[PATCH] regulator: max20086: fix invalid memory access

[Cosmin Tanislav <demonsingur@gmail.com>]

max20086_parse_regulators_dt() calls of_regulator_match() using an
array of struct of_regulator_match allocated on the stack for the
matches argument.

of_regulator_match() calls devm_of_regulator_put_matches(), which calls
devres_alloc() to allocate a struct devm_of_regulator_matches which will
be de-allocated using devm_of_regulator_put_matches().

struct devm_of_regulator_matches is populated with the stack allocated
matches array.

If the device fails to probe, devm_of_regulator_put_matches() will be
called and will try to call of_node_put() on that stack pointer,
generating the following dmesg entries:

max20086 6-0028: Failed to read DEVICE_ID reg: -121
kobject: '\xc0$\xa5\x03' (000000002cebcb7a): is not initialized, yet
kobject_put() is being called.

Followed by a stack trace matching the call flow described above.

Switch to allocating the matches array using devm_kcalloc() to
avoid accessing the stack pointer long after it's out of scope.

This also has the advantage of allowing multiple max20086 to probe
without overriding the data stored inside the global of_regulator_match.

Fixes: bfff546aae50 ("regulator: Add MAX20086-MAX20089 driver")
Signed-off-by: Cosmin Tanislav <demonsingur@gmail.com>
---
 drivers/regulator/max20086-regulator.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/regulator/max20086-regulator.c b/drivers/regulator/max20086-regulator.c
index 59eb23d467ec..198d45f8e884 100644
--- a/drivers/regulator/max20086-regulator.c
+++ b/drivers/regulator/max20086-regulator.c
@@ -132,7 +132,7 @@ static int max20086_regulators_register(struct max20086 *chip)
 
 static int max20086_parse_regulators_dt(struct max20086 *chip, bool *boot_on)
 {
-	struct of_regulator_match matches[MAX20086_MAX_REGULATORS] = { };
+	struct of_regulator_match *matches;
 	struct device_node *node;
 	unsigned int i;
 	int ret;
@@ -143,6 +143,11 @@ static int max20086_parse_regulators_dt(struct max20086 *chip, bool *boot_on)
 		return -ENODEV;
 	}
 
+	matches = devm_kcalloc(chip->dev, chip->info->num_outputs,
+			       sizeof(*matches), GFP_KERNEL);
+	if (!matches)
+		return -ENOMEM;
+
 	for (i = 0; i < chip->info->num_outputs; ++i)
 		matches[i].name = max20086_output_names[i];
 
-- 
2.49.0