In the Linux kernel, the following vulnerability has been resolved: rpmsg: core: fix race in driver_override_show() and use core helper The driver_override_show function reads the driver_override string without holding the device_lock.…

Overview

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

rpmsg: core: fix race in driver_override_show() and use core helper

The driver_override_show function reads the driver_override string without holding the device_lock. However, the store function modifies and frees the string while holding the device_lock. This creates a race condition where the string can be freed by the store function while being read by the show function, leading to a use-after-free.

To fix this, replace the rpmsg_string_attr macro with explicit show and store functions. The new driver_override_store uses the standard driver_set_override helper. Since the introduction of driver_set_override, the comments in include/linux/rpmsg.h have stated that this helper must be used to set or clear driver_override, but the implementation was not updated until now.

Because driver_set_override modifies and frees the string while holding the device_lock, the new driver_override_show now correctly holds the device_lock during the read operation to prevent the race.

Additionally, since rpmsg_string_attr has only ever been used for driver_override, removing the macro simplifies the code.

Affected

• linux_kernel >= 4.18, < 5.10.252
• linux_kernel >= 5.11, < 5.15.202
• linux_kernel >= 5.16, < 6.1.165
• linux_kernel >= 6.2, < 6.6.128
• linux_kernel >= 6.7, < 6.12.75
• linux_kernel >= 6.13, < 6.18.16
• linux_kernel >= 6.19, < 6.19.6

Remediation

Upgrade past the affected range:

• linux_kernel 6.19.6