[PATCH] mfd: syscon: Add check for invalid resource size

[Eder Zulian]

Add a consistency check to avoid assigning an invalid value to
max_register due to a possible DT misconfiguration.

Suggested-by: Mark Langsdorf <mlangsdo@xxxxxxxxxx>
Signed-off-by: Eder Zulian <ezulian@xxxxxxxxxx>
---
 drivers/mfd/syscon.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c
index 226915ca3c93..362824a7e350 100644
--- a/drivers/mfd/syscon.c
+++ b/drivers/mfd/syscon.c
@@ -47,6 +47,7 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_res)
 	struct regmap_config syscon_config = syscon_regmap_config;
 	struct resource res;
 	struct reset_control *reset;
+	resource_size_t res_size;
 
 	WARN_ON(!mutex_is_locked(&syscon_list_lock));
 
@@ -96,6 +97,12 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_res)
 		}
 	}
 
+	res_size = resource_size(&res);
+	if (res_size < reg_io_width) {
+		ret = -EFAULT;
+		goto err_regmap;
+	}
+
 	syscon_config.name = kasprintf(GFP_KERNEL, "%pOFn@%pa", np, &res.start);
 	if (!syscon_config.name) {
 		ret = -ENOMEM;
@@ -103,7 +110,7 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_res)
 	}
 	syscon_config.reg_stride = reg_io_width;
 	syscon_config.val_bits = reg_io_width * 8;
-	syscon_config.max_register = resource_size(&res) - reg_io_width;
+	syscon_config.max_register = res_size - reg_io_width;
 	if (!syscon_config.max_register)
 		syscon_config.max_register_is_0 = true;
 
-- 
2.48.1