CVE-2024-26846: 
Linux Kernel vulnerability analysis and mitigation

CVE-2024-26846 affects the Linux kernel's NVMe over Fibre Channel (nvme-fc) module. The vulnerability was discovered in the module exit path where there exists a race condition between deleting all controllers and freeing 'left over IDs'. This issue was identified and fixed in January 2024 (Kernel Git).

The vulnerability stems from a synchronization issue in the nvme-fc module's exit path. The original code attempted to prevent double-free conditions by adding synchronization between nvme_delete_ctrl and ida_destroy. However, the implementation contained logic that could lead to an infinite hang in wait_for_completion, which was reproducible through blktests (Kernel Git). The CVSS 3.1 base score for this vulnerability is 4.4 (MEDIUM) with vector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H (NVD).

The vulnerability can result in a system hang during module unload operations, potentially causing a denial of service condition. The issue specifically affects systems using the NVMe over Fibre Channel module (NVD).

The vulnerability requires local access with high privileges to exploit, as it involves module unload operations. The issue is specifically triggered during the cleanup process when unloading the nvme-fc module (NVD).

The issue has been fixed by modifying the cleanup code to rely completely on the nvme_delete_ctrl path for freeing IDs and removing the unnecessary ida_destroy calls. The fix ensures proper execution of all nvme_delete_ctrl code before leaving nvme_fc_exit_module by flushing the nvme_delete_wq workqueue (Kernel Git).