Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

backlight: led-bl: Add devlink to supplier LEDs

LED Backlight is a consumer of one or multiple LED class devices, but devlink is currently unable to create correct supplier-producer links when the supplier is a class device. It creates instead a link where the supplier is the parent of the expected device.

One consequence is that removal order is not correctly enforced.

Issues happen for example with the following sections in a device tree overlay:

// An LED driver chip pca9632@62 { compatible = "nxp,pca9632"; reg = <0x62>;

// ...

addon_led_pwm: led-pwm@3 { reg = <3>; label = "addon:led:pwm"; }; };

backlight-addon { compatible = "led-backlight"; leds = <&addon_led_pwm>; brightness-levels = <255>; default-brightness-level = <255>; };

In this example, the devlink should be created between the backlight-addon (consumer) and the pca9632@62 (supplier). Instead it is created between the backlight-addon (consumer) and the parent of the pca9632@62, which is typically the I2C bus adapter.

On removal of the above overlay, the LED driver can be removed before the backlight device, resulting in:

Unable to handle kernel NULL pointer dereference at virtual address 0000000000000010 ... Call trace: led_put+0xe0/0x140 devm_led_release+0x6c/0x98

Another way to reproduce the bug without…