CVE-2024-50303 is a vulnerability identified in the Linux kernel related to the handling of system RAM resources during the kexec process. Specifically, the function walk_system_ram_res_rev() erroneously discards resource flags when passing memory resource information to its callback. This flaw affects systems that have IORESOURCE_SYSRAM_DRIVER_MANAGED memory regions, particularly when such memory is located above the normal system RAM address range. The improper handling causes these memory resources to be mistakenly selected for storing kexec buffers. Kexec is a mechanism that allows loading and booting into a new kernel without going through a full hardware reboot. The consequence of this mismanagement is undefined behavior after a kexec reboot. If the kexec buffer is never accessed, the system may appear unaffected. However, if the buffer is accessed, it can lead to kernel crashes or other unpredictable behavior. The vulnerability was tested on systems with CXL memory expanders (which provide additional driver-managed memory), TPM enabled, and the kernel configured with IMA kexec support (CONFIG_IMA_KEXEC=y). Kernel logs demonstrate that resource flags are lost, causing the system to treat driver-managed memory as normal system RAM, leading to page faults and kernel oops errors during the IMA measurement list restoration phase after reboot. This vulnerability is subtle and specific to advanced memory configurations involving driver-managed system RAM and kexec. It can cause system instability or crashes post-kexec reboot, impacting system availability. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet. The issue is primarily a kernel memory management bug affecting Linux kernel versions identified by the given commit hashes.

For European organizations, the impact of CVE-2024-50303 depends on their use of Linux systems with advanced memory configurations such as CXL memory expanders and TPM, and whether they utilize kexec for kernel reboots. Organizations relying on kexec for fast kernel switching or system recovery could face unexpected system crashes or undefined behavior after reboot, potentially leading to downtime or service interruptions. This is particularly critical for data centers, cloud providers, and enterprises running high-availability Linux servers with these configurations. The vulnerability affects system availability primarily, as kernel crashes can cause service outages. Confidentiality and integrity impacts are less direct but could arise if system instability leads to failures in security modules like IMA (Integrity Measurement Architecture). Systems with TPM and IMA enabled may experience failures in security measurement restoration, potentially weakening trust in system integrity post-reboot. Given the complexity of the affected configurations, the threat is more relevant to organizations with cutting-edge hardware deployments or specialized Linux kernel setups rather than typical desktop or server environments. However, critical infrastructure or research institutions using such configurations in Europe could be at risk of operational disruption.

1. Apply the official Linux kernel patches that address this issue as soon as they become available. Monitor Linux kernel mailing lists and vendor advisories for updates related to CVE-2024-50303. 2. Until patches are applied, avoid using kexec on systems with IORESOURCE_SYSRAM_DRIVER_MANAGED memory regions, especially those with CXL memory expanders and TPM enabled. 3. Review system configurations to identify the presence of driver-managed system RAM and evaluate the necessity of kexec usage in these environments. 4. Implement rigorous testing of kernel updates and kexec operations in controlled environments before deploying to production systems. 5. Monitor kernel logs for page faults or oops messages related to ima_restore_measurement_list or kexec buffer handling, which may indicate exploitation or manifestation of this vulnerability. 6. Coordinate with hardware vendors to understand the deployment of CXL memory expanders and ensure firmware and drivers are up to date to minimize related risks. 7. For critical systems, consider fallback mechanisms or redundant systems to maintain availability in case of crashes triggered by this vulnerability.