From patchwork Fri Dec 15 01:40:50 2017

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Subject: [v4] KVM: Fix stack-out-of-bounds read in write_mmio

From: Wanpeng Li <kernellwp@gmail.com>

X-Patchwork-Id: 10113513

Message-Id: <1513302050-14253-1-git-send-email-wanpeng.li@hotmail.com>

To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org

Cc: Paolo Bonzini <pbonzini@redhat.com>,

 =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= <rkrcmar@redhat.com>,

 Wanpeng Li <wanpeng.li@hotmail.com>, Marc Zyngier <marc.zyngier@arm.com>,

 Christoffer Dall <christoffer.dall@linaro.org>

Date: Thu, 14 Dec 2017 17:40:50 -0800

From: Wanpeng Li <wanpeng.li@hotmail.com>

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 <dvyukov@google.com>

Cc: Paolo Bonzini <pbonzini@redhat.com>

Cc: Radim Krčmář <rkrcmar@redhat.com>

Cc: Marc Zyngier <marc.zyngier@arm.com>

Cc: Christoffer Dall <christoffer.dall@linaro.org>

Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>

Reviewed-by: Darren Kenny <darren.kenny@oracle.com>

Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>

Tested-by: Marc Zyngier <marc.zyngier@arm.com>

---

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);

From patchwork Mon Dec 18 11:55:05 2017

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Subject: [v4] KVM: Fix stack-out-of-bounds read in write_mmio

From: Paolo Bonzini <pbonzini@redhat.com>

X-Patchwork-Id: 10118879

Message-Id: <17d27b8d-908b-a740-1d2d-e92a8507f25b@redhat.com>

To: Marc Zyngier <marc.zyngier@arm.com>,

 Wanpeng Li <kernellwp@gmail.com>, linux-kernel@vger.kernel.org,

 kvm@vger.kernel.org

Cc: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= <rkrcmar@redhat.com>,

 Wanpeng Li <wanpeng.li@hotmail.com>,

 Christoffer Dall <christoffer.dall@linaro.org>

Date: Mon, 18 Dec 2017 12:55:05 +0100

On 15/12/2017 12:06, Marc Zyngier wrote:

> Assuming you address the above:

> 

> Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>

> Tested-by: Marc Zyngier <marc.zyngier@arm.com>

Done as follows:

Thanks,

Paolo

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",