KVM: arm64: Fix debug checking for np-guests using huge mappings
CVE: CVE-2025-40184
Component: kernel
Severity: None
Release date: 2025-11-12T00:00:00+00:00

In the Linux kernel, the following vulnerability has been resolved:

KVM: arm64: Fix debug checking for np-guests using huge mappings

When running with transparent huge pages and CONFIG_NVHE_EL2_DEBUG then
the debug checking in assert_host_shared_guest() fails on the launch of an
np-guest. This WARN_ON() causes a panic and generates the stack below.

In __pkvm_host_relax_perms_guest() the debug checking assumes the mapping
is a single page but it may be a block map. Update the checking so that
the size is not checked and just assumes the correct size.

While we're here make the same fix in __pkvm_host_mkyoung_guest().

  Info: # lkvm run -k /share/arch/arm64/boot/Image -m 704 -c 8 --name guest-128
  Info: Removed ghost socket file "/.lkvm//guest-128.sock".
[ 1406.521757] kvm [141]: nVHE hyp BUG at: arch/arm64/kvm/hyp/nvhe/mem_protect.c:1088!
[ 1406.521804] kvm [141]: nVHE call trace:
[ 1406.521828] kvm [141]:  [<ffff8000811676b4>] __kvm_nvhe_hyp_panic+0xb4/0xe8
[ 1406.521946] kvm [141]:  [<ffff80008116d12c>] __kvm_nvhe_assert_host_shared_guest+0xb0/0x10c
[ 1406.522049] kvm [141]:  [<ffff80008116f068>] __kvm_nvhe___pkvm_host_relax_perms_guest+0x48/0x104
[ 1406.522157] kvm [141]:  [<ffff800081169df8>] __kvm_nvhe_handle___pkvm_host_relax_perms_guest+0x64/0x7c
[ 1406.522250] kvm [141]:  [<ffff800081169f0c>] __kvm_nvhe_handle_trap+0x8c/0x1a8
[ 1406.522333] kvm [141]:  [<ffff8000811680fc>] __kvm_nvhe___skip_pauth_save+0x4/0x4
[ 1406.522454] kvm [141]: ---[ end nVHE call trace ]---
[ 1406.522477] kvm [141]: Hyp Offset: 0xfffece8013600000
[ 1406.522554] Kernel panic - not syncing: HYP panic:
[ 1406.522554] PS:834003c9 PC:0000b1806db6d170 ESR:00000000f2000800
[ 1406.522554] FAR:ffff8000804be420 HPFAR:0000000000804be0 PAR:0000000000000000
[ 1406.522554] VCPU:0000000000000000
[ 1406.523337] CPU: 3 UID: 0 PID: 141 Comm: kvm-vcpu-0 Not tainted 6.16.0-rc7 #97 PREEMPT
[ 1406.523485] Hardware name: FVP Base RevC (DT)
[ 1406.523566] Call trace:
[ 1406.523629]  show_stack+0x18/0x24 (C)
[ 1406.523753]  dump_stack_lvl+0xd4/0x108
[ 1406.523899]  dump_stack+0x18/0x24
[ 1406.524040]  panic+0x3d8/0x448
[ 1406.524184]  nvhe_hyp_panic_handler+0x10c/0x23c
[ 1406.524325]  kvm_handle_guest_abort+0x68c/0x109c
[ 1406.524500]  handle_exit+0x60/0x17c
[ 1406.524630]  kvm_arch_vcpu_ioctl_run+0x2e0/0x8c0
[ 1406.524794]  kvm_vcpu_ioctl+0x1a8/0x9cc
[ 1406.524919]  __arm64_sys_ioctl+0xac/0x104
[ 1406.525067]  invoke_syscall+0x48/0x10c
[ 1406.525189]  el0_svc_common.constprop.0+0x40/0xe0
[ 1406.525322]  do_el0_svc+0x1c/0x28
[ 1406.525441]  el0_svc+0x38/0x120
[ 1406.525588]  el0t_64_sync_handler+0x10c/0x138
[ 1406.525750]  el0t_64_sync+0x1ac/0x1b0
[ 1406.525876] SMP: stopping secondary CPUs
[ 1406.525965] Kernel Offset: disabled
[ 1406.526032] CPU features: 0x0000,00000080,8e134ca1,9446773f
[ 1406.526130] Memory Limit: none
[ 1406.959099] ---[ end Kernel panic - not syncing: HYP panic:
[ 1406.959099] PS:834003c9 PC:0000b1806db6d170 ESR:00000000f2000800
[ 1406.959099] FAR:ffff8000804be420 HPFAR:0000000000804be0 PAR:0000000000000000
[ 1406.959099] VCPU:0000000000000000 ]


Remediation: