CVE-2022-49220: 
Linux Kernel vulnerability analysis and mitigation

CVE-2022-49220 affects the Linux kernel's DAX (Direct Access) filesystem module. The vulnerability was discovered when a bug could be triggered by executing the command sequence 'modprobe nd_pmem && modprobe -r nd_pmem', which resulted in objects remaining in dax_cache during __kmem_cache_shutdown(). This issue was caused by dax_fs_exit() not properly flushing inodes before destroying the cache (NVD).

The vulnerability occurs in the Linux kernel's DAX module, specifically in the dax_fs_exit() function within the drivers/dax/super.c file. When unloading the nd_pmem module, the system encounters a BUG condition in dax_cache with objects remaining during cache shutdown. The issue manifests with a slab containing objects=9 and used=1, indicating improper cleanup of cache objects (Kernel Commit).

When triggered, the vulnerability causes a kernel bug condition that could potentially lead to system instability. The bug manifests when attempting to remove the nd_pmem module, leaving residual objects in the dax_cache during shutdown operations (NVD).

The vulnerability can be triggered through a specific sequence of module loading and unloading operations using the nd_pmem module. The exploit path requires local access to the system and the ability to load and unload kernel modules (Kernel Commit).

The issue has been fixed by adding an rcu_barrier() call before destroying the cache in the dax_fs_exit() function. This ensures that all inodes are properly flushed before the cache is destroyed. The fix was implemented in the Linux kernel through a patch that addresses the root cause of the issue (Kernel Commit).