From 5b73d6347eb82cd2a26698fc339607e25e0ad917 Mon Sep 17 00:00:00 2001 From: David Gibson Date: Wed, 15 Feb 2017 14:40:04 +1100 Subject: [PATCH] KVM: PPC: Book3S HV: Prevent double-free on HPT resize commit path resize_hpt_release(), called once the HPT resize of a KVM guest is completed (successfully or unsuccessfully) frees the state structure for the resize. It is currently not safe to call with a NULL pointer. However, one of the error paths in kvm_vm_ioctl_resize_hpt_commit() can invoke it with a NULL pointer. This will occur if userspace improperly invokes KVM_PPC_RESIZE_HPT_COMMIT without previously calling KVM_PPC_RESIZE_HPT_PREPARE, or if it calls COMMIT twice without an intervening PREPARE. To fix this potential crash bug - and maybe others like it, make it safe (and a no-op) to call resize_hpt_release() with a NULL resize pointer. Found by Dan Carpenter with a static checker. Reported-by: Dan Carpenter Signed-off-by: David Gibson Signed-off-by: Paul Mackerras --- arch/powerpc/kvm/book3s_64_mmu_hv.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c index 013552f05182..72ccac26e464 100644 --- a/arch/powerpc/kvm/book3s_64_mmu_hv.c +++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c @@ -1407,6 +1407,9 @@ static void resize_hpt_release(struct kvm *kvm, struct kvm_resize_hpt *resize) { BUG_ON(kvm->arch.resize_hpt != resize); + if (!resize) + return; + if (resize->hpt.virt) kvmppc_free_hpt(&resize->hpt); -- 2.20.1