Medium · published September 16, 2025
In the Linux kernel, the following vulnerability has been resolved:
KVM: arm64: Handle kvm_arm_init failure correctly in finalize_pkvm
Currently there is no synchronisation between finalize_pkvm() and
kvm_arm_init() initcalls. The finalize_pkvm() proceeds happily even if
kvm_arm_init() fails resulting in the following warning on all the CPUs
and eventually a HYP panic:
| kvm [1]: IPA Size Limit: 48 bits
| kvm [1]: Failed to init hyp memory protection
| kvm [1]: error initializing Hyp mode: -22
|
| <snip>
|
| WARNING: CPU: 0 PID: 0 at arch/arm64/kvm/pkvm.c:226 _kvm_host_prot_finalize+0x30/0x50
| Modules linked in:
| CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.4.0 #237
| Hardware name: FVP Base RevC (DT)
| pstate: 634020c5 (nZCv daIF +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
| pc : _kvm_host_prot_finalize+0x30/0x50
| lr : __flush_smp_call_function_queue+0xd8/0x230
|
| Call trace:
| _kvm_host_prot_finalize+0x3c/0x50
| on_each_cpu_cond_mask+0x3c/0x6c
| pkvm_drop_host_privileges+0x4c/0x78
| finalize_pkvm+0x3c/0x5c
| do_one_initcall+0xcc/0x240
| do_initcall_level+0x8c/0xac
| do_initcalls+0x54/0x94
| do_basic_setup+0x1c/0x28
| kernel_init_freeable+0x100/0x16c
| kernel_init+0x20/0x1a0
| ret_from_fork+0x10/0x20
| Failed to finalize Hyp protection: -22
| dtb=fvp-base-revc.dtb
| kvm [95]: nVHE hyp BUG at: arch/arm64/kvm/hyp/nvhe/mem_protect.c:540!
| kvm [95]: nVHE call trace:
| kvm [95]: [<ffff800081052984>] __kvm_nvhe_hyp_panic+0xac/0xf8
| kvm [95]: [<ffff800081059644>] __kvm_nvhe_handle_host_mem_abort+0x1a0/0x2ac
| kvm [95]: [<ffff80008105511c>] __kvm_nvhe_handle_trap+0x4c/0x160
| kvm [95]: [<ffff8000810540fc>] __kvm_nvhe___skip_pauth_save+0x4/0x4
| kvm [95]: ---[ end nVHE call trace ]---
| kvm [95]: Hyp Offset: 0xfffe8db00ffa0000
| Kernel panic - not syncing: HYP panic:
| PS:a34023c9 PC:0000f250710b973c ESR:00000000f2000800
| FAR:ffff000800cb00d0 HPFAR:000000000880cb00 PAR:0000000000000000
| VCPU:0000000000000000
| CPU: 3 PID: 95 Comm: kworker/u16:2 Tainted: G W 6.4.0 #237
| Hardware name: FVP Base RevC (DT)
| Workqueue: rpciod rpc_async_schedule
| Call trace:
| dump_backtrace+0xec/0x108
| show_stack+0x18/0x2c
| dump_stack_lvl+0x50/0x68
| dump_stack+0x18/0x24
| panic+0x138/0x33c
| nvhe_hyp_panic_handler+0x100/0x184
| new_slab+0x23c/0x54c
| ___slab_alloc+0x3e4/0x770
| kmem_cache_alloc_node+0x1f0/0x278
| __alloc_skb+0xdc/0x294
| tcp_stream_alloc_skb+0x2c/0xf0
| tcp_sendmsg_locked+0x3d0/0xda4
| tcp_sendmsg+0x38/0x5c
| inet_sendmsg+0x44/0x60
| sock_sendmsg+0x1c/0x34
| xprt_sock_sendmsg+0xdc/0x274
| xs_tcp_send_request+0x1ac/0x28c
| xprt_transmit+0xcc/0x300
| call_transmit+0x78/0x90
| __rpc_execute+0x114/0x3d8
| rpc_async_schedule+0x28/0x48
| process_one_work+0x1d8/0x314
| worker_thread+0x248/0x474
| kthread+0xfc/0x184
| ret_from_fork+0x10/0x20
| SMP: stopping secondary CPUs
| Kernel Offset: 0x57c5cb460000 from 0xffff800080000000
| PHYS_OFFSET: 0x80000000
| CPU features: 0x00000000,1035b7a3,ccfe773f
| Memory Limit: none
| ---[ end Kernel panic - not syncing: HYP panic:
| PS:a34023c9 PC:0000f250710b973c ESR:00000000f2000800
| FAR:ffff000800cb00d0 HPFAR:000000000880cb00 PAR:0000000000000000
| VCPU:0000000000000000 ]---
Fix it by checking for the successfull initialisation of kvm_arm_init()
in finalize_pkvm() before proceeding any futher.