extcon: fix extcon_get_extcon_dev() error handling

The extcon_get_extcon_dev() function returns error pointers on error and NULL when it's a -EPROBE_DEFER defer situation. There are eight callers and only two of them handled this correctly. In the other callers an error pointer return would lead to a crash.

What prevents crashes is that errors can only happen in the case of a bug in the caller or if CONFIG_EXTCON is disabled. Six out of eight callers use the Kconfig to either depend on or select CONFIG_EXTCON. Thus the real life impact of these bugs is tiny.

Signed-off-by Dan Carpenter <[email protected]>

---
The two callers where the drivers can be built without CONFIG_EXTCON are TYPEC_FUSB302 and CHARGER_MAX8997.

If we apply this patch, it might be a good idea to send it to -stable so that backported code that relies on handling error pointers does not break silently.

 drivers/extcon/extcon.c                |  2 +-
 drivers/power/supply/axp288_charger.c  | 17 ++++++++++-------
 drivers/power/supply/charger-manager.c |  7 ++-----
 drivers/power/supply/max8997_charger.c | 10 +++++-----
 drivers/usb/dwc3/drd.c                 |  9 ++-------
 drivers/usb/phy/phy-omap-otg.c         |  4 ++--
 drivers/usb/typec/tcpm/fusb302.c       |  4 ++--
 drivers/extcon/extcon-axp288.c         |  4 ++--
 8 files changed, 26 insertions(+), 31 deletions(-)

drivers/extcon/extcon.c +1 -1

index e7a9561a826d..a35e99928807 100644
@@ -876,7 +876,7 @@ struct extcon_dev *extcon_get_extcon_dev(const char *extcon_name)
 		if (!strcmp(sd->name, extcon_name))
 			goto out;
 	}
-	sd = NULL;
+	sd = ERR_PTR(-EPROBE_DEFER);
 out:
 	mutex_unlock(&extcon_dev_list_lock);
 	return sd;

drivers/power/supply/axp288_charger.c +10 -7

index ec41f6cd3f93..4acfeb52a44e 100644
@@ -848,17 +848,20 @@ static int axp288_charger_probe(struct platform_device *pdev)
 	info->regmap_irqc = axp20x->regmap_irqc;
 
 	info->cable.edev = extcon_get_extcon_dev(AXP288_EXTCON_DEV_NAME);
-	if (info->cable.edev == NULL) {
-		dev_dbg(dev, "%s is not ready, probe deferred\n",
-			AXP288_EXTCON_DEV_NAME);
-		return -EPROBE_DEFER;
+	if (IS_ERR(info->cable.edev)) {
+		dev_err_probe(dev, PTR_ERR(info->cable.edev),
+			      "extcon_get_extcon_dev(%s) failed\n",
+			      AXP288_EXTCON_DEV_NAME);
+		return PTR_ERR(info->cable.edev);
 	}
 
 	if (acpi_dev_present(USB_HOST_EXTCON_HID, NULL, -1)) {
 		info->otg.cable = extcon_get_extcon_dev(USB_HOST_EXTCON_NAME);
-		if (info->otg.cable == NULL) {
-			dev_dbg(dev, "EXTCON_USB_HOST is not ready, probe deferred\n");
-			return -EPROBE_DEFER;
+		if (IS_ERR(info->otg.cable)) {
+			dev_err_probe(dev, PTR_ERR(info->otg.cable),
+				      "extcon_get_extcon_dev(%s) failed\n",
+				      USB_HOST_EXTCON_NAME);
+			return PTR_ERR(info->otg.cable);
 		}
 		dev_info(dev, "Using " USB_HOST_EXTCON_HID " extcon for usb-id\n");
 	}

drivers/power/supply/charger-manager.c +2 -5

index d67edb760c94..92db79400a6a 100644
@@ -985,13 +985,10 @@ static int charger_extcon_init(struct charger_manager *cm,
 	cable->nb.notifier_call = charger_extcon_notifier;
 
 	cable->extcon_dev = extcon_get_extcon_dev(cable->extcon_name);
-	if (IS_ERR_OR_NULL(cable->extcon_dev)) {
+	if (IS_ERR(cable->extcon_dev)) {
 		pr_err("Cannot find extcon_dev for %s (cable: %s)\n",
 			cable->extcon_name, cable->name);
-		if (cable->extcon_dev == NULL)
-			return -EPROBE_DEFER;
-		else
-			return PTR_ERR(cable->extcon_dev);
+		return PTR_ERR(cable->extcon_dev);
 	}
 
 	for (i = 0; i < ARRAY_SIZE(extcon_mapping); i++) {

drivers/power/supply/max8997_charger.c +5 -5

index 25207fe2aa68..634658adf313 100644
@@ -248,13 +248,13 @@ static int max8997_battery_probe(struct platform_device *pdev)
 		dev_info(&pdev->dev, "couldn't get charger regulator\n");
 	}
 	charger->edev = extcon_get_extcon_dev("max8997-muic");
-	if (IS_ERR_OR_NULL(charger->edev)) {
-		if (!charger->edev)
-			return -EPROBE_DEFER;
-		dev_info(charger->dev, "couldn't get extcon device\n");
+	if (IS_ERR(charger->edev)) {
+		dev_err_probe(charger->dev, PTR_ERR(charger->edev),
+			      "couldn't get extcon device: max8997-muic\n");
+		return PTR_ERR(charger->edev);
 	}
 
-	if (!IS_ERR(charger->reg) && !IS_ERR_OR_NULL(charger->edev)) {
+	if (!IS_ERR(charger->reg)) {
 		INIT_WORK(&charger->extcon_work, max8997_battery_extcon_evt_worker);
 		ret = devm_add_action(&pdev->dev, max8997_battery_extcon_evt_stop_work, charger);
 		if (ret) {

drivers/usb/dwc3/drd.c +2 -7

index d7f76835137f..a490f79131c1 100644
@@ -454,13 +454,8 @@ static struct extcon_dev *dwc3_get_extcon(struct dwc3 *dwc)
 	 * This device property is for kernel internal use only and
 	 * is expected to be set by the glue code.
 	 */
-	if (device_property_read_string(dev, "linux,extcon-name", &name) == 0) {
-		edev = extcon_get_extcon_dev(name);
-		if (!edev)
-			return ERR_PTR(-EPROBE_DEFER);
-
-		return edev;
-	}
+	if (device_property_read_string(dev, "linux,extcon-name", &name) == 0)
+		return extcon_get_extcon_dev(name);
 
 	/*
 	 * Try to get an extcon device from the USB PHY controller's "port"

drivers/usb/phy/phy-omap-otg.c +2 -2

index ee0863c6553e..6e6ef8c0bc7e 100644
@@ -95,8 +95,8 @@ static int omap_otg_probe(struct platform_device *pdev)
 		return -ENODEV;
 
 	extcon = extcon_get_extcon_dev(config->extcon);
-	if (!extcon)
-		return -EPROBE_DEFER;
+	if (IS_ERR(extcon))
+		return PTR_ERR(extcon);
 
 	otg_dev = devm_kzalloc(&pdev->dev, sizeof(*otg_dev), GFP_KERNEL);
 	if (!otg_dev)

drivers/usb/typec/tcpm/fusb302.c +2 -2

index 7a2a17866a82..8594b59bd527 100644
@@ -1706,8 +1706,8 @@ static int fusb302_probe(struct i2c_client *client,
 	 */
 	if (device_property_read_string(dev, "linux,extcon-name", &name) == 0) {
 		chip->extcon = extcon_get_extcon_dev(name);
-		if (!chip->extcon)
-			return -EPROBE_DEFER;
+		if (IS_ERR(chip->extcon))
+			return PTR_ERR(chip->extcon);
 	}
 
 	chip->vbus = devm_regulator_get(chip->dev, "vbus");

drivers/extcon/extcon-axp288.c +2 -2

index 7c6d5857ff25..180be768c215 100644
@@ -394,8 +394,8 @@ static int axp288_extcon_probe(struct platform_device *pdev)
 		if (adev) {
 			info->id_extcon = extcon_get_extcon_dev(acpi_dev_name(adev));
 			put_device(&adev->dev);
-			if (!info->id_extcon)
-				return -EPROBE_DEFER;
+			if (IS_ERR(info->id_extcon))
+				return PTR_ERR(info->id_extcon);
 
 			dev_info(dev, "controlling USB role\n");
 		} else {

Signature · 1 line

2.20.1

The extcon_get_extcon_dev() function returns error pointers on error and NULL when it's a -EPROBE_DEFER defer situation. There are eight callers and only two of them handled this correctly. In the other callers an error pointer return would lead to a crash.

What prevents crashes is that errors can only happen in the case of a bug in the caller or if CONFIG_EXTCON is disabled. Six out of eight callers use the Kconfig to either depend on or select CONFIG_EXTCON. Thus the real life impact of these bugs is tiny.

Signed-off-by Dan Carpenter <[email protected]>

---
The two callers where the drivers can be built without CONFIG_EXTCON are TYPEC_FUSB302 and CHARGER_MAX8997.

If we apply this patch, it might be a good idea to send it to -stable so that backported code that relies on handling error pointers does not break silently.

 drivers/extcon/extcon.c                |  2 +-
 drivers/power/supply/axp288_charger.c  | 17 ++++++++++-------
 drivers/power/supply/charger-manager.c |  7 ++-----
 drivers/power/supply/max8997_charger.c | 10 +++++-----
 drivers/usb/dwc3/drd.c                 |  9 ++-------
 drivers/usb/phy/phy-omap-otg.c         |  4 ++--
 drivers/usb/typec/tcpm/fusb302.c       |  4 ++--
 drivers/extcon/extcon-axp288.c         |  4 ++--
 8 files changed, 26 insertions(+), 31 deletions(-)

drivers/extcon/extcon.c +1 -1

index e7a9561a826d..a35e99928807 100644
@@ -876,7 +876,7 @@ struct extcon_dev *extcon_get_extcon_dev(const char *extcon_name)
 		if (!strcmp(sd->name, extcon_name))
 			goto out;
 	}
-	sd = NULL;
+	sd = ERR_PTR(-EPROBE_DEFER);
 out:
 	mutex_unlock(&extcon_dev_list_lock);
 	return sd;

drivers/power/supply/axp288_charger.c +10 -7

index ec41f6cd3f93..4acfeb52a44e 100644
@@ -848,17 +848,20 @@ static int axp288_charger_probe(struct platform_device *pdev)
 	info->regmap_irqc = axp20x->regmap_irqc;
 
 	info->cable.edev = extcon_get_extcon_dev(AXP288_EXTCON_DEV_NAME);
-	if (info->cable.edev == NULL) {
-		dev_dbg(dev, "%s is not ready, probe deferred\n",
-			AXP288_EXTCON_DEV_NAME);
-		return -EPROBE_DEFER;
+	if (IS_ERR(info->cable.edev)) {
+		dev_err_probe(dev, PTR_ERR(info->cable.edev),
+			      "extcon_get_extcon_dev(%s) failed\n",
+			      AXP288_EXTCON_DEV_NAME);
+		return PTR_ERR(info->cable.edev);
 	}
 
 	if (acpi_dev_present(USB_HOST_EXTCON_HID, NULL, -1)) {
 		info->otg.cable = extcon_get_extcon_dev(USB_HOST_EXTCON_NAME);
-		if (info->otg.cable == NULL) {
-			dev_dbg(dev, "EXTCON_USB_HOST is not ready, probe deferred\n");
-			return -EPROBE_DEFER;
+		if (IS_ERR(info->otg.cable)) {
+			dev_err_probe(dev, PTR_ERR(info->otg.cable),
+				      "extcon_get_extcon_dev(%s) failed\n",
+				      USB_HOST_EXTCON_NAME);
+			return PTR_ERR(info->otg.cable);
 		}
 		dev_info(dev, "Using " USB_HOST_EXTCON_HID " extcon for usb-id\n");
 	}

drivers/power/supply/charger-manager.c +2 -5

index d67edb760c94..92db79400a6a 100644
@@ -985,13 +985,10 @@ static int charger_extcon_init(struct charger_manager *cm,
 	cable->nb.notifier_call = charger_extcon_notifier;
 
 	cable->extcon_dev = extcon_get_extcon_dev(cable->extcon_name);
-	if (IS_ERR_OR_NULL(cable->extcon_dev)) {
+	if (IS_ERR(cable->extcon_dev)) {
 		pr_err("Cannot find extcon_dev for %s (cable: %s)\n",
 			cable->extcon_name, cable->name);
-		if (cable->extcon_dev == NULL)
-			return -EPROBE_DEFER;
-		else
-			return PTR_ERR(cable->extcon_dev);
+		return PTR_ERR(cable->extcon_dev);
 	}
 
 	for (i = 0; i < ARRAY_SIZE(extcon_mapping); i++) {

drivers/power/supply/max8997_charger.c +5 -5

index 25207fe2aa68..634658adf313 100644
@@ -248,13 +248,13 @@ static int max8997_battery_probe(struct platform_device *pdev)
 		dev_info(&pdev->dev, "couldn't get charger regulator\n");
 	}
 	charger->edev = extcon_get_extcon_dev("max8997-muic");
-	if (IS_ERR_OR_NULL(charger->edev)) {
-		if (!charger->edev)
-			return -EPROBE_DEFER;
-		dev_info(charger->dev, "couldn't get extcon device\n");
+	if (IS_ERR(charger->edev)) {
+		dev_err_probe(charger->dev, PTR_ERR(charger->edev),
+			      "couldn't get extcon device: max8997-muic\n");
+		return PTR_ERR(charger->edev);
 	}
 
-	if (!IS_ERR(charger->reg) && !IS_ERR_OR_NULL(charger->edev)) {
+	if (!IS_ERR(charger->reg)) {
 		INIT_WORK(&charger->extcon_work, max8997_battery_extcon_evt_worker);
 		ret = devm_add_action(&pdev->dev, max8997_battery_extcon_evt_stop_work, charger);
 		if (ret) {

drivers/usb/dwc3/drd.c +2 -7

index d7f76835137f..a490f79131c1 100644
@@ -454,13 +454,8 @@ static struct extcon_dev *dwc3_get_extcon(struct dwc3 *dwc)
 	 * This device property is for kernel internal use only and
 	 * is expected to be set by the glue code.
 	 */
-	if (device_property_read_string(dev, "linux,extcon-name", &name) == 0) {
-		edev = extcon_get_extcon_dev(name);
-		if (!edev)
-			return ERR_PTR(-EPROBE_DEFER);
-
-		return edev;
-	}
+	if (device_property_read_string(dev, "linux,extcon-name", &name) == 0)
+		return extcon_get_extcon_dev(name);
 
 	/*
 	 * Try to get an extcon device from the USB PHY controller's "port"

drivers/usb/phy/phy-omap-otg.c +2 -2

index ee0863c6553e..6e6ef8c0bc7e 100644
@@ -95,8 +95,8 @@ static int omap_otg_probe(struct platform_device *pdev)
 		return -ENODEV;
 
 	extcon = extcon_get_extcon_dev(config->extcon);
-	if (!extcon)
-		return -EPROBE_DEFER;
+	if (IS_ERR(extcon))
+		return PTR_ERR(extcon);
 
 	otg_dev = devm_kzalloc(&pdev->dev, sizeof(*otg_dev), GFP_KERNEL);
 	if (!otg_dev)

drivers/usb/typec/tcpm/fusb302.c +2 -2

index 7a2a17866a82..8594b59bd527 100644
@@ -1706,8 +1706,8 @@ static int fusb302_probe(struct i2c_client *client,
 	 */
 	if (device_property_read_string(dev, "linux,extcon-name", &name) == 0) {
 		chip->extcon = extcon_get_extcon_dev(name);
-		if (!chip->extcon)
-			return -EPROBE_DEFER;
+		if (IS_ERR(chip->extcon))
+			return PTR_ERR(chip->extcon);
 	}
 
 	chip->vbus = devm_regulator_get(chip->dev, "vbus");

drivers/extcon/extcon-axp288.c +2 -2

index 7c6d5857ff25..180be768c215 100644
@@ -394,8 +394,8 @@ static int axp288_extcon_probe(struct platform_device *pdev)
 		if (adev) {
 			info->id_extcon = extcon_get_extcon_dev(acpi_dev_name(adev));
 			put_device(&adev->dev);
-			if (!info->id_extcon)
-				return -EPROBE_DEFER;
+			if (IS_ERR(info->id_extcon))
+				return PTR_ERR(info->id_extcon);
 
 			dev_info(dev, "controlling USB role\n");
 		} else {

The extcon_get_extcon_dev() function returns error pointers on error and NULL when it's a -EPROBE_DEFER defer situation. There are eight callers and only two of them handled this correctly. In the other callers an error pointer return would lead to a crash.

What prevents crashes is that errors can only happen in the case of a bug in the caller or if CONFIG_EXTCON is disabled. Six out of eight callers use the Kconfig to either depend on or select CONFIG_EXTCON. Thus the real life impact of these bugs is tiny.

Signed-off-by Dan Carpenter <[email protected]>

---
The two callers where the drivers can be built without CONFIG_EXTCON are TYPEC_FUSB302 and CHARGER_MAX8997.

If we apply this patch, it might be a good idea to send it to -stable so that backported code that relies on handling error pointers does not break silently.

 drivers/extcon/extcon.c                |  2 +-
 drivers/power/supply/axp288_charger.c  | 17 ++++++++++-------
 drivers/power/supply/charger-manager.c |  7 ++-----
 drivers/power/supply/max8997_charger.c | 10 +++++-----
 drivers/usb/dwc3/drd.c                 |  9 ++-------
 drivers/usb/phy/phy-omap-otg.c         |  4 ++--
 drivers/usb/typec/tcpm/fusb302.c       |  4 ++--
 drivers/extcon/extcon-axp288.c         |  4 ++--
 8 files changed, 26 insertions(+), 31 deletions(-)

drivers/extcon/extcon.c +1 -1

index e7a9561a826d..a35e99928807 100644
@@ -876,7 +876,7 @@ struct extcon_dev *extcon_get_extcon_dev(const char *extcon_name)
 		if (!strcmp(sd->name, extcon_name))
 			goto out;
 	}
-	sd = NULL;
+	sd = ERR_PTR(-EPROBE_DEFER);
 out:
 	mutex_unlock(&extcon_dev_list_lock);
 	return sd;

drivers/power/supply/axp288_charger.c +10 -7

index ec41f6cd3f93..4acfeb52a44e 100644
@@ -848,17 +848,20 @@ static int axp288_charger_probe(struct platform_device *pdev)
 	info->regmap_irqc = axp20x->regmap_irqc;
 
 	info->cable.edev = extcon_get_extcon_dev(AXP288_EXTCON_DEV_NAME);
-	if (info->cable.edev == NULL) {
-		dev_dbg(dev, "%s is not ready, probe deferred\n",
-			AXP288_EXTCON_DEV_NAME);
-		return -EPROBE_DEFER;
+	if (IS_ERR(info->cable.edev)) {
+		dev_err_probe(dev, PTR_ERR(info->cable.edev),
+			      "extcon_get_extcon_dev(%s) failed\n",
+			      AXP288_EXTCON_DEV_NAME);
+		return PTR_ERR(info->cable.edev);
 	}
 
 	if (acpi_dev_present(USB_HOST_EXTCON_HID, NULL, -1)) {
 		info->otg.cable = extcon_get_extcon_dev(USB_HOST_EXTCON_NAME);
-		if (info->otg.cable == NULL) {
-			dev_dbg(dev, "EXTCON_USB_HOST is not ready, probe deferred\n");
-			return -EPROBE_DEFER;
+		if (IS_ERR(info->otg.cable)) {
+			dev_err_probe(dev, PTR_ERR(info->otg.cable),
+				      "extcon_get_extcon_dev(%s) failed\n",
+				      USB_HOST_EXTCON_NAME);
+			return PTR_ERR(info->otg.cable);
 		}
 		dev_info(dev, "Using " USB_HOST_EXTCON_HID " extcon for usb-id\n");
 	}

drivers/power/supply/charger-manager.c +2 -5

index d67edb760c94..92db79400a6a 100644
@@ -985,13 +985,10 @@ static int charger_extcon_init(struct charger_manager *cm,
 	cable->nb.notifier_call = charger_extcon_notifier;
 
 	cable->extcon_dev = extcon_get_extcon_dev(cable->extcon_name);
-	if (IS_ERR_OR_NULL(cable->extcon_dev)) {
+	if (IS_ERR(cable->extcon_dev)) {
 		pr_err("Cannot find extcon_dev for %s (cable: %s)\n",
 			cable->extcon_name, cable->name);
-		if (cable->extcon_dev == NULL)
-			return -EPROBE_DEFER;
-		else
-			return PTR_ERR(cable->extcon_dev);
+		return PTR_ERR(cable->extcon_dev);
 	}
 
 	for (i = 0; i < ARRAY_SIZE(extcon_mapping); i++) {

drivers/power/supply/max8997_charger.c +5 -5

index 25207fe2aa68..634658adf313 100644
@@ -248,13 +248,13 @@ static int max8997_battery_probe(struct platform_device *pdev)
 		dev_info(&pdev->dev, "couldn't get charger regulator\n");
 	}
 	charger->edev = extcon_get_extcon_dev("max8997-muic");
-	if (IS_ERR_OR_NULL(charger->edev)) {
-		if (!charger->edev)
-			return -EPROBE_DEFER;
-		dev_info(charger->dev, "couldn't get extcon device\n");
+	if (IS_ERR(charger->edev)) {
+		dev_err_probe(charger->dev, PTR_ERR(charger->edev),
+			      "couldn't get extcon device: max8997-muic\n");
+		return PTR_ERR(charger->edev);
 	}
 
-	if (!IS_ERR(charger->reg) && !IS_ERR_OR_NULL(charger->edev)) {
+	if (!IS_ERR(charger->reg)) {
 		INIT_WORK(&charger->extcon_work, max8997_battery_extcon_evt_worker);
 		ret = devm_add_action(&pdev->dev, max8997_battery_extcon_evt_stop_work, charger);
 		if (ret) {

drivers/usb/dwc3/drd.c +2 -7

index d7f76835137f..a490f79131c1 100644
@@ -454,13 +454,8 @@ static struct extcon_dev *dwc3_get_extcon(struct dwc3 *dwc)
 	 * This device property is for kernel internal use only and
 	 * is expected to be set by the glue code.
 	 */
-	if (device_property_read_string(dev, "linux,extcon-name", &name) == 0) {
-		edev = extcon_get_extcon_dev(name);
-		if (!edev)
-			return ERR_PTR(-EPROBE_DEFER);
-
-		return edev;
-	}
+	if (device_property_read_string(dev, "linux,extcon-name", &name) == 0)
+		return extcon_get_extcon_dev(name);
 
 	/*
 	 * Try to get an extcon device from the USB PHY controller's "port"

drivers/usb/phy/phy-omap-otg.c +2 -2

index ee0863c6553e..6e6ef8c0bc7e 100644
@@ -95,8 +95,8 @@ static int omap_otg_probe(struct platform_device *pdev)
 		return -ENODEV;
 
 	extcon = extcon_get_extcon_dev(config->extcon);
-	if (!extcon)
-		return -EPROBE_DEFER;
+	if (IS_ERR(extcon))
+		return PTR_ERR(extcon);
 
 	otg_dev = devm_kzalloc(&pdev->dev, sizeof(*otg_dev), GFP_KERNEL);
 	if (!otg_dev)

drivers/usb/typec/tcpm/fusb302.c +2 -2

index 7a2a17866a82..8594b59bd527 100644
@@ -1706,8 +1706,8 @@ static int fusb302_probe(struct i2c_client *client,
 	 */
 	if (device_property_read_string(dev, "linux,extcon-name", &name) == 0) {
 		chip->extcon = extcon_get_extcon_dev(name);
-		if (!chip->extcon)
-			return -EPROBE_DEFER;
+		if (IS_ERR(chip->extcon))
+			return PTR_ERR(chip->extcon);
 	}
 
 	chip->vbus = devm_regulator_get(chip->dev, "vbus");

drivers/extcon/extcon-axp288.c +2 -2

index 7c6d5857ff25..180be768c215 100644
@@ -394,8 +394,8 @@ static int axp288_extcon_probe(struct platform_device *pdev)
 		if (adev) {
 			info->id_extcon = extcon_get_extcon_dev(acpi_dev_name(adev));
 			put_device(&adev->dev);
-			if (!info->id_extcon)
-				return -EPROBE_DEFER;
+			if (IS_ERR(info->id_extcon))
+				return PTR_ERR(info->id_extcon);
 
 			dev_info(dev, "controlling USB role\n");
 		} else {

Signature · 1 line

2.20.1

The extcon_get_extcon_dev() function returns error pointers on error and NULL when it's a -EPROBE_DEFER defer situation. There are eight callers and only two of them handled this correctly. In the other callers an error pointer return would lead to a crash.

What prevents crashes is that errors can only happen in the case of a bug in the caller or if CONFIG_EXTCON is disabled. Six out of eight callers use the Kconfig to either depend on or select CONFIG_EXTCON. Thus the real life impact of these bugs is tiny.

Signed-off-by Dan Carpenter <[email protected]>

---
The two callers where the drivers can be built without CONFIG_EXTCON are TYPEC_FUSB302 and CHARGER_MAX8997.

Quoted 15 lines · Dan Carpenter

The extcon_get_extcon_dev() function returns error pointers on error and NULL when it's a -EPROBE_DEFER defer situation. There are eight callers and only two of them handled this correctly. In the other callers an error pointer return would lead to a crash.

What prevents crashes is that errors can only happen in the case of a bug in the caller or if CONFIG_EXTCON is disabled. Six out of eight callers use the Kconfig to either depend on or select CONFIG_EXTCON. Thus the real life impact of these bugs is tiny.

Signed-off-by Dan Carpenter <[email protected]>

---
The two callers where the drivers can be built without CONFIG_EXTCON are TYPEC_FUSB302 and CHARGER_MAX8997.

[ ... ]

drivers/usb/typec/tcpm/fusb302.c static int fusb302_probe(struct i2c_client *client, · line 1710

Quoted 12 lines

drivers/usb/typec/tcpm/fusb302.c +2 -2

index 7a2a17866a82..8594b59bd527 100644
@@ -1706,8 +1706,8 @@ static int fusb302_probe(struct i2c_client *client,
  	 */
  	if (device_property_read_string(dev, "linux,extcon-name", &name) == 0) {
  		chip->extcon = extcon_get_extcon_dev(name);
-		if (!chip->extcon)
-			return -EPROBE_DEFER;
+		if (IS_ERR(chip->extcon))
+			return PTR_ERR(chip->extcon);

Why does the code not need to return -EPROBE_DEFER ? The description states that NULL is returned in that situation. Doesn't that mean that defer situations are no longer handled with this patch in place ?

Also, with this patch in place, the code will no longer work if extcon is disabled, because extcon_get_extcon_dev() will return -ENODEV and the above code will bail out. The behavior of the code wasn't optimal in that case (it would wait until timeout in tcpm_get_current_limit() before returning), but at least it didn't fail.

Quoted 17 lines · Guenter Roeck

Quoted 15 lines · Dan Carpenter

The extcon_get_extcon_dev() function returns error pointers on error and NULL when it's a -EPROBE_DEFER defer situation. There are eight callers and only two of them handled this correctly. In the other callers an error pointer return would lead to a crash.

What prevents crashes is that errors can only happen in the case of a bug in the caller or if CONFIG_EXTCON is disabled. Six out of eight callers use the Kconfig to either depend on or select CONFIG_EXTCON. Thus the real life impact of these bugs is tiny.

Signed-off-by Dan Carpenter <[email protected]>

---
The two callers where the drivers can be built without CONFIG_EXTCON are TYPEC_FUSB302 and CHARGER_MAX8997.

[ ... ]

Quoted 16 lines

drivers/usb/typec/tcpm/fusb302.c static int fusb302_probe(struct i2c_client *client, · line 1710

Quoted 12 lines

drivers/usb/typec/tcpm/fusb302.c +2 -2

index 7a2a17866a82..8594b59bd527 100644
@@ -1706,8 +1706,8 @@ static int fusb302_probe(struct i2c_client *client,
  	 */
  	if (device_property_read_string(dev, "linux,extcon-name", &name) == 0) {
  		chip->extcon = extcon_get_extcon_dev(name);
-		if (!chip->extcon)
-			return -EPROBE_DEFER;
+		if (IS_ERR(chip->extcon))
+			return PTR_ERR(chip->extcon);

Why does the code not need to return -EPROBE_DEFER ? The description states that NULL is returned in that situation. Doesn't that mean that defer situations are no longer handled with this patch in place ?

I'm not sure I understand what you are saying here. In the original code, extcon_get_extcon_dev() would return NULL and relied on the callers to change NULL into a -EPROBE_DEFER. If extcon_get_extcon_dev() returned ERR_PTR(-EINVAL) (which is impossible as mentioned) the it would lead to a crash.

In the new code, the extcon_get_extcon_dev() function returns -EPROBE_DEFER directly so the caller code is much simpler.

Quoted 5 lines

Also, with this patch in place, the code will no longer work if extcon is disabled, because extcon_get_extcon_dev() will return -ENODEV and the above code will bail out. The behavior of the code wasn't optimal in that case (it would wait until timeout in tcpm_get_current_limit() before returning), but at least it didn't fail.

Huh. You are right. Initialy I thought that tcpm_get_current_limit() would crash. This is one of the two drivers which I mentioned that can be built without CONFIG_EXTCON.

I will modify the version of extcon_get_extcon_dev() where CONFIG_EXTCON is disabled to return NULL. That is the standard/correct way to write these. That will turn tcpm_get_current_limit() into a no-op.

A belt and suspenders approach might be to modify the Kconfig so this driver selects CONFIG_EXTCON.

regards,
dan carpenter