[PATCH 1/2] KVM: arm64: Don't leave mmu->pgt dangling on kvm_init_stage2_mmu() error

[Will Deacon]

If kvm_init_stage2_mmu() fails to allocate 'mmu->last_vcpu_ran', it
destroys the newly allocated stage-2 page-table before returning ENOMEM.

Unfortunately, it also leaves a dangling pointer in 'mmu->pgt' which
points at the freed 'kvm_pgtable' structure. This is likely to confuse
the kvm_vcpu_init_nested() failure path which can double-free the
structure if it finds it via kvm_free_stage2_pgd().

Ensure that the dangling 'mmu->pgt' pointer is cleared when returning an
error from kvm_init_stage2_mmu().

Link: https://sashiko.dev/#/patchset/20260327140039.21228-1-will%40kernel.org?patch=12265
Signed-off-by: Will Deacon <will at kernel.org>
---
 arch/arm64/kvm/mmu.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 17d64a1e11e5..34e9d897d08b 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1013,6 +1013,7 @@ int kvm_init_stage2_mmu(struct kvm *kvm, struct kvm_s2_mmu *mmu, unsigned long t
 
 out_destroy_pgtable:
 	kvm_stage2_destroy(pgt);
+	mmu->pgt = NULL;
 out_free_pgtable:
 	kfree(pgt);
 	return err;
-- 
2.53.0.1018.g2bb0e51243-goog