linux-kernel - [PATCH AUTOSEL 4.19 01/13] power: supply: ab8500: Fix external_power

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Date:   Wed, 31 May 2023 09:45:29 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Hans de Goede <hdegoede@...hat.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Sebastian Reichel <sebastian.reichel@...labora.com>,
        Sasha Levin <sashal@...nel.org>, sre@...nel.org,
        linux-pm@...r.kernel.org
Subject: [PATCH AUTOSEL 4.19 01/13] power: supply: ab8500: Fix external_power_changed race

From: Hans de Goede <hdegoede@...hat.com>

[ Upstream commit a5299ce4e96f3e8930e9c051b28d8093ada87b08 ]

ab8500_btemp_external_power_changed() dereferences di->btemp_psy,
which gets sets in ab8500_btemp_probe() like this:

        di->btemp_psy = devm_power_supply_register(dev, &ab8500_btemp_desc,
                                                   &psy_cfg);

As soon as devm_power_supply_register() has called device_add()
the external_power_changed callback can get called. So there is a window
where ab8500_btemp_external_power_changed() may get called while
di->btemp_psy has not been set yet leading to a NULL pointer dereference.

Fixing this is easy. The external_power_changed callback gets passed
the power_supply which will eventually get stored in di->btemp_psy,
so ab8500_btemp_external_power_changed() can simply directly use
the passed in psy argument which is always valid.

And the same applies to ab8500_fg_external_power_changed().

Signed-off-by: Hans de Goede <hdegoede@...hat.com>
Reviewed-by: Linus Walleij <linus.walleij@...aro.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@...labora.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/power/supply/ab8500_btemp.c | 6 ++----
 drivers/power/supply/ab8500_fg.c    | 6 ++----
 2 files changed, 4 insertions(+), 8 deletions(-)

diff --git a/drivers/power/supply/ab8500_btemp.c b/drivers/power/supply/ab8500_btemp.c
index 0fd24577112eb..0bec8b90667c8 100644
--- a/drivers/power/supply/ab8500_btemp.c
+++ b/drivers/power/supply/ab8500_btemp.c
@@ -919,10 +919,8 @@ static int ab8500_btemp_get_ext_psy_data(struct device *dev, void *data)
  */
 static void ab8500_btemp_external_power_changed(struct power_supply *psy)
 {
-	struct ab8500_btemp *di = power_supply_get_drvdata(psy);
-
-	class_for_each_device(power_supply_class, NULL,
-		di->btemp_psy, ab8500_btemp_get_ext_psy_data);
+	class_for_each_device(power_supply_class, NULL, psy,
+			      ab8500_btemp_get_ext_psy_data);
 }
 
 /* ab8500 btemp driver interrupts and their respective isr */
diff --git a/drivers/power/supply/ab8500_fg.c b/drivers/power/supply/ab8500_fg.c
index 675f9d0e8471e..d0cbd7189a622 100644
--- a/drivers/power/supply/ab8500_fg.c
+++ b/drivers/power/supply/ab8500_fg.c
@@ -2380,10 +2380,8 @@ static int ab8500_fg_init_hw_registers(struct ab8500_fg *di)
  */
 static void ab8500_fg_external_power_changed(struct power_supply *psy)
 {
-	struct ab8500_fg *di = power_supply_get_drvdata(psy);
-
-	class_for_each_device(power_supply_class, NULL,
-		di->fg_psy, ab8500_fg_get_ext_psy_data);
+	class_for_each_device(power_supply_class, NULL, psy,
+			      ab8500_fg_get_ext_psy_data);
 }
 
 /**
-- 
2.39.2