staging:iio:light: V3 fix out of bounds reg_cache[] access

V3 is a straightforward forward port to teh current tree of V2.

Simple fix is to just not cache REG_TEST (offset 8).
Cache doesn't help REG_TEST anyway since we write all 8 bits exactly once
(at resume/init time).

Also fix an "off-by-one" allocation of reg_cache[] array size that
was in the original code before I touched it.

Reported-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Grant Grundler <grundler@chromium.org>
Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/staging/iio/light/isl29018.c b/drivers/staging/iio/light/isl29018.c
index f31e8c2..3e9a06c 100644 (file)
--- a/drivers/staging/iio/light/isl29018.c
+++ b/drivers/staging/iio/light/isl29018.c
@@ -51,7 +51,7 @@
 
 #define ISL29018_REG_ADD_DATA_LSB      0x02
 #define ISL29018_REG_ADD_DATA_MSB      0x03
-#define ISL29018_MAX_REGS              ISL29018_REG_ADD_DATA_MSB
+#define ISL29018_MAX_REGS              (ISL29018_REG_ADD_DATA_MSB+1)
 
 #define ISL29018_REG_TEST              0x08
 #define ISL29018_TEST_SHIFT            0
@@ -70,22 +70,27 @@ struct isl29018_chip {
 static int isl29018_write_data(struct i2c_client *client, u8 reg,
                        u8 val, u8 mask, u8 shift)
 {
-       u8 regval;
-       int ret = 0;
+       u8 regval = val;
+       int ret;
        struct isl29018_chip *chip = iio_priv(i2c_get_clientdata(client));
 
-       regval = chip->reg_cache[reg];
-       regval &= ~mask;
-       regval |= val << shift;
+       /* don't cache or mask REG_TEST */
+       if (reg < ISL29018_MAX_REGS) {
+               regval = chip->reg_cache[reg];
+               regval &= ~mask;
+               regval |= val << shift;
+       }
 
        ret = i2c_smbus_write_byte_data(client, reg, regval);
        if (ret) {
                dev_err(&client->dev, "Write to device fails status %x\n", ret);
-               return ret;
+       } else {
+               /* don't update cache on err */
+               if (reg < ISL29018_MAX_REGS)
+                       chip->reg_cache[reg] = regval;
        }
-       chip->reg_cache[reg] = regval;
 
-       return 0;
+       return ret;
 }
 
 static int isl29018_set_range(struct i2c_client *client, unsigned long range,