Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757169AbdLQCKS (ORCPT ); Sat, 16 Dec 2017 21:10:18 -0500 Received: from mail-ot0-f196.google.com ([74.125.82.196]:44248 "EHLO mail-ot0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756919AbdLQCKQ (ORCPT ); Sat, 16 Dec 2017 21:10:16 -0500 X-Google-Smtp-Source: ACJfBoswUeET3wvEvNyty/50tghBfHSaUMqaHpeQhcjj9Evh2AWhdTaojsWYLZrQi1QXrGSGVZ+/VKH2ltkRj+ntLLI= MIME-Version: 1.0 In-Reply-To: <15b7b9e5-5b11-f20f-0260-5c8b9fc5e111@arm.com> References: <1513302050-14253-1-git-send-email-wanpeng.li@hotmail.com> <15b7b9e5-5b11-f20f-0260-5c8b9fc5e111@arm.com> From: Wanpeng Li Date: Sun, 17 Dec 2017 10:10:15 +0800 Message-ID: Subject: Re: [PATCH v4] KVM: Fix stack-out-of-bounds read in write_mmio To: Marc Zyngier Cc: "linux-kernel@vger.kernel.org" , kvm , Paolo Bonzini , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Wanpeng Li , Christoffer Dall Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by nfs id vBH2APEO027385 Content-Length: 6951 Lines: 172 2017-12-15 19:06 GMT+08:00 Marc Zyngier : > On 15/12/17 01:40, 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 >> Cc: Marc Zyngier >> Cc: Christoffer Dall >> Signed-off-by: Wanpeng Li >> --- >> v3 -> v4: >> * fix the arm tracepoint >> 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 ++++-- >> virt/kvm/arm/mmio.c | 6 +++--- >> 3 files changed, 11 insertions(+), 9 deletions(-) >> >> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c >> index 0f82e2c..c7071e7 100644 >> --- a/arch/x86/kvm/x86.c >> +++ b/arch/x86/kvm/x86.c >> @@ -4456,7 +4456,7 @@ 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; >> @@ -4715,7 +4715,7 @@ 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; >> } >> @@ -4737,14 +4737,14 @@ 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)); > > I'm not fond of hardcoded sizes; they tend to break as people change the > code around. Consider using sizeof(__entry->val) instead of 8. > >> ), >> >> TP_printk("mmio %s len %u gpa 0x%llx val 0x%llx", >> diff --git a/virt/kvm/arm/mmio.c b/virt/kvm/arm/mmio.c >> index b6e715f..dac7ceb 100644 >> --- a/virt/kvm/arm/mmio.c >> +++ b/virt/kvm/arm/mmio.c >> @@ -112,7 +112,7 @@ int kvm_handle_mmio_return(struct kvm_vcpu *vcpu, struct kvm_run *run) >> } >> >> trace_kvm_mmio(KVM_TRACE_MMIO_READ, len, run->mmio.phys_addr, >> - data); >> + &data); >> data = vcpu_data_host_to_guest(vcpu, data, len); >> vcpu_set_reg(vcpu, vcpu->arch.mmio_decode.rt, data); >> } >> @@ -182,14 +182,14 @@ int io_mem_abort(struct kvm_vcpu *vcpu, struct kvm_run *run, >> data = vcpu_data_guest_to_host(vcpu, vcpu_get_reg(vcpu, rt), >> len); >> >> - trace_kvm_mmio(KVM_TRACE_MMIO_WRITE, len, fault_ipa, data); >> + trace_kvm_mmio(KVM_TRACE_MMIO_WRITE, len, fault_ipa, &data); >> kvm_mmio_write_buf(data_buf, len, data); >> >> ret = kvm_io_bus_write(vcpu, KVM_MMIO_BUS, fault_ipa, len, >> data_buf); >> } else { >> trace_kvm_mmio(KVM_TRACE_MMIO_READ_UNSATISFIED, len, >> - fault_ipa, 0); >> + fault_ipa, NULL); >> >> ret = kvm_io_bus_read(vcpu, KVM_MMIO_BUS, fault_ipa, len, >> data_buf); >> > > I've given it a go on an arm64 platform, which works as expected. > Assuming you address the above: > > Reviewed-by: Marc Zyngier > Tested-by: Marc Zyngier Thanks Marc. :) Regards, Wanpeng Li