linux-cve-announce - CVE-2025-40184: KVM: arm64: Fix debug checking for np-guests using huge mappings

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Message-ID: <2025111243-CVE-2025-40184-9760@gregkh>
Date: Wed, 12 Nov 2025 17:00:47 -0500
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-40184: KVM: arm64: Fix debug checking for np-guests using huge mappings

From: Greg Kroah-Hartman <gregkh@...nel.org>

Description
===========

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 ]

The Linux kernel CVE team has assigned CVE-2025-40184 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.16 with commit f28f1d02f4eaac05c2ad6bf7264a8696dc21d011 and fixed in 6.17.4 with commit 4f7af3d8a1177c807d1f2563c7c171700b020656
	Issue introduced in 6.16 with commit f28f1d02f4eaac05c2ad6bf7264a8696dc21d011 and fixed in 6.18-rc1 with commit 2ba972bf71cb71d2127ec6c3db1ceb6dd0c73173

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2025-40184
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	arch/arm64/kvm/hyp/nvhe/mem_protect.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/4f7af3d8a1177c807d1f2563c7c171700b020656
	https://git.kernel.org/stable/c/2ba972bf71cb71d2127ec6c3db1ceb6dd0c73173