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authorWanpeng Li <wanpeng.li@hotmail.com>2017-12-14 17:40:50 -0800
committerPaolo Bonzini <pbonzini@redhat.com>2017-12-18 12:57:01 +0100
commite39d200fa5bf5b94a0948db0dae44c1b73b84a56 (patch)
treeeade29341276edb33b812335600ac2434e152084 /virt/kvm
parentf29810335965ac1f7bcb501ee2af5f039f792416 (diff)
KVM: Fix stack-out-of-bounds read in write_mmio
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 leaks 5 bytes from the kernel stack (CVE-2017-17741). This patch fixes it by just accessing the bytes which we operate 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> Reviewed-by: Darren Kenny <darren.kenny@oracle.com> Reviewed-by: Marc Zyngier <marc.zyngier@arm.com> Tested-by: Marc Zyngier <marc.zyngier@arm.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> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'virt/kvm')
-rw-r--r--virt/kvm/arm/mmio.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/virt/kvm/arm/mmio.c b/virt/kvm/arm/mmio.c
index b6e715fd3c90..dac7ceb1a677 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);