[PATCH v2] net: phy: phy_led_triggers: Fix a possible null-pointer dereference in phy_led_trigger_change_speed()

[PATCH v2] net: phy: phy_led_triggers: Fix a possible null-pointer dereference in phy_led_trigger_change_speed()

[Jia-Ju Bai]

In phy_led_trigger_change_speed(), there is an if statement on line 48
to check whether phy->last_triggered is NULL: 
    if (!phy->last_triggered)

When phy->last_triggered is NULL, it is used on line 52:
    led_trigger_event(&phy->last_triggered->trigger, LED_OFF);

Thus, a possible null-pointer dereference may occur.

To fix this bug, led_trigger_event(&phy->last_triggered->trigger,
LED_OFF) is called when phy->last_triggered is not NULL.

This bug is found by a static analysis tool STCheck written by
the OSLAB group in Tsinghua University.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
v2:
* Add the organization of the tool's authors.
  Thank David and Andrew for helpful advice.

---
 drivers/net/phy/phy_led_triggers.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/phy/phy_led_triggers.c b/drivers/net/phy/phy_led_triggers.c
index b86a4b2116f8..59a94e07e7c5 100644
--- a/drivers/net/phy/phy_led_triggers.c
+++ b/drivers/net/phy/phy_led_triggers.c
@@ -48,8 +48,9 @@ void phy_led_trigger_change_speed(struct phy_device *phy)
 		if (!phy->last_triggered)
 			led_trigger_event(&phy->led_link_trigger->trigger,
 					  LED_FULL);
+		else
+			led_trigger_event(&phy->last_triggered->trigger, LED_OFF);
 
-		led_trigger_event(&phy->last_triggered->trigger, LED_OFF);
 		led_trigger_event(&plt->trigger, LED_FULL);
 		phy->last_triggered = plt;
 	}
-- 
2.17.0

Re: [PATCH v2] net: phy: phy_led_triggers: Fix a possible null-pointer dereference in phy_led_trigger_change_speed()

[David Miller]

From: Jia-Ju Bai <baijiaju1990@gmail.com>
Date: Tue, 30 Jul 2019 16:08:13 +0800

> In phy_led_trigger_change_speed(), there is an if statement on line 48
> to check whether phy->last_triggered is NULL: 
>     if (!phy->last_triggered)
> 
> When phy->last_triggered is NULL, it is used on line 52:
>     led_trigger_event(&phy->last_triggered->trigger, LED_OFF);
> 
> Thus, a possible null-pointer dereference may occur.
> 
> To fix this bug, led_trigger_event(&phy->last_triggered->trigger,
> LED_OFF) is called when phy->last_triggered is not NULL.
> 
> This bug is found by a static analysis tool STCheck written by
> the OSLAB group in Tsinghua University.
> 
> Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>

Applied, thanks.