iio: sx9310: Fix access to variable DT array

commit 6f0078ae704d94b1a93e5f3d0a44cf3d8090fa91 upstream.

With the current code, we want to read 4 entries from DT array
"semtech,combined-sensors". If there are less, we silently fail as
of_property_read_u32_array() returns -EOVERFLOW.

First count the number of entries and if between 1 and 4, collect the
content of the array.

Fixes: 5b19ca2c78a0 ("iio: sx9310: Set various settings from DT")
Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20210326184603.251683-2-gwendal@chromium.org
Cc: <stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/iio/proximity/sx9310.c b/drivers/iio/proximity/sx9310.c
index 002896e3f4b30abd169f8ba5d1f326b515490d40..ea82cfaf7f427767fa9939d46a7e538b4709d00b 100644 (file)
--- a/drivers/iio/proximity/sx9310.c
+++ b/drivers/iio/proximity/sx9310.c
@@ -1221,17 +1221,17 @@ static int sx9310_init_compensation(struct iio_dev *indio_dev)
 }
 
 static const struct sx9310_reg_default *
-sx9310_get_default_reg(struct sx9310_data *data, int i,
+sx9310_get_default_reg(struct sx9310_data *data, int idx,
                       struct sx9310_reg_default *reg_def)
 {
-       int ret;
        const struct device_node *np = data->client->dev.of_node;
-       u32 combined[SX9310_NUM_CHANNELS] = { 4, 4, 4, 4 };
+       u32 combined[SX9310_NUM_CHANNELS];
+       u32 start = 0, raw = 0, pos = 0;
        unsigned long comb_mask = 0;
+       int ret, i, count;
        const char *res;
-       u32 start = 0, raw = 0, pos = 0;
 
-       memcpy(reg_def, &sx9310_default_regs[i], sizeof(*reg_def));
+       memcpy(reg_def, &sx9310_default_regs[idx], sizeof(*reg_def));
        if (!np)
                return reg_def;
 
@@ -1242,15 +1242,31 @@ sx9310_get_default_reg(struct sx9310_data *data, int i,
                        reg_def->def |= SX9310_REG_PROX_CTRL2_SHIELDEN_GROUND;
                }
 
-               reg_def->def &= ~SX9310_REG_PROX_CTRL2_COMBMODE_MASK;
-               of_property_read_u32_array(np, "semtech,combined-sensors",
-                                          combined, ARRAY_SIZE(combined));
-               for (i = 0; i < ARRAY_SIZE(combined); i++) {
-                       if (combined[i] <= SX9310_NUM_CHANNELS)
-                               comb_mask |= BIT(combined[i]);
+               count = of_property_count_elems_of_size(np, "semtech,combined-sensors",
+                                                       sizeof(u32));
+               if (count > 0 && count <= ARRAY_SIZE(combined)) {
+                       ret = of_property_read_u32_array(np, "semtech,combined-sensors",
+                                                        combined, count);
+                       if (ret)
+                               break;
+               } else {
+                       /*
+                        * Either the property does not exist in the DT or the
+                        * number of entries is incorrect.
+                        */
+                       break;
+               }
+               for (i = 0; i < count; i++) {
+                       if (combined[i] >= SX9310_NUM_CHANNELS) {
+                               /* Invalid sensor (invalid DT). */
+                               break;
+                       }
+                       comb_mask |= BIT(combined[i]);
                }
+               if (i < count)
+                       break;
 
-               comb_mask &= 0xf;
+               reg_def->def &= ~SX9310_REG_PROX_CTRL2_COMBMODE_MASK;
                if (comb_mask == (BIT(3) | BIT(2) | BIT(1) | BIT(0)))
                        reg_def->def |= SX9310_REG_PROX_CTRL2_COMBMODE_CS0_CS1_CS2_CS3;
                else if (comb_mask == (BIT(1) | BIT(2)))