iio: magnetometer: rm3100: add boundary check for the value read from RM3100_REG_TMRC

Recently, we encounter kernel crash in function rm3100_common_probe
caused by out of bound access of array rm3100_samp_rates (because of
underlying hardware failures). Add boundary check to prevent out of
bound access.

Fixes: 121354b2eceb ("iio: magnetometer: Add driver support for PNI RM3100")
Suggested-by: Zhouyi Zhou <zhouzhouyi@gmail.com>
Signed-off-by: zhili.liu <zhili.liu@ucas.com.cn>
Link: https://lore.kernel.org/r/1704157631-3814-1-git-send-email-zhouzhouyi@gmail.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/magnetometer/rm3100-core.c b/drivers/iio/magnetometer/rm3100-core.c
index 69938204456f8bb0c1c4777d93ee7d0b8f2421dd..42b70cd42b39359ddd542e273163cab829128ab4 100644 (file)
--- a/drivers/iio/magnetometer/rm3100-core.c
+++ b/drivers/iio/magnetometer/rm3100-core.c
@@ -530,6 +530,7 @@ int rm3100_common_probe(struct device *dev, struct regmap *regmap, int irq)
        struct rm3100_data *data;
        unsigned int tmp;
        int ret;
+       int samp_rate_index;
 
        indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
        if (!indio_dev)
@@ -586,9 +587,14 @@ int rm3100_common_probe(struct device *dev, struct regmap *regmap, int irq)
        ret = regmap_read(regmap, RM3100_REG_TMRC, &tmp);
        if (ret < 0)
                return ret;
+
+       samp_rate_index = tmp - RM3100_TMRC_OFFSET;
+       if (samp_rate_index < 0 || samp_rate_index >=  RM3100_SAMP_NUM) {
+               dev_err(dev, "The value read from RM3100_REG_TMRC is invalid!\n");
+               return -EINVAL;
+       }
        /* Initializing max wait time, which is double conversion time. */
-       data->conversion_time = rm3100_samp_rates[tmp - RM3100_TMRC_OFFSET][2]
-                               * 2;
+       data->conversion_time = rm3100_samp_rates[samp_rate_index][2] * 2;
 
        /* Cycle count values may not be what we want. */
        if ((tmp - RM3100_TMRC_OFFSET) == 0)