Re: [PATCH v4] KVM: Fix stack-out-of-bounds read in write_mmio
2017-12-18 19:55 GMT+08:00 Paolo Bonzini: > On 15/12/2017 12:06, Marc Zyngier wrote: >> Assuming you address the above: >> >> Reviewed-by: Marc Zyngier >> Tested-by: Marc Zyngier > > Done as follows: > > diff --git a/include/trace/events/kvm.h b/include/trace/events/kvm.h > index dfd21708694f..0a016bd14c2d 100644 > --- a/include/trace/events/kvm.h > +++ b/include/trace/events/kvm.h > @@ -227,7 +227,8 @@ > __entry->gpa= gpa; > __entry->val = 0; > if (val) > - memcpy(&__entry->val, val, min(8, len)); > + memcpy(&__entry->val, val, > + min_t(u32, sizeof(__entry->val), len)); > ), > > TP_printk("mmio %s len %u gpa 0x%llx val 0x%llx", Thanks Paolo. :) Regards, Wanpeng Li
Re: [PATCH v4] KVM: Fix stack-out-of-bounds read in write_mmio
2017-12-18 19:55 GMT+08:00 Paolo Bonzini : > On 15/12/2017 12:06, Marc Zyngier wrote: >> Assuming you address the above: >> >> Reviewed-by: Marc Zyngier >> Tested-by: Marc Zyngier > > Done as follows: > > diff --git a/include/trace/events/kvm.h b/include/trace/events/kvm.h > index dfd21708694f..0a016bd14c2d 100644 > --- a/include/trace/events/kvm.h > +++ b/include/trace/events/kvm.h > @@ -227,7 +227,8 @@ > __entry->gpa= gpa; > __entry->val = 0; > if (val) > - memcpy(&__entry->val, val, min(8, len)); > + memcpy(&__entry->val, val, > + min_t(u32, sizeof(__entry->val), len)); > ), > > TP_printk("mmio %s len %u gpa 0x%llx val 0x%llx", Thanks Paolo. :) Regards, Wanpeng Li
Re: [PATCH v4] KVM: Fix stack-out-of-bounds read in write_mmio
On 18/12/17 11:55, Paolo Bonzini wrote: > On 15/12/2017 12:06, Marc Zyngier wrote: >> Assuming you address the above: >> >> Reviewed-by: Marc Zyngier>> Tested-by: Marc Zyngier > > Done as follows: > > diff --git a/include/trace/events/kvm.h b/include/trace/events/kvm.h > index dfd21708694f..0a016bd14c2d 100644 > --- a/include/trace/events/kvm.h > +++ b/include/trace/events/kvm.h > @@ -227,7 +227,8 @@ > __entry->gpa= gpa; > __entry->val = 0; > if (val) > - memcpy(&__entry->val, val, min(8, len)); > + memcpy(&__entry->val, val, > +min_t(u32, sizeof(__entry->val), len)); > ), > > TP_printk("mmio %s len %u gpa 0x%llx val 0x%llx", > Looks good to me. Thanks, M. -- Jazz is not dead. It just smells funny...
Re: [PATCH v4] KVM: Fix stack-out-of-bounds read in write_mmio
On 18/12/17 11:55, Paolo Bonzini wrote: > On 15/12/2017 12:06, Marc Zyngier wrote: >> Assuming you address the above: >> >> Reviewed-by: Marc Zyngier >> Tested-by: Marc Zyngier > > Done as follows: > > diff --git a/include/trace/events/kvm.h b/include/trace/events/kvm.h > index dfd21708694f..0a016bd14c2d 100644 > --- a/include/trace/events/kvm.h > +++ b/include/trace/events/kvm.h > @@ -227,7 +227,8 @@ > __entry->gpa= gpa; > __entry->val = 0; > if (val) > - memcpy(&__entry->val, val, min(8, len)); > + memcpy(&__entry->val, val, > +min_t(u32, sizeof(__entry->val), len)); > ), > > TP_printk("mmio %s len %u gpa 0x%llx val 0x%llx", > Looks good to me. Thanks, M. -- Jazz is not dead. It just smells funny...
Re: [PATCH v4] KVM: Fix stack-out-of-bounds read in write_mmio
On 15/12/2017 12:06, Marc Zyngier wrote: > Assuming you address the above: > > Reviewed-by: Marc Zyngier> Tested-by: Marc Zyngier Done as follows: diff --git a/include/trace/events/kvm.h b/include/trace/events/kvm.h index dfd21708694f..0a016bd14c2d 100644 --- a/include/trace/events/kvm.h +++ b/include/trace/events/kvm.h @@ -227,7 +227,8 @@ __entry->gpa= gpa; __entry->val = 0; if (val) - memcpy(&__entry->val, val, min(8, len)); + memcpy(&__entry->val, val, + min_t(u32, sizeof(__entry->val), len)); ), TP_printk("mmio %s len %u gpa 0x%llx val 0x%llx", Thanks, Paolo
Re: [PATCH v4] KVM: Fix stack-out-of-bounds read in write_mmio
On 15/12/2017 12:06, Marc Zyngier wrote: > Assuming you address the above: > > Reviewed-by: Marc Zyngier > Tested-by: Marc Zyngier Done as follows: diff --git a/include/trace/events/kvm.h b/include/trace/events/kvm.h index dfd21708694f..0a016bd14c2d 100644 --- a/include/trace/events/kvm.h +++ b/include/trace/events/kvm.h @@ -227,7 +227,8 @@ __entry->gpa= gpa; __entry->val = 0; if (val) - memcpy(&__entry->val, val, min(8, len)); + memcpy(&__entry->val, val, + min_t(u32, sizeof(__entry->val), len)); ), TP_printk("mmio %s len %u gpa 0x%llx val 0x%llx", Thanks, Paolo
Re: [PATCH v4] KVM: Fix stack-out-of-bounds read in write_mmio
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 8803259df7f8 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 0x110077c1010f >> >> 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
Re: [PATCH v4] KVM: Fix stack-out-of-bounds read in write_mmio
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 8803259df7f8 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 0x110077c1010f >> >> 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
Re: [PATCH v4] KVM: Fix stack-out-of-bounds read in write_mmio
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 8803259df7f8 by task syz-executor/32298 > > CPU: 6 PID: 32298 Comm: syz-executor Tainted: G OE4.15.0-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 0x110077c1010f > > 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
Re: [PATCH v4] KVM: Fix stack-out-of-bounds read in write_mmio
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 8803259df7f8 by task syz-executor/32298 > > CPU: 6 PID: 32298 Comm: syz-executor Tainted: G OE4.15.0-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 0x110077c1010f > > 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
Re: [PATCH v4] KVM: Fix stack-out-of-bounds read in write_mmio
Code-wise, that looks good to me now. I also don't have ARM handy to validate though - but it looks correct. Reviewed-by: Darren KennyThanks, Darren. On Thu, Dec 14, 2017 at 05:40:50PM -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 8803259df7f8 by task syz-executor/32298 CPU: 6 PID: 32298 Comm: syz-executor Tainted: G OE4.15.0-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 0x110077c1010f 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)); ), 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
Re: [PATCH v4] KVM: Fix stack-out-of-bounds read in write_mmio
Code-wise, that looks good to me now. I also don't have ARM handy to validate though - but it looks correct. Reviewed-by: Darren Kenny Thanks, Darren. On Thu, Dec 14, 2017 at 05:40:50PM -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 8803259df7f8 by task syz-executor/32298 CPU: 6 PID: 32298 Comm: syz-executor Tainted: G OE4.15.0-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 0x110077c1010f 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)); ), 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) }