regulator: core: Fix slab-out-of-bounds in regulator_unlock_recursive()

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.

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

index 5eda1927a4aa..8796c9a24b28 100644
@@ -236,8 +236,8 @@ static bool regulator_supply_is_couple(struct regulator_dev *rdev)
 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];

@@ -245,10 +245,13 @@ static void regulator_unlock_recursive(struct regulator_dev *rdev,
 		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);
 	}

2.27.0

Applied to

https://git.kernel.org/pub/scm/linux/kernel/git/broonie/regulator.git for-next

Thanks!

[1/1] regulator: core: Fix slab-out-of-bounds in regulator_unlock_recursive()

      commit: 0a7416f94707c60b9f66b01c0a505b7e41375f3a

All being well this means that it will be integrated into the linux-next tree (usually sometime in the next 24 hours) and sent to Linus during the next merge window (or sooner if it is a bug fix), however if problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing and review of the tree, please engage with people reporting problems and send followup patches addressing any issues that are reported if needed.

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Thanks,
Mark