diff options
| author | Vitaly Kuznetsov <vkuznets@redhat.com> | 2020-06-05 13:59:05 +0200 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2020-06-08 07:59:08 -0400 |
| commit | 7a35e515a7055f483f87d12041c41db11b36c9ee (patch) | |
| tree | ad1212895544dbde97aa68f966363cf8921da8c6 /arch/x86/kvm/vmx/vmx.h | |
| parent | 34d2618d3318bf4832a13ef71c96833dc996f7d5 (diff) | |
KVM: VMX: Properly handle kvm_read/write_guest_virt*() result
Syzbot reports the following issue:
WARNING: CPU: 0 PID: 6819 at arch/x86/kvm/x86.c:618
kvm_inject_emulated_page_fault+0x210/0x290 arch/x86/kvm/x86.c:618
...
Call Trace:
...
RIP: 0010:kvm_inject_emulated_page_fault+0x210/0x290 arch/x86/kvm/x86.c:618
...
nested_vmx_get_vmptr+0x1f9/0x2a0 arch/x86/kvm/vmx/nested.c:4638
handle_vmon arch/x86/kvm/vmx/nested.c:4767 [inline]
handle_vmon+0x168/0x3a0 arch/x86/kvm/vmx/nested.c:4728
vmx_handle_exit+0x29c/0x1260 arch/x86/kvm/vmx/vmx.c:6067
'exception' we're trying to inject with kvm_inject_emulated_page_fault()
comes from:
nested_vmx_get_vmptr()
kvm_read_guest_virt()
kvm_read_guest_virt_helper()
vcpu->arch.walk_mmu->gva_to_gpa()
but it is only set when GVA to GPA conversion fails. In case it doesn't but
we still fail kvm_vcpu_read_guest_page(), X86EMUL_IO_NEEDED is returned and
nested_vmx_get_vmptr() calls kvm_inject_emulated_page_fault() with zeroed
'exception'. This happen when the argument is MMIO.
Paolo also noticed that nested_vmx_get_vmptr() is not the only place in
KVM code where kvm_read/write_guest_virt*() return result is mishandled.
VMX instructions along with INVPCID have the same issue. This was already
noticed before, e.g. see commit 541ab2aeb282 ("KVM: x86: work around
leak of uninitialized stack contents") but was never fully fixed.
KVM could've handled the request correctly by going to userspace and
performing I/O but there doesn't seem to be a good need for such requests
in the first place.
Introduce vmx_handle_memory_failure() as an interim solution.
Note, nested_vmx_get_vmptr() now has three possible outcomes: OK, PF,
KVM_EXIT_INTERNAL_ERROR and callers need to know if userspace exit is
needed (for KVM_EXIT_INTERNAL_ERROR) in case of failure. We don't seem
to have a good enum describing this tristate, just add "int *ret" to
nested_vmx_get_vmptr() interface to pass the information.
Reported-by: syzbot+2a7156e11dc199bdbd8a@syzkaller.appspotmail.com
Suggested-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20200605115906.532682-1-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/vmx/vmx.h')
| -rw-r--r-- | arch/x86/kvm/vmx/vmx.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h index 672c28f17e49..8a83b5edc820 100644 --- a/arch/x86/kvm/vmx/vmx.h +++ b/arch/x86/kvm/vmx/vmx.h @@ -355,6 +355,8 @@ struct shared_msr_entry *find_msr_entry(struct vcpu_vmx *vmx, u32 msr); void pt_update_intercept_for_msr(struct vcpu_vmx *vmx); void vmx_update_host_rsp(struct vcpu_vmx *vmx, unsigned long host_rsp); int vmx_find_msr_index(struct vmx_msrs *m, u32 msr); +int vmx_handle_memory_failure(struct kvm_vcpu *vcpu, int r, + struct x86_exception *e); #define POSTED_INTR_ON 0 #define POSTED_INTR_SN 1 |