[PATCH 5.4 100/132] regulator: core: Fix slab-out-of-bounds in regulator_unlock_recursive()

Greg Kroah-Hartman
2020-09-15T23:54:25Z

From: Dmitry Osipenko <digetx@gmail.com>

commit 0a7416f94707c60b9f66b01c0a505b7e41375f3a upstream.

The recent commit 7d8196641ee1 ("regulator: Remove pointer table
overallocation") changed the size of coupled_rdevs and now KASAN is able
to detect slab-out-of-bounds problem in regulator_unlock_recursive(),
which is a legit problem caused by a typo in the code. The recursive
unlock function uses n_coupled value of a parent regulator for unlocking
supply regulator, while supply's n_coupled should be used. In practice
problem may only affect platforms that use coupled regulators.

Cc: stable@vger.kernel.org # 5.0+
Fixes: f8702f9e4aa7 ("regulator: core: Use ww_mutex for regulators locking")
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Link: https://lore.kernel.org/r/20200831204335.19489-1-digetx@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/regulator/core.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)

--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -235,8 +235,8 @@ static bool regulator_supply_is_couple(s
static void regulator_unlock_recursive(struct regulator_dev *rdev,
unsigned int n_coupled)
{
- struct regulator_dev *c_rdev;
- int i;
+ struct regulator_dev *c_rdev, *supply_rdev;
+ int i, supply_n_coupled;

for (i = n_coupled; i > 0; i--) {
c_rdev = rdev->coupling_desc.coupled_rdevs[i - 1];
@@ -244,10 +244,13 @@ static void regulator_unlock_recursive(s
if (!c_rdev)
continue;

- if (c_rdev->supply && !regulator_supply_is_couple(c_rdev))
- regulator_unlock_recursive(
- c_rdev->supply->rdev,
- c_rdev->coupling_desc.n_coupled);
+ if (c_rdev->supply && !regulator_supply_is_couple(c_rdev)) {
+ supply_rdev = c_rdev->supply->rdev;
+ supply_n_coupled = supply_rdev->coupling_desc.n_coupled;
+
+ regulator_unlock_recursive(supply_rdev,
+ supply_n_coupled);
+ }

regulator_unlock(c_rdev);
}