Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752707AbdLNOSv (ORCPT ); Thu, 14 Dec 2017 09:18:51 -0500 Received: from aserp2120.oracle.com ([141.146.126.78]:53416 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752580AbdLNOSs (ORCPT ); Thu, 14 Dec 2017 09:18:48 -0500 Date: Thu, 14 Dec 2017 14:18:36 +0000 From: Darren Kenny To: Wanpeng Li Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Paolo Bonzini , Radim =?utf-8?B?S3LEjW3DocWZ?= , Wanpeng Li Subject: Re: [PATCH v3] KVM: X86: Fix stack-out-of-bounds read in write_mmio Message-ID: <20171214141836.7ndd6i3qaef36e2o@starbug-vm.ie.oracle.com> Mail-Followup-To: Wanpeng Li , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Paolo Bonzini , Radim =?utf-8?B?S3LEjW3DocWZ?= , Wanpeng Li References: <1513259818-11419-1-git-send-email-wanpeng.li@hotmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1513259818-11419-1-git-send-email-wanpeng.li@hotmail.com> User-Agent: NeoMutt/20171027 X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=8744 signatures=668646 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1711220000 definitions=main-1712140195 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4805 Lines: 141 Hi, I'm wondering about the change to trace_kvm_mmio() here, since it doesn't appear to be changing the use of it in virt/kvm/arm/mmio.c, e.g: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/virt/kvm/arm/mmio.c#n114 which seems to be still using it with a data value rather than a pointer like you've changed it to in the header. Should that also be modified to match? As it is, it would appear to cause a compilation error on ARM (though I've not confirmed). Thanks, Darren. On Thu, Dec 14, 2017 at 05:56:58AM -0800, Wanpeng Li wrote: >From: Wanpeng Li > >Reported by syzkaller: > > BUG: KASAN: stack-out-of-bounds in write_mmio+0x11e/0x270 [kvm] > Read of size 8 at addr ffff8803259df7f8 by task syz-executor/32298 > > CPU: 6 PID: 32298 Comm: syz-executor Tainted: G OE 4.15.0-rc2+ #18 > Hardware name: LENOVO ThinkCentre M8500t-N000/SHARKBAY, BIOS FBKTC1AUS 02/16/2016 > Call Trace: > dump_stack+0xab/0xe1 > print_address_description+0x6b/0x290 > kasan_report+0x28a/0x370 > write_mmio+0x11e/0x270 [kvm] > emulator_read_write_onepage+0x311/0x600 [kvm] > emulator_read_write+0xef/0x240 [kvm] > emulator_fix_hypercall+0x105/0x150 [kvm] > em_hypercall+0x2b/0x80 [kvm] > x86_emulate_insn+0x2b1/0x1640 [kvm] > x86_emulate_instruction+0x39a/0xb90 [kvm] > handle_exception+0x1b4/0x4d0 [kvm_intel] > vcpu_enter_guest+0x15a0/0x2640 [kvm] > kvm_arch_vcpu_ioctl_run+0x549/0x7d0 [kvm] > kvm_vcpu_ioctl+0x479/0x880 [kvm] > do_vfs_ioctl+0x142/0x9a0 > SyS_ioctl+0x74/0x80 > entry_SYSCALL_64_fastpath+0x23/0x9a > >The path of patched vmmcall will patch 3 bytes opcode 0F 01 C1(vmcall) >to the guest memory, however, write_mmio tracepoint always prints 8 bytes >through *(u64 *)val since kvm splits the mmio access into 8 bytes. This >can result in stack-out-of-bounds read due to access the extra 5 bytes. >This patch fixes it by just accessing the bytes which we operates on. > >Before patch: > >syz-executor-5567 [007] .... 51370.561696: kvm_mmio: mmio write len 3 gpa 0x10 val 0x1ffff10077c1010f > >After patch: > >syz-executor-13416 [002] .... 51302.299573: kvm_mmio: mmio write len 3 gpa 0x10 val 0xc1010f > >Reported-by: Dmitry Vyukov >Cc: Paolo Bonzini >Cc: Radim Krčmář >Signed-off-by: Wanpeng Li >--- >v2 -> v3: > * fix sparse warning >v1 -> v2: > * do the memcpy in kvm_mmio tracepoint > > arch/x86/kvm/x86.c | 8 ++++---- > include/trace/events/kvm.h | 6 ++++-- > 2 files changed, 8 insertions(+), 6 deletions(-) > >diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c >index daa1918..315ff2c 100644 >--- a/arch/x86/kvm/x86.c >+++ b/arch/x86/kvm/x86.c >@@ -4457,7 +4457,7 @@ static int vcpu_mmio_read(struct kvm_vcpu *vcpu, gpa_t addr, int len, void *v) > addr, n, v)) > && kvm_io_bus_read(vcpu, KVM_MMIO_BUS, addr, n, v)) > break; >- trace_kvm_mmio(KVM_TRACE_MMIO_READ, n, addr, *(u64 *)v); >+ trace_kvm_mmio(KVM_TRACE_MMIO_READ, n, addr, v); > handled += n; > addr += n; > len -= n; >@@ -4716,7 +4716,7 @@ static int read_prepare(struct kvm_vcpu *vcpu, void *val, int bytes) > { > if (vcpu->mmio_read_completed) { > trace_kvm_mmio(KVM_TRACE_MMIO_READ, bytes, >- vcpu->mmio_fragments[0].gpa, *(u64 *)val); >+ vcpu->mmio_fragments[0].gpa, val); > vcpu->mmio_read_completed = 0; > return 1; > } >@@ -4738,14 +4738,14 @@ static int write_emulate(struct kvm_vcpu *vcpu, gpa_t gpa, > > static int write_mmio(struct kvm_vcpu *vcpu, gpa_t gpa, int bytes, void *val) > { >- trace_kvm_mmio(KVM_TRACE_MMIO_WRITE, bytes, gpa, *(u64 *)val); >+ trace_kvm_mmio(KVM_TRACE_MMIO_WRITE, bytes, gpa, val); > return vcpu_mmio_write(vcpu, gpa, bytes, val); > } > > static int read_exit_mmio(struct kvm_vcpu *vcpu, gpa_t gpa, > void *val, int bytes) > { >- trace_kvm_mmio(KVM_TRACE_MMIO_READ_UNSATISFIED, bytes, gpa, 0); >+ trace_kvm_mmio(KVM_TRACE_MMIO_READ_UNSATISFIED, bytes, gpa, NULL); > return X86EMUL_IO_NEEDED; > } > >diff --git a/include/trace/events/kvm.h b/include/trace/events/kvm.h >index e4b0b8e..dfd2170 100644 >--- a/include/trace/events/kvm.h >+++ b/include/trace/events/kvm.h >@@ -211,7 +211,7 @@ TRACE_EVENT(kvm_ack_irq, > { KVM_TRACE_MMIO_WRITE, "write" } > > TRACE_EVENT(kvm_mmio, >- TP_PROTO(int type, int len, u64 gpa, u64 val), >+ TP_PROTO(int type, int len, u64 gpa, void *val), > TP_ARGS(type, len, gpa, val), > > TP_STRUCT__entry( >@@ -225,7 +225,9 @@ TRACE_EVENT(kvm_mmio, > __entry->type = type; > __entry->len = len; > __entry->gpa = gpa; >- __entry->val = val; >+ __entry->val = 0; >+ if (val) >+ memcpy(&__entry->val, val, min(8, len)); > ), > > TP_printk("mmio %s len %u gpa 0x%llx val 0x%llx", >-- >2.7.4 >