KVM: arm64: Add fail-safe for refcounted pages in __pkvm_hyp_donate_host

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A previous bug in __pkvm_init_vm error path showed that the hypervisor
could leak refcounted pages, (i.e. losing access to a page while its
refcount is still elevated). This poses a threat to the pKVM state
machine.

Address this by introducing a fail-safe in __pkvm_hyp_donate_host.
Transitions are not a hot path so added security is worth the extra
check.

Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Link: https://patch.msgid.link/20260521143626.1005660-4-vdonnefort@google.com
Signed-off-by: Marc Zyngier <maz@kernel.org>

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Vincent Donnefort 2026-05-21 15:36:26 +01:00 • committed by Marc Zyngier

parent 20d2753295

commit 5c30c9fc11

1 changed files with 16 additions and 4 deletions

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arch/arm64/kvm/hyp/nvhe/mem_protect.c

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