From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751424AbeBHKYa (ORCPT ); Thu, 8 Feb 2018 05:24:30 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:57358 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750749AbeBHKY3 (ORCPT ); Thu, 8 Feb 2018 05:24:29 -0500 Subject: Re: [PATCH v2] KVM: X86: Fix SMRAM accessing even if VM is shutdown To: Wanpeng Li , linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= References: <1518075165-5376-1-git-send-email-wanpengli@tencent.com> From: Paolo Bonzini Message-ID: <75e8bfd0-6133-aabf-e1d0-d2e256d62994@redhat.com> Date: Thu, 8 Feb 2018 11:24:18 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.2 MIME-Version: 1.0 In-Reply-To: <1518075165-5376-1-git-send-email-wanpengli@tencent.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/02/2018 08:32, Wanpeng Li wrote: > From: Wanpeng Li > > Reported by syzkaller: > > WARNING: CPU: 6 PID: 2434 at arch/x86/kvm/vmx.c:6660 handle_ept_misconfig+0x54/0x1e0 [kvm_intel] > CPU: 6 PID: 2434 Comm: repro_test Not tainted 4.15.0+ #4 > RIP: 0010:handle_ept_misconfig+0x54/0x1e0 [kvm_intel] > Call Trace: > vmx_handle_exit+0xbd/0xe20 [kvm_intel] > kvm_arch_vcpu_ioctl_run+0xdaf/0x1d50 [kvm] > kvm_vcpu_ioctl+0x3e9/0x720 [kvm] > do_vfs_ioctl+0xa4/0x6a0 > SyS_ioctl+0x79/0x90 > entry_SYSCALL_64_fastpath+0x25/0x9c > > The syzkaller creates a former thread to issue KVM_SMI ioctl, and then creates > a latter thread to mmap and operate on the same vCPU, rsm emulation will not be > executed since there is no something like seabios which implements smi handler > when running syzkaller directly. This triggers a race condition when running > the testcase with multiple threads. Sometimes one thread exit w/ SHUTDOWN > reason, another thread mmaps and operates on the same vCPU, it continues to > use CS=0x30000, IP=0x8000 to access the address of SMI handler which results > in the above ept misconfig. This patch fixes it by returning RET_PF_EMULATE > in kvm_handle_bad_page() which would cause an emulation failure and then an > exit with KVM_EXIT_INTERNAL_ERROR, the VM will stop instead of resetting and > be taken advantage of. > > Reported-by: syzbot+c1d9517cab094dae65e446c0c5b4de6c40f4dc58@syzkaller.appspotmail.com > Cc: Paolo Bonzini > Cc: Radim Krčmář > Signed-off-by: Wanpeng Li > --- > v1 -> v2: > * return RET_PF_EMULATE > > arch/x86/kvm/mmu.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c > index 8eca1d0..6c5a82c 100644 > --- a/arch/x86/kvm/mmu.c > +++ b/arch/x86/kvm/mmu.c > @@ -3029,7 +3029,7 @@ static int kvm_handle_bad_page(struct kvm_vcpu *vcpu, gfn_t gfn, kvm_pfn_t pfn) > return RET_PF_RETRY; > } > > - return -EFAULT; > + return RET_PF_EMULATE; > } > > static void transparent_hugepage_adjust(struct kvm_vcpu *vcpu, > Reviewed-by: Paolo Bonzini