CVE-2024-26746 is a vulnerability identified in the Linux kernel's dmaengine idxd driver component. The issue arises specifically when the kernel is configured with CONFIG_HARDENED_USERCOPY enabled, a security feature designed to prevent unsafe copying of data between kernel and user space. The vulnerability is triggered during the copying of a completion record from the event log cache to user space. The root cause is that the event log cache is created using kmem_cache_create(), which is not designed to safely handle user copy operations. This improper cache creation leads to a kernel bug, evidenced by kernel memory exposure attempts and ultimately a kernel BUG triggered in the usercopy_abort function. The kernel panic and invalid opcode errors indicate a critical failure in memory safety checks. The fix involves changing the event log cache creation to use kmem_cache_create_usercopy(), which ensures that user copy operations are safely handled and memory exposure is prevented. This vulnerability could potentially be exploited to cause denial of service (kernel panic) or to leak kernel memory contents, depending on the attacker's ability to trigger the usercopy operation. However, exploitation requires the kernel to be built with CONFIG_HARDENED_USERCOPY enabled and the presence of the vulnerable idxd driver functionality. No known exploits are reported in the wild as of now.

For European organizations, this vulnerability poses a risk primarily to systems running Linux kernels with the CONFIG_HARDENED_USERCOPY option enabled and utilizing the dmaengine idxd driver, which is typically found on systems with Intel Data Streaming Accelerator (DSA) hardware. The impact includes potential denial of service due to kernel panics, which can disrupt critical services and infrastructure. Additionally, there is a risk of kernel memory exposure, which could lead to information disclosure of sensitive data residing in kernel memory. This is particularly concerning for data centers, cloud providers, and enterprises relying on Linux servers for critical workloads. The vulnerability could affect high-availability systems and those requiring strong security postures. Given the kernel panic and memory exposure risks, organizations may face operational disruptions and increased attack surface if threat actors develop exploits. However, the requirement for specific kernel configuration and hardware limits the scope somewhat. Still, the widespread use of Linux in European IT infrastructure means that many organizations could be affected if they run vulnerable kernel versions without patches.

European organizations should take the following specific steps beyond generic patching advice: 1) Identify Linux systems running kernels with CONFIG_HARDENED_USERCOPY enabled and verify if the dmaengine idxd driver is in use, especially on systems with Intel DSA hardware. 2) Apply the official Linux kernel patches that replace kmem_cache_create() with kmem_cache_create_usercopy() for the event log cache to ensure safe user copying. 3) Where patching is not immediately feasible, consider disabling the idxd driver or the CONFIG_HARDENED_USERCOPY kernel option temporarily if operationally acceptable, to mitigate risk. 4) Monitor kernel logs for usercopy abort messages or kernel BUG reports indicative of attempted exploitation. 5) Implement strict access controls to limit unprivileged user ability to trigger the vulnerable usercopy operations. 6) For cloud and virtualized environments, ensure hypervisor and host kernel versions are patched to prevent guest-to-host or host-to-guest attacks leveraging this vulnerability. 7) Conduct thorough testing of kernel updates in staging environments to avoid service disruptions. 8) Maintain up-to-date inventory of hardware and kernel configurations to rapidly identify vulnerable systems.