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Subject[PATCH v2] mfd: mt6360: add bound check in regmap read/write function
Date
From: ChiYuan Huang <cy_huang@richtek.com>

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

Refer to the discussion list for the experiment result on mt6370.
https://lore.kernel.org/all/20220914013345.GA5802@cyhuang-hp-elitebook-840-g3.rt/
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@vger.kernel.org
Signed-off-by: ChiYuan Huang <cy_huang@richtek.com>
---
Since v2:
- Assign i2c bank variable after bank index is already checked.

---
drivers/mfd/mt6360-core.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/mfd/mt6360-core.c b/drivers/mfd/mt6360-core.c
index 6eaa677..d3b32eb 100644
--- a/drivers/mfd/mt6360-core.c
+++ b/drivers/mfd/mt6360-core.c
@@ -402,7 +402,7 @@ static int mt6360_regmap_read(void *context, const void *reg, size_t reg_size,
struct mt6360_ddata *ddata = context;
u8 bank = *(u8 *)reg;
u8 reg_addr = *(u8 *)(reg + 1);
- struct i2c_client *i2c = ddata->i2c[bank];
+ struct i2c_client *i2c;
bool crc_needed = false;
u8 *buf;
int buf_len = MT6360_ALLOC_READ_SIZE(val_size);
@@ -410,6 +410,11 @@ 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;
+
+ i2c = ddata->i2c[bank];
+
if (bank == MT6360_SLAVE_PMIC || bank == MT6360_SLAVE_LDO) {
crc_needed = true;
ret = mt6360_xlate_pmicldo_addr(&reg_addr, val_size);
@@ -453,13 +458,18 @@ static int mt6360_regmap_write(void *context, const void *val, size_t val_size)
struct mt6360_ddata *ddata = context;
u8 bank = *(u8 *)val;
u8 reg_addr = *(u8 *)(val + 1);
- struct i2c_client *i2c = ddata->i2c[bank];
+ struct i2c_client *i2c;
bool crc_needed = false;
u8 *buf;
int buf_len = MT6360_ALLOC_WRITE_SIZE(val_size);
int write_size = val_size - MT6360_REGMAP_REG_BYTE_SIZE;
int ret;

+ if (bank >= MT6360_SLAVE_MAX)
+ return -EINVAL;
+
+ i2c = ddata->i2c[bank];
+
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
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