From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (ozlabs.org [IPv6:2401:3900:2:1::2]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3vNQ621TCFzDq5W for ; Wed, 15 Feb 2017 14:40:10 +1100 (AEDT) From: David Gibson To: paulus@samba.org Cc: dan.carpenter@oracle.com, linuxppc-dev@lists.ozlabs.org, kvm-ppc@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, David Gibson Subject: [PATCH] KVM: Prevent double-free on HPT resize commit path Date: Wed, 15 Feb 2017 14:40:04 +1100 Message-Id: <20170215034004.9255-1-david@gibson.dropbear.id.au> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , resize_hpt_release(), called once the HPT resize of a KVM guest is completed (successfully or unsuccessfully) free()s 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 --- 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 013552f..72ccac2 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); -- 2.9.3