kvm: arm/arm64: Fix use after free of stage2 page table

We yield the kvm->mmu_lock occassionaly while performing an operation
(e.g, unmap or permission changes) on a large area of stage2 mappings.
However this could possibly cause another thread to clear and free up
the stage2 page tables while we were waiting for regaining the lock and
thus the original thread could end up in accessing memory that was
freed. This patch fixes the problem by making sure that the stage2
pagetable is still valid after we regain the lock. The fact that
mmu_notifer->release() could be called twice (via __mmu_notifier_release
and mmu_notifier_unregsister) enhances the possibility of hitting
this race where there are two threads trying to unmap the entire guest
shadow pages.

While at it, cleanup the redudant checks around cond_resched_lock in
stage2_wp_range(), as cond_resched_lock already does the same checks.

Cc: Mark Rutland <[email protected]>
Cc: Radim Krčmář <[email protected]>
Cc: [email protected]
Cc: Paolo Bonzini <[email protected]>
Cc: [email protected]
Acked-by: Marc Zyngier <[email protected]>
Signed-off-by: Suzuki K Poulose <[email protected]>
Reviewed-by: Christoffer Dall <[email protected]>
Signed-off-by: Christoffer Dall <[email protected]>

0 files changed, 0 insertions, 0 deletions