CVE-2026-68428

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

KVM: x86/mmu: Fix use-after-free on vendor module reload

mmu_destroy_caches() destroys pte_list_desc_cache and

mmu_page_header_cache, but leaves both pointers unchanged. The pointers

live in kvm.ko, and therefore survive when a vendor module is unloaded

while kvm.ko remains loaded.

If creation of pte_list_desc_cache fails during a subsequent vendor

module load, its assignment sets pte_list_desc_cache to NULL and the

error path calls mmu_destroy_caches(). mmu_page_header_cache still

points to the cache destroyed during the preceding vendor module

unload. Passing that stale pointer to kmem_cache_destroy() causes a

slab use-after-free.

Reproduce the issue on a v7.1.3 kernel with CONFIG_KASAN=y,

CONFIG_KASAN_GENERIC=y, CONFIG_KVM=m, and CONFIG_KVM_INTEL=m. A

one-shot test hook forces pte_list_desc_cache to NULL on the second

invocation of kvm_mmu_vendor_module_init():

1. Load kvm.ko and kvm-intel.ko, creating both caches.

2. Unload only kvm_intel, leaving kvm.ko loaded.

3. Reload kvm_intel and force initialization through the -ENOMEM path.

KASAN reports:

BUG: KASAN: slab-use-after-free in

kvm_mmu_vendor_module_init+0x5b/0x170 [kvm]

...

kmem_cache_destroy+0x21/0x1d0

kvm_mmu_vendor_module_init+0x5b/0x170 [kvm]

...

Allocated by task 16817:

__kmem_cache_create_args+0x12c/0x3b0

__kmem_cache_create.constprop.0+0xb6/0xf0 [kvm]

kvm_mmu_vendor_module_init+0x13b/0x170 [kvm]

...

Freed by task 16820:

kmem_cache_destroy+0x117/0x1d0

kvm_mmu_vendor_module_exit+0x21/0x30 [kvm]

Clear both pointers immediately after destroying their caches so that

the stored state reflects the caches' lifetime and repeated cleanup is

safe.

With the fix applied, the same injected vendor module reload fails with

-ENOMEM as expected and produces no KASAN report.