regmap-irq: Fix offset/index mismatch in read_sub_irq_data()

[ Upstream commit 3f05010f24 ]

We need to divide the sub-irq status register offset by register
stride to get an index for the status buffer to avoid an out of
bounds write when the register stride is greater than 1.

Fixes: a2d21848d9 ("regmap: regmap-irq: Add main status register support")
Signed-off-by: Aidan MacDonald <aidanmacdonald.0x0@gmail.com>
Link: https://lore.kernel.org/r/20220620200644.1961936-3-aidanmacdonald.0x0@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/base/regmap/regmap-irq.c

@@ -387,6 +387,7 @@ static inline int read_sub_irq_data(struct regmap_irq_chip_data *data,
 		subreg = &chip->sub_reg_offsets[b];
 		for (i = 0; i < subreg->num_regs; i++) {
 			unsigned int offset = subreg->offset[i];
+			unsigned int index = offset / map->reg_stride;
 
 			if (chip->not_fixed_stride)
 				ret = regmap_read(map,
@@ -395,7 +396,7 @@ static inline int read_sub_irq_data(struct regmap_irq_chip_data *data,
 			else
 				ret = regmap_read(map,
 						chip->status_base + offset,
-						&data->status_buf[offset]);
+						&data->status_buf[index]);
 
 			if (ret)
 				break;