CVE-2024-50303: 
Linux Kernel vulnerability analysis and mitigation

In the Linux kernel, a vulnerability (CVE-2024-50303) was discovered in the walk_system_ram_res_rev() function. The function erroneously discards resource flags when passing information to the callback. This affects systems with IORESOURCE_SYSRAM_DRIVER_MANAGED memory, particularly when these resources are selected during kexec to store kexec buffers if that memory is placed above normal system RAM (Kernel Patch).

The vulnerability stems from the walk_system_ram_res_rev() function's handling of resource flags. When the function processes memory resources, it fails to retain the resource flags during the callback operation. This specifically impacts systems where IORESOURCE_SYSRAM_DRIVER_MANAGED memory is present and positioned above normal system RAM. The issue has been assigned a CVSS v3.1 base score of 5.5 (Medium) with vector string CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H (NVD).

The vulnerability leads to undefined behavior after reboot. If the kexec buffer is never accessed, there are no immediate consequences. However, if the kexec buffer is touched, it can result in system crashes or undefined behavior. This has been confirmed on systems with CXL memory expanders with driver managed memory, TPM enabled, and CONFIG_IMA_KEXEC=y (Kernel Patch).

The vulnerability requires local access to the system and can be triggered when specific conditions are met, including the presence of IORESOURCE_SYSRAM_DRIVER_MANAGED memory and its placement above normal system RAM. The issue manifests during the kexec process, particularly when accessing affected memory regions (NVD).

The vulnerability has been fixed in the Linux kernel through a patch that ensures resource flags are properly retained in the walk_system_ram_res_rev() function. The fix involves modifying how the function handles resource information passing to the callback. Users should update to kernel versions that include this fix (Kernel Patch).