[PATCH 07/11] power: supply: pf1550: Fix use-after-free in power_supply_changed()

[Waqar Hameed]

Using the `devm_` variant for requesting IRQ _before_ the `devm_`
variant for allocating/registering the `power_supply` handle, means that
the `power_supply` handle will be deallocated/unregistered _before_ the
interrupt handler (since `devm_` naturally deallocates in reverse
allocation order). This means that during removal, there is a race
condition where an interrupt can fire just _after_ the `power_supply`
handle has been freed, *but* just _before_ the corresponding
unregistration of the IRQ handler has run.

This will lead to the IRQ handler calling `power_supply_changed()` with
a freed `power_supply` handle. Which usually crashes the system or
otherwise silently corrupts the memory...

Note that there is a similar situation which can also happen during
`probe()`; the possibility of an interrupt firing _before_ registering
the `power_supply` handle. This would then lead to the nasty situation
of using the `power_supply` handle *uninitialized* in
`power_supply_changed()`.

Fix this racy use-after-free by making sure the IRQ is requested _after_
the registration of the `power_supply` handle.

Fixes: 4b6b6433a97d ("power: supply: pf1550: add battery charger support")
Signed-off-by: Waqar Hameed <waqar.hameed@xxxxxxxx>
---
 drivers/power/supply/pf1550-charger.c | 32 +++++++++++++--------------
 1 file changed, 16 insertions(+), 16 deletions(-)

diff --git a/drivers/power/supply/pf1550-charger.c b/drivers/power/supply/pf1550-charger.c
index 98f1ee8eca3bc..a457862ef4610 100644
--- a/drivers/power/supply/pf1550-charger.c
+++ b/drivers/power/supply/pf1550-charger.c
@@ -584,22 +584,6 @@ static int pf1550_charger_probe(struct platform_device *pdev)
 		return dev_err_probe(chg->dev, ret,
 				     "failed to add battery sense work\n");
 
-	for (i = 0; i < PF1550_CHARGER_IRQ_NR; i++) {
-		irq = platform_get_irq(pdev, i);
-		if (irq < 0)
-			return irq;
-
-		chg->virqs[i] = irq;
-
-		ret = devm_request_threaded_irq(&pdev->dev, irq, NULL,
-						pf1550_charger_irq_handler,
-						IRQF_NO_SUSPEND,
-						"pf1550-charger", chg);
-		if (ret)
-			return dev_err_probe(&pdev->dev, ret,
-					     "failed irq request\n");
-	}
-
 	psy_cfg.drv_data = chg;
 
 	chg->charger = devm_power_supply_register(&pdev->dev,
@@ -616,6 +600,22 @@ static int pf1550_charger_probe(struct platform_device *pdev)
 		return dev_err_probe(&pdev->dev, PTR_ERR(chg->battery),
 				     "failed: power supply register\n");
 
+	for (i = 0; i < PF1550_CHARGER_IRQ_NR; i++) {
+		irq = platform_get_irq(pdev, i);
+		if (irq < 0)
+			return irq;
+
+		chg->virqs[i] = irq;
+
+		ret = devm_request_threaded_irq(&pdev->dev, irq, NULL,
+						pf1550_charger_irq_handler,
+						IRQF_NO_SUSPEND,
+						"pf1550-charger", chg);
+		if (ret)
+			return dev_err_probe(&pdev->dev, ret,
+					     "failed irq request\n");
+	}
+
 	pf1550_dt_parse_dev_info(chg);
 
 	return pf1550_reg_init(chg);
-- 
2.39.5