CVE-2026-80726: KVM: x86/mmu: WARN and clear role.invalid when creating a child shadow page
In the Linux kernel, the following vulnerability has been resolved:
KVM: x86/mmu: WARN and clear role.invalid when creating a child shadow page
Explicitly clear role.invalid when deriving a child shadow page's role from its parent to harden against bugs elsewhere in KVM, as violating KVM's invariant that invalid pages are NOT on the list of active MMU pages leads to use-after-free due to kvmmmupreparezappage() using listadd() instead of listmove() when processing an invalid shadow page, i.e. makes a bad situation far worse.
Yell loudly if the parent is invalid, as it means KVM has missed a validity check, i.e. KVM is attempting to map memory using an invalid/obsolete root, but continue on as the child is otherwise still a valid shadow page.
================================================================== BUG: KASAN: slab-use-after-free in kvmmmugetshadowpage+0x1817/0x1860 [kvm] Write of size 8 at addr ff11000153dd1368 by task repro/853
CPU: 1 UID: 1000 PID: 853 Comm: repro Not tainted 7.2.0-rc2-3aec122bdcaf-next-vm #5 PREEMPT Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 Call Trace: <TASK> dumpstacklvl+0x4b/0x70 printreport+0x153/0x49c kasanreport+0xbc/0xf0 kvmmmugetshadowpage+0x1817/0x1860 [kvm] mmuallocroot+0x141/0x320 [kvm] kvmmmuload+0x612/0x20f0 [kvm] kvmarchvcpuioctlrun+0x3dd5/0x6150 [kvm] kvmvcpuioctl+0x5e4/0x10d0 [kvm] x64sysioctl+0x131/0x1b0 dosyscall64+0x67/0x5f0 entrySYSCALL64afterhwframe+0x4b/0x53 </TASK>
Allocated by task 853: kasansavestack+0x20/0x40 kasansavetrack+0x14/0x30 kasanslaballoc+0x5f/0x70 kmemcacheallocnoprof+0xfe/0x2e0 kvmmmutopupmemorycache+0x135/0x530 [kvm] paging64pagefault+0x318/0x1e30 [kvm] kvmmmudopagefault+0x21d/0x630 [kvm] kvmmmupagefault+0x18c/0x17b0 [kvm] kvmarchvcpuioctlrun+0x1f35/0x6150 [kvm] kvmvcpuioctl+0x5e4/0x10d0 [kvm] x64sysioctl+0x131/0x1b0 dosyscall64+0x67/0x5f0 entrySYSCALL64afterhwframe+0x4b/0x53
Freed by task 853: kasansavestack+0x20/0x40 kasansavetrack+0x14/0x30 kasansavefreeinfo+0x3b/0x60 kasanslabfree+0x43/0x70 kmemcachefree+0xe2/0x400 kvmmmucommitzappage.part.0+0x1e2/0x310 [kvm] kvmmmufreeroots+0x283/0x560 [kvm] kvmarchvcpuioctlrun+0x33c8/0x6150 [kvm] kvmvcpuioctl+0x5e4/0x10d0 [kvm] x64sysioctl+0x131/0x1b0 dosyscall64+0x67/0x5f0 entrySYSCALL64afterhwframe+0x4b/0x53
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Linux kernel (KVM)to a version that resolves this vulnerability.Fixed in 7.2.0-rc2-3aec122bdcaf-next-vm #5 PREEMPTPatch KVM: x86/mmu: WARN and clear role.invalid when creating a child shadow page
Event History
Frequently Asked Questions
Which systems are in scope?
The issue is in the Linux kernel's KVM x86 MMU code. Systems that do not use KVM's x86 memory-management functionality are not the component described here.
What should operators look for when investigating whether this condition has occurred?
KVM emits a warning if it attempts to create a child shadow page from an invalid parent. That warning indicates KVM is attempting to map memory using an invalid or obsolete root and has missed a validity check.
What is the observed failure mode?
The reported failure is a KASAN-detected slab use-after-free in the KVM module, specifically in __kvm_mmu_get_shadow_page. The underlying condition involves an invalid shadow page being present on the active MMU page list.
Are fixes identified in the available data?
Yes. The references identify stable-tree commits 9b7984692c18b22d6d61af3f53887fca7fddb0f1, f33ecb89d352348ed5e625f6747ac51ede254e1b, and 0af4711862c5b818204d40b21f0859ad51c230e9. No affected or fixed kernel version ranges are provided.