CVE-2026-53359

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

KVM: x86: Fix shadow paging use-after-free due to unexpected role

Commit 0cb2af2ea66ad ("KVM: x86: Fix shadow paging use-after-free due

to unexpected GFN") fixed a shadow paging mismatch between stored and

computed GFNs; the bug could be triggered by changing a PDE mapping from

outside the guest, and then deleting a memslot. The rmap_remove()

call would miss entries created after the PDE change because the GFN

of the leaf SPTE does not match the GFN of the struct kvm_mmu_page.

A similar hole however remains if the modified PDE points to a non-leaf

page. In this case the gfn can be made to match, but the role does not

match: the original large 2MB page creates a kvm_mmu_page with direct=1,

while the new 4KB needs a kvm_mmu_page with direct=0. However,

kvm_mmu_get_child_sp() does not compare the role, and therefore reuses

the page.

The next step is installing a leaf (4KB) SPTE on the new path which

records an rmap entry under the gfn resolved by the walk. But when

that child is zapped its parent kvm_mmu_page has direct=1 and

kvm_mmu_page_get_gfn() computes the gfn for the 4KB page as

sp->gfn + index instead of using sp->shadowed_translation[] (or sp->gfns[]

in older kernels). It therefore fails to remove the recorded entry.

When the memslot is dropped the shadow page is freed but the rmap

entry survives, as in the scenario that was already fixed. Code that

later walks that gfn (dirty logging, MMU notifier invalidation, and

so on) dereferences an sptep that lies in the freed page, causing the

use-after-free.