CVE-2023-53319: KVM: arm64: Handle kvm_arm_init failure correctly in finalize_pkvm
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.
CVSS v3.1: 5.5