CVE-2024-56585: 
Linux Kernel vulnerability analysis and mitigation

CVE-2024-56585 affects the Linux kernel's LoongArch architecture implementation. The vulnerability was discovered in the TLB handler setup process where a sleeping function was called from an invalid context in PREEMPT_RT kernels. This issue was disclosed on December 27, 2024, and affects systems running Linux kernel with LoongArch architecture and PREEMPT_RT configuration (NVD).

The vulnerability occurs when the GFP flag is changed from GFP_KERNEL to GFP_ATOMIC for alloc_pages_node() in the setup_tlb_handler() function. In PREEMPT_RT kernels, normal spinlocks are replaced by rt spinlocks, and rt_spin_lock() causes sleeping in atomic context, triggering a BUG at kernel/locking/spinlock_rt.c:48. The issue manifests with multiple locks being held by the swapper process, including pcp->lock, rcu_read_lock, and zone->lock (Kernel Commit).

When triggered, this vulnerability causes a system bug that results in sleeping in atomic context, which can lead to system instability or crashes in affected LoongArch systems running with PREEMPT_RT kernel configuration (Kernel Commit).

The vulnerability is triggered during system initialization in specific hardware configurations running LoongArch architecture with PREEMPT_RT kernel configuration. It requires no special privileges to trigger as it occurs during normal system operation (NVD).

The issue has been fixed by disabling NUMA optimization completely for PREEMPT_RT kernels. The fix involves modifying the condition check in arch/loongarch/mm/tlb.c to include !defined(CONFIG_PREEMPT_RT) in the CONFIG_NUMA check (Kernel Commit).