Linux Kernel CAN Interface Out-of-Bounds Read Vulnerability Leading to Frame Drops

A vulnerability in the Linux kernel's CAN subsystem can cause virtual CAN interfaces, such as vcan and vxcan, to drop CAN frames. This issue arises from an out-of-bounds read related to the 'priv->ctrlmode' element, which is accessed even on virtual CAN interfaces that do not initialize the 'can_priv' structure at startup. The problem was introduced in a previous commit and has been addressed by reverting that change and implementing a new helper for CAN interface drivers to provide the necessary information.

Impact

Exploitation of this vulnerability can lead to unintended drops of CAN frames on affected virtual CAN interfaces.