CVE-2024-56559: 
Linux Kernel vulnerability analysis and mitigation

CVE-2024-56559 addresses a performance issue in the Linux kernel related to TLB (Translation Lookaside Buffer) flush operations during KASAN (Kernel Address Sanitizer) shadow virtual address handling. The vulnerability was discovered when compiling kernel source with KASAN enabled on a 256-core machine, where it caused CPU soft lockups lasting up to 22 seconds (Kernel Git).

The issue manifests when the drain_vmap_area_work() function spends excessive time iterating vmap_nodes and flushing TLB when purging vm_area structures. Analysis showed approximately 2,805 flush_tlb_kernel_range() calls in the ftrace log, with each flush operation taking about 7.5ms, resulting in a total execution time of around 21.03 seconds. This prolonged execution triggers the soft lockup detector (Kernel Git).

The vulnerability causes significant performance degradation and system responsiveness issues on KASAN-enabled kernels, particularly on multi-core systems. When triggered, it results in CPU soft lockups that can last for over 22 seconds, potentially affecting system stability and performance (Kernel Git).

A temporary workaround involves extending the soft lockup timeout by modifying the watchdog threshold (echo 60 > /proc/sys/kernel/watchdog_thresh). The permanent fix combines all TLB flush operations of KASAN shadow virtual addresses into a single operation in the purge_vmap_node()->kasan_release_vmalloc() call path, reducing the drain_vmap_area_work() execution time to approximately 1 second (Kernel Git).