From: Wanpeng Li <[email protected]>
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 <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Radim Krčmář <[email protected]>
Cc: Marc Zyngier <[email protected]>
Cc: Christoffer Dall <[email protected]>
Signed-off-by: Wanpeng Li <[email protected]>
---
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)
}
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);
--
2.7.4
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 <[email protected]>
Thanks,
Darren.
On Thu, Dec 14, 2017 at 05:40:50PM -0800, Wanpeng Li wrote:
>From: Wanpeng Li <[email protected]>
>
>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 <[email protected]>
>Cc: Paolo Bonzini <[email protected]>
>Cc: Radim Krčmář <[email protected]>
>Cc: Marc Zyngier <[email protected]>
>Cc: Christoffer Dall <[email protected]>
>Signed-off-by: Wanpeng Li <[email protected]>
>---
>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)
> }
>
> 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);
>--
>2.7.4
>
On 15/12/17 01:40, Wanpeng Li wrote:
> From: Wanpeng Li <[email protected]>
>
> 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 <[email protected]>
> Cc: Paolo Bonzini <[email protected]>
> Cc: Radim Krčmář <[email protected]>
> Cc: Marc Zyngier <[email protected]>
> Cc: Christoffer Dall <[email protected]>
> Signed-off-by: Wanpeng Li <[email protected]>
> ---
> 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 <[email protected]>
Tested-by: Marc Zyngier <[email protected]>
Thanks,
M.
--
Jazz is not dead. It just smells funny...
2017-12-15 19:06 GMT+08:00 Marc Zyngier <[email protected]>:
> On 15/12/17 01:40, Wanpeng Li wrote:
>> From: Wanpeng Li <[email protected]>
>>
>> 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 <[email protected]>
>> Cc: Paolo Bonzini <[email protected]>
>> Cc: Radim Krčmář <[email protected]>
>> Cc: Marc Zyngier <[email protected]>
>> Cc: Christoffer Dall <[email protected]>
>> Signed-off-by: Wanpeng Li <[email protected]>
>> ---
>> 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 <[email protected]>
> Tested-by: Marc Zyngier <[email protected]>
Thanks Marc. :)
Regards,
Wanpeng Li
On 15/12/2017 12:06, Marc Zyngier wrote:
> Assuming you address the above:
>
> Reviewed-by: Marc Zyngier <[email protected]>
> Tested-by: Marc Zyngier <[email protected]>
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
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 <[email protected]>
>> Tested-by: Marc Zyngier <[email protected]>
>
> 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...
2017-12-18 19:55 GMT+08:00 Paolo Bonzini <[email protected]>:
> On 15/12/2017 12:06, Marc Zyngier wrote:
>> Assuming you address the above:
>>
>> Reviewed-by: Marc Zyngier <[email protected]>
>> Tested-by: Marc Zyngier <[email protected]>
>
> 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