
        /* sensor can only be polled once a second max per datasheet */
        if (!time_after(jiffies, data->last_update + HZ))
-               return 0;
+               return data->is_valid ? 0 : -EAGAIN;
+
+       data->is_valid = false;
+       data->last_update = jiffies;
 
        ret = data->xfer(data, chip->cmd);
        if (ret < 0)
@@ -239,7 +243,7 @@ static int vz89x_get_measurement(struct vz89x_data *data)
        if (ret)
                return -EAGAIN;
 
-       data->last_update = jiffies;
+       data->is_valid = true;
 
        return 0;
 }