CVE-2025-40184
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-11-12

Last updated on: 2025-11-14

Assigner: kernel.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 ]
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Meta Information
Published
2025-11-12
Last Modified
2025-11-14
Generated
2026-05-07
AI Q&A
2025-11-13
EPSS Evaluated
2026-05-05
NVD
CVE-2025-40184
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel 6.16.0-rc7
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-UNKNOWN
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability occurs in the Linux kernel's KVM module for arm64 architecture. When running with transparent huge pages and a specific debug configuration (CONFIG_NVHE_EL2_DEBUG), the debug checking in the function assert_host_shared_guest() fails during the launch of a non-primary (np) guest virtual machine. This failure triggers a WARN_ON() which causes a kernel panic. The root cause is that the debug checking incorrectly assumes memory mappings are single pages, but they may be block mappings (huge pages). The fix updates the debug checking to not verify the size and assume the correct size instead, preventing the panic.


How can this vulnerability impact me? :

This vulnerability can cause a kernel panic when launching np-guests under certain configurations, leading to system crashes and downtime. This can disrupt services running on affected systems, potentially causing loss of availability and requiring system reboots to recover.


How can this vulnerability be detected on my network or system? Can you suggest some commands?

This vulnerability can be detected by monitoring the system logs for kernel panic messages related to KVM on arm64 with transparent huge pages and CONFIG_NVHE_EL2_DEBUG enabled. Specifically, look for WARN_ON() panics with messages similar to 'nVHE hyp BUG' and call traces involving __kvm_nvhe_assert_host_shared_guest() and __pkvm_host_relax_perms_guest(). Checking dmesg or journalctl logs for these kernel panic traces can help identify the issue. Example commands to check logs include: 'dmesg | grep -i kvm' or 'journalctl -k | grep -i kvm'.


What immediate steps should I take to mitigate this vulnerability?

Immediate mitigation involves updating the Linux kernel to a version where this vulnerability is fixed, as the issue is resolved by correcting debug checking in the kernel code for np-guests using huge mappings. Until an update is applied, avoid running np-guests with transparent huge pages enabled and CONFIG_NVHE_EL2_DEBUG active, as these conditions trigger the panic. Monitoring for kernel panics and avoiding configurations that trigger the bug are recommended interim steps.


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