linux-kernel - [PATCH 5.8 137/177] regulator: core: Fix slab-out-of-bounds in regulator_unlock

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Message-Id: <20200915140700.218120657@linuxfoundation.org>
Date:   Tue, 15 Sep 2020 16:13:28 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dmitry Osipenko <digetx@...il.com>,
        Mark Brown <broonie@...nel.org>
Subject: [PATCH 5.8 137/177] regulator: core: Fix slab-out-of-bounds in regulator_unlock_recursive()

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