Description

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 any device tree overlays is unbinding the LED class device (pca9632@62) before unbinding the consumer (backlight-addon): echo 11-0062 >/sys/bus/i2c/drivers/leds-pca963x/unbind echo ...backlight-dock >/sys/bus/platform/drivers/led-backlight/unbind Fix by adding a devlink between the consuming led-backlight device and the supplying LED device, as other drivers and subsystems do as well.

References 8

• git.kernel.org https://git.kernel.org/stable/c/08c9dc6b0f2c68e5e7c374ac4499e321e435d46c
• git.kernel.org https://git.kernel.org/stable/c/0e63ea4378489e09eb5e920c8a50c10caacf563a
• git.kernel.org https://git.kernel.org/stable/c/30cbe4b642745a9488a0f0d78be43afe69d7555c
• git.kernel.org https://git.kernel.org/stable/c/60a24070392ec726ccfe6ad1ca7b0381c8d8f7c9
• git.kernel.org https://git.kernel.org/stable/c/64739adf3eef063b8e2c72b7e919eac8c6480bf0
• git.kernel.org https://git.kernel.org/stable/c/9341d6698f4cfdfc374fb6944158d111ebe16a9d
• git.kernel.org https://git.kernel.org/stable/c/cd01a24b3e52d6777b49c917d841f125fe9eebd0
• git.kernel.org https://git.kernel.org/stable/c/e06df738a9ad8417f1c4c7cd6992cda320e9e7ca

Remediation