[PATCH] mfd: mt6360: add bound check in regmap read/write function

[cy_huang]

From: ChiYuan Huang <cy_huang@xxxxxxxxxxx>

Fix the potential risk for null pointer if bank index is over the maximimum.

Refer to the discussion list for the experiment result on mt6370.
https://lore.kernel.org/all/20220914013345.GA5802@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
If not to check the bound, there is the same issue on mt6360.

Fixes: 3b0850440a06c (mfd: mt6360: Merge different sub-devices I2C read/write)
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: ChiYuan Huang <cy_huang@xxxxxxxxxxx>
---
 drivers/mfd/mt6360-core.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/mfd/mt6360-core.c b/drivers/mfd/mt6360-core.c
index 6eaa677..d375333 100644
--- a/drivers/mfd/mt6360-core.c
+++ b/drivers/mfd/mt6360-core.c
@@ -410,6 +410,9 @@ static int mt6360_regmap_read(void *context, const void *reg, size_t reg_size,
 	u8 crc;
 	int ret;
 
+	if (bank >= MT6360_SLAVE_MAX)
+		return -EINVAL;
+
 	if (bank == MT6360_SLAVE_PMIC || bank == MT6360_SLAVE_LDO) {
 		crc_needed = true;
 		ret = mt6360_xlate_pmicldo_addr(&reg_addr, val_size);
@@ -460,6 +463,9 @@ static int mt6360_regmap_write(void *context, const void *val, size_t val_size)
 	int write_size = val_size - MT6360_REGMAP_REG_BYTE_SIZE;
 	int ret;
 
+	if (bank >= MT6360_SLAVE_MAX)
+		return -EINVAL;
+
 	if (bank == MT6360_SLAVE_PMIC || bank == MT6360_SLAVE_LDO) {
 		crc_needed = true;
 		ret = mt6360_xlate_pmicldo_addr(&reg_addr, val_size - MT6360_REGMAP_REG_BYTE_SIZE);
-- 
2.7.4