From: Mihai Donțu <mdo...@bitdefender.com>
This event is sent when a #PF occurs due to a failed permission check
in the shadow page tables, for a page in which the introspection tool
has shown interest.
Signed-off-by: Mihai Donțu <mdo...@bitdefender.com>
Co-developed-by: Adalbert Lazăr <ala...@bitdefender.com>
Signed-off-by: Adalbert Lazăr <ala...@bitdefender.com>
---
Documentation/virt/kvm/kvmi.rst | 51 +++++++
arch/x86/include/asm/kvmi_host.h | 1 +
arch/x86/kvm/kvmi.c | 141 ++++++++++++++++++
include/uapi/linux/kvmi.h | 10 ++
.../testing/selftests/kvm/x86_64/kvmi_test.c | 76 ++++++++++
virt/kvm/introspection/kvmi.c | 115 ++++++++++++++
virt/kvm/introspection/kvmi_int.h | 9 ++
virt/kvm/introspection/kvmi_msg.c | 18 +++
8 files changed, 421 insertions(+)
diff --git a/Documentation/virt/kvm/kvmi.rst b/Documentation/virt/kvm/kvmi.rst
index 123b2360d2e0..b2e2a9edda77 100644
--- a/Documentation/virt/kvm/kvmi.rst
+++ b/Documentation/virt/kvm/kvmi.rst
@@ -554,6 +554,7 @@ the following events::
KVMI_EVENT_DESCRIPTOR
KVMI_EVENT_HYPERCALL
KVMI_EVENT_MSR
+ KVMI_EVENT_PF
KVMI_EVENT_XSETBV
When an event is enabled, the introspection tool is notified and
@@ -1387,3 +1388,53 @@ register (see **KVMI_VCPU_CONTROL_EVENTS**).
``kvmi_event``, the MSR number, the old value and the new value are
sent to the introspection tool. The *CONTINUE* action will set the ``new_val``.
+
+10. KVMI_EVENT_PF
+-----------------
+
+:Architectures: x86
+:Versions: >= 1
+:Actions: CONTINUE, CRASH, RETRY
+:Parameters:
+
+::
+
+ struct kvmi_event;
+ struct kvmi_event_pf {
+ __u64 gva;
+ __u64 gpa;
+ __u8 access;
+ __u8 padding1;
+ __u16 padding2;
+ __u32 padding3;
+ };
+
+:Returns:
+
+::
+
+ struct kvmi_vcpu_hdr;
+ struct kvmi_event_reply;
+
+This event is sent when a hypervisor page fault occurs due to a failed
+permission check in the shadow page tables, the introspection has been
+enabled for this event (see *KVMI_VCPU_CONTROL_EVENTS*) and the event was
+generated for a page in which the introspection tool has shown interest
+(ie. has previously touched it by adjusting the spte permissions).
+
+The shadow page tables can be used by the introspection tool to guarantee
+the purpose of code areas inside the guest (code, rodata, stack, heap
+etc.) Each attempt at an operation unfitting for a certain memory
+range (eg. execute code in heap) triggers a page fault and gives the
+introspection tool the chance to audit the code attempting the operation.
+
+``kvmi_event``, guest virtual address (or 0xffffffff/UNMAPPED_GVA),
+guest physical address and the access flags (eg. KVMI_PAGE_ACCESS_R)
+are sent to the introspection tool.
+
+The *CONTINUE* action will continue the page fault handling (e.g. via
+emulation).
+
+The *RETRY* action is used by the introspection tool to retry the
+execution of the current instruction, usually because it changed the
+instruction pointer or the page restrictions.
diff --git a/arch/x86/include/asm/kvmi_host.h b/arch/x86/include/asm/kvmi_host.h
index 98ea548c0b15..25c7bb8a9082 100644
--- a/arch/x86/include/asm/kvmi_host.h
+++ b/arch/x86/include/asm/kvmi_host.h
@@ -41,6 +41,7 @@ struct kvm_vcpu_arch_introspection {
};
struct kvm_arch_introspection {
+ struct kvm_page_track_notifier_node kptn_node;
};
#define SLOTS_SIZE BITS_TO_LONGS(KVM_MEM_SLOTS_NUM)
diff --git a/arch/x86/kvm/kvmi.c b/arch/x86/kvm/kvmi.c
index b233a3c5becb..8fbf1720749b 100644
--- a/arch/x86/kvm/kvmi.c
+++ b/arch/x86/kvm/kvmi.c
@@ -10,6 +10,21 @@
#include "cpuid.h"
#include "../../../virt/kvm/introspection/kvmi_int.h"
+static bool kvmi_track_preread(struct kvm_vcpu *vcpu, gpa_t gpa, gva_t gva,
+ int bytes,
+ struct kvm_page_track_notifier_node *node);
+static bool kvmi_track_prewrite(struct kvm_vcpu *vcpu, gpa_t gpa, gva_t gva,
+ const u8 *new, int bytes,
+ struct kvm_page_track_notifier_node *node);
+static bool kvmi_track_preexec(struct kvm_vcpu *vcpu, gpa_t gpa, gva_t gva,
+ struct kvm_page_track_notifier_node *node);
+static void kvmi_track_create_slot(struct kvm *kvm,
+ struct kvm_memory_slot *slot,
+ unsigned long npages,
+ struct kvm_page_track_notifier_node *node);
+static void kvmi_track_flush_slot(struct kvm *kvm, struct kvm_memory_slot
*slot,
+ struct kvm_page_track_notifier_node *node);
+
static unsigned int kvmi_vcpu_mode(const struct kvm_vcpu *vcpu,
const struct kvm_sregs *sregs)
{
@@ -1209,3 +1224,129 @@ void kvmi_arch_update_page_tracking(struct kvm *kvm,
}
}
}
+
+void kvmi_arch_hook(struct kvm *kvm)
+{
+ struct kvm_introspection *kvmi = KVMI(kvm);
+
+ kvmi->arch.kptn_node.track_preread = kvmi_track_preread;
+ kvmi->arch.kptn_node.track_prewrite = kvmi_track_prewrite;
+ kvmi->arch.kptn_node.track_preexec = kvmi_track_preexec;
+ kvmi->arch.kptn_node.track_create_slot = kvmi_track_create_slot;
+ kvmi->arch.kptn_node.track_flush_slot = kvmi_track_flush_slot;
+
+ kvm_page_track_register_notifier(kvm, &kvmi->arch.kptn_node);
+}
+
+void kvmi_arch_unhook(struct kvm *kvm)
+{
+ struct kvm_introspection *kvmi = KVMI(kvm);
+
+ kvm_page_track_unregister_notifier(kvm, &kvmi->arch.kptn_node);
+}
+
+static bool is_pf_of_interest(struct kvm_vcpu *vcpu, gpa_t gpa, u8 access)
+{
+ if (!kvm_x86_ops.spt_fault(vcpu))
+ return false;
+
+ if (kvm_x86_ops.gpt_translation_fault(vcpu))
+ return false;
+
+ return kvmi_restricted_page_access(KVMI(vcpu->kvm), gpa, access);
+}
+
+static bool handle_pf_event(struct kvm_vcpu *vcpu, gpa_t gpa, gva_t gva,
+ int access)
+{
+ if (!is_pf_of_interest(vcpu, gpa, access))
+ return true;
+
+ return kvmi_pf_event(vcpu, gpa, gva, access);
+}
+
+static bool kvmi_track_preread(struct kvm_vcpu *vcpu, gpa_t gpa, gva_t gva,
+ int bytes,
+ struct kvm_page_track_notifier_node *node)
+{
+ struct kvm_introspection *kvmi;
+ bool ret = true;
+
+ kvmi = kvmi_get(vcpu->kvm);
+ if (!kvmi)
+ return true;
+
+ if (is_event_enabled(vcpu, KVMI_EVENT_PF))
+ ret = handle_pf_event(vcpu, gpa, gva, KVMI_PAGE_ACCESS_R);
+
+ kvmi_put(vcpu->kvm);
+
+ return ret;
+}
+
+static bool kvmi_track_prewrite(struct kvm_vcpu *vcpu, gpa_t gpa, gva_t gva,
+ const u8 *new, int bytes,
+ struct kvm_page_track_notifier_node *node)
+{
+ struct kvm_introspection *kvmi;
+ bool ret = true;
+
+ kvmi = kvmi_get(vcpu->kvm);
+ if (!kvmi)
+ return true;
+
+ if (is_event_enabled(vcpu, KVMI_EVENT_PF))
+ ret = handle_pf_event(vcpu, gpa, gva, KVMI_PAGE_ACCESS_W);
+
+ kvmi_put(vcpu->kvm);
+
+ return ret;
+}
+
+static bool kvmi_track_preexec(struct kvm_vcpu *vcpu, gpa_t gpa, gva_t gva,
+ struct kvm_page_track_notifier_node *node)
+{
+ struct kvm_introspection *kvmi;
+ bool ret = true;
+
+ kvmi = kvmi_get(vcpu->kvm);
+ if (!kvmi)
+ return true;
+
+ if (is_event_enabled(vcpu, KVMI_EVENT_PF))
+ ret = handle_pf_event(vcpu, gpa, gva, KVMI_PAGE_ACCESS_X);
+
+ kvmi_put(vcpu->kvm);
+
+ return ret;
+}
+
+static void kvmi_track_create_slot(struct kvm *kvm,
+ struct kvm_memory_slot *slot,
+ unsigned long npages,
+ struct kvm_page_track_notifier_node *node)
+{
+ struct kvm_introspection *kvmi;
+
+ kvmi = kvmi_get(kvm);
+ if (!kvmi)
+ return;
+
+ kvmi_add_memslot(kvm, slot, npages);
+
+ kvmi_put(kvm);
+}
+
+static void kvmi_track_flush_slot(struct kvm *kvm, struct kvm_memory_slot
*slot,
+ struct kvm_page_track_notifier_node *node)
+{
+ struct kvm_introspection *kvmi;
+
+ kvmi = kvmi_get(kvm);
+ if (!kvmi)
+ return;
+
+ kvmi_remove_memslot(kvm, slot);
+
+ kvmi_put(kvm);
+}
diff --git a/include/uapi/linux/kvmi.h b/include/uapi/linux/kvmi.h
index dc82f192534c..dc7ba12498b7 100644
--- a/include/uapi/linux/kvmi.h
+++ b/include/uapi/linux/kvmi.h
@@ -60,6 +60,7 @@ enum {
KVMI_EVENT_XSETBV = 6,
KVMI_EVENT_DESCRIPTOR = 7,
KVMI_EVENT_MSR = 8,
+ KVMI_EVENT_PF = 9,
KVMI_NUM_EVENTS
};
@@ -218,4 +219,13 @@ struct kvmi_vcpu_inject_exception {
__u64 address;
};
+struct kvmi_event_pf {
+ __u64 gva;
+ __u64 gpa;
+ __u8 access;
+ __u8 padding1;
+ __u16 padding2;
+ __u32 padding3;
+};
+
#endif /* _UAPI__LINUX_KVMI_H */
diff --git a/tools/testing/selftests/kvm/x86_64/kvmi_test.c
b/tools/testing/selftests/kvm/x86_64/kvmi_test.c
index 4fb109cec1b4..21b3f7a459c8 100644
--- a/tools/testing/selftests/kvm/x86_64/kvmi_test.c
+++ b/tools/testing/selftests/kvm/x86_64/kvmi_test.c
@@ -42,6 +42,11 @@ struct vcpu_reply {
struct kvmi_event_reply reply;
};
+struct pf_ev {
+ struct kvmi_event common;
+ struct kvmi_event_pf pf;
+};
+
struct vcpu_worker_data {
struct kvm_vm *vm;
int vcpu_id;
@@ -51,6 +56,10 @@ struct vcpu_worker_data {
bool restart_on_shutdown;
};
+typedef void (*fct_pf_event)(struct kvm_vm *vm, struct kvmi_msg_hdr *hdr,
+ struct pf_ev *ev,
+ struct vcpu_reply *rpl);
+
enum {
GUEST_TEST_NOOP = 0,
GUEST_TEST_BP,
@@ -58,6 +67,7 @@ enum {
GUEST_TEST_DESCRIPTOR,
GUEST_TEST_HYPERCALL,
GUEST_TEST_MSR,
+ GUEST_TEST_PF,
GUEST_TEST_XSETBV,
};
@@ -111,6 +121,11 @@ static void guest_msr_test(void)
wrmsr(MSR_MISC_FEATURES_ENABLES, msr);
}
+static void guest_pf_test(void)
+{
+ *((uint8_t *)test_gva) = READ_ONCE(test_write_pattern);
+}
+
/* from fpu/internal.h */
static u64 xgetbv(u32 index)
{
@@ -171,6 +186,9 @@ static void guest_code(void)
case GUEST_TEST_MSR:
guest_msr_test();
break;
+ case GUEST_TEST_PF:
+ guest_pf_test();
+ break;
case GUEST_TEST_XSETBV:
guest_xsetbv_test();
break;
@@ -1860,6 +1878,63 @@ static void test_cmd_vm_set_page_access(struct kvm_vm
*vm)
set_page_access(gpa, full_access);
}
+static void test_pf(struct kvm_vm *vm, fct_pf_event cbk)
+{
+ __u16 event_id = KVMI_EVENT_PF;
+ struct vcpu_worker_data data = {
+ .vm = vm,
+ .vcpu_id = VCPU_ID,
+ .test_id = GUEST_TEST_PF,
+ };
+ struct kvmi_msg_hdr hdr;
+ struct vcpu_reply rpl = {};
+ pthread_t vcpu_thread;
+ struct pf_ev ev;
+
+ set_page_access(test_gpa, KVMI_PAGE_ACCESS_R);
+ enable_vcpu_event(vm, event_id);
+
+ new_test_write_pattern(vm);
+
+ vcpu_thread = start_vcpu_worker(&data);
+
+ receive_event(&hdr, &ev.common, sizeof(ev), event_id);
+
+ pr_info("PF event, gpa 0x%llx, gva 0x%llx, access 0x%x\n",
+ ev.pf.gpa, ev.pf.gva, ev.pf.access);
+
+ TEST_ASSERT(ev.pf.gpa == test_gpa && ev.pf.gva == test_gva,
+ "Unexpected #PF event, gpa 0x%llx (expended 0x%lx), gva 0x%llx
(expected 0x%lx)\n",
+ ev.pf.gpa, test_gpa, ev.pf.gva, test_gva);
+
+ cbk(vm, &hdr, &ev, &rpl);
+
+ stop_vcpu_worker(vcpu_thread, &data);
+
+ TEST_ASSERT(*((uint8_t *)test_hva) == test_write_pattern,
+ "Write failed, expected 0x%x, result 0x%x\n",
+ test_write_pattern, *((uint8_t *)test_hva));
+
+ disable_vcpu_event(vm, event_id);
+ set_page_access(test_gpa, KVMI_PAGE_ACCESS_R
+ | KVMI_PAGE_ACCESS_W
+ | KVMI_PAGE_ACCESS_X);
+}
+
+static void cbk_test_event_pf(struct kvm_vm *vm, struct kvmi_msg_hdr *hdr,
+ struct pf_ev *ev, struct vcpu_reply *rpl)
+{
+ set_page_access(test_gpa, KVMI_PAGE_ACCESS_R | KVMI_PAGE_ACCESS_W);
+
+ reply_to_event(hdr, &ev->common, KVMI_EVENT_ACTION_RETRY,
+ rpl, sizeof(*rpl));
+}
+
+static void test_event_pf(struct kvm_vm *vm)
+{
+ test_pf(vm, cbk_test_event_pf);
+}
+
static void test_introspection(struct kvm_vm *vm)
{
srandom(time(0));
@@ -1893,6 +1968,7 @@ static void test_introspection(struct kvm_vm *vm)
test_event_descriptor(vm);
test_cmd_vcpu_control_msr(vm);
test_cmd_vm_set_page_access(vm);
+ test_event_pf(vm);
unhook_introspection(vm);
}
diff --git a/virt/kvm/introspection/kvmi.c b/virt/kvm/introspection/kvmi.c
index b57ad490dd06..99c88e182587 100644
--- a/virt/kvm/introspection/kvmi.c
+++ b/virt/kvm/introspection/kvmi.c
@@ -113,6 +113,7 @@ static void setup_known_events(void)
set_bit(KVMI_EVENT_HYPERCALL, Kvmi_known_vcpu_events);
set_bit(KVMI_EVENT_MSR, Kvmi_known_vcpu_events);
set_bit(KVMI_EVENT_PAUSE_VCPU, Kvmi_known_vcpu_events);
+ set_bit(KVMI_EVENT_PF, Kvmi_known_vcpu_events);
set_bit(KVMI_EVENT_TRAP, Kvmi_known_vcpu_events);
set_bit(KVMI_EVENT_XSETBV, Kvmi_known_vcpu_events);
@@ -368,6 +369,8 @@ static void __kvmi_unhook(struct kvm *kvm)
struct kvm_introspection *kvmi = KVMI(kvm);
wait_for_completion_killable(&kvm->kvmi_complete);
+
+ kvmi_arch_unhook(kvm);
kvmi_sock_put(kvmi);
}
@@ -415,6 +418,8 @@ static int __kvmi_hook(struct kvm *kvm,
if (!kvmi_sock_get(kvmi, hook->fd))
return -EINVAL;
+ kvmi_arch_hook(kvm);
+
return 0;
}
@@ -1182,3 +1187,113 @@ int kvmi_cmd_set_page_access(struct kvm_introspection
*kvmi,
return ec;
}
+
+static int kvmi_get_gfn_access(struct kvm_introspection *kvmi, const gfn_t gfn,
+ u8 *access)
+{
+ struct kvmi_mem_access *m;
+
+ read_lock(&kvmi->access_tree_lock);
+ m = __kvmi_get_gfn_access(kvmi, gfn);
+ if (m)
+ *access = m->access;
+ read_unlock(&kvmi->access_tree_lock);
+
+ return m ? 0 : -1;
+}
+
+bool kvmi_restricted_page_access(struct kvm_introspection *kvmi, gpa_t gpa,
+ u8 access)
+{
+ u8 allowed_access;
+ int err;
+
+ err = kvmi_get_gfn_access(kvmi, gpa_to_gfn(gpa), &allowed_access);
+ if (err)
+ return false;
+
+ /*
+ * We want to be notified only for violations involving access
+ * bits that we've specifically cleared
+ */
+ if (access & (~allowed_access))
+ return true;
+
+ return false;
+}
+
+bool kvmi_pf_event(struct kvm_vcpu *vcpu, gpa_t gpa, gva_t gva, u8 access)
+{
+ bool ret = false;
+ u32 action;
+
+ action = kvmi_msg_send_pf(vcpu, gpa, gva, access);
+
+ switch (action) {
+ case KVMI_EVENT_ACTION_CONTINUE:
+ ret = true;
+ break;
+ case KVMI_EVENT_ACTION_RETRY:
+ break;
+ default:
+ kvmi_handle_common_event_actions(vcpu->kvm, action);
+ }
+
+ return ret;
+}
+
+void kvmi_add_memslot(struct kvm *kvm, struct kvm_memory_slot *slot,
+ unsigned long npages)
+{
+ struct kvm_introspection *kvmi = KVMI(kvm);
+ gfn_t start = slot->base_gfn;
+ gfn_t end = start + npages;
+ int idx;
+
+ idx = srcu_read_lock(&kvm->srcu);
+ spin_lock(&kvm->mmu_lock);
+ read_lock(&kvmi->access_tree_lock);
+
+ while (start < end) {
+ struct kvmi_mem_access *m;
+
+ m = __kvmi_get_gfn_access(kvmi, start);
+ if (m)
+ kvmi_arch_update_page_tracking(kvm, slot, m);
+ start++;
+ }
+
+ read_unlock(&kvmi->access_tree_lock);
+ spin_unlock(&kvm->mmu_lock);
+ srcu_read_unlock(&kvm->srcu, idx);
+}
+
+void kvmi_remove_memslot(struct kvm *kvm, struct kvm_memory_slot *slot)
+{
+ struct kvm_introspection *kvmi = KVMI(kvm);
+ gfn_t start = slot->base_gfn;
+ gfn_t end = start + slot->npages;
+ int idx;
+
+ idx = srcu_read_lock(&kvm->srcu);
+ spin_lock(&kvm->mmu_lock);
+ write_lock(&kvmi->access_tree_lock);
+
+ while (start < end) {
+ struct kvmi_mem_access *m;
+
+ m = __kvmi_get_gfn_access(kvmi, start);
+ if (m) {
+ u8 prev_access = m->access;
+
+ m->access = full_access;
+ kvmi_arch_update_page_tracking(kvm, slot, m);
+ m->access = prev_access;
+ }
+ start++;
+ }
+
+ write_unlock(&kvmi->access_tree_lock);
+ spin_unlock(&kvm->mmu_lock);
+ srcu_read_unlock(&kvm->srcu, idx);
+}
diff --git a/virt/kvm/introspection/kvmi_int.h
b/virt/kvm/introspection/kvmi_int.h
index 024e7acf0dce..9f2341fe21d5 100644
--- a/virt/kvm/introspection/kvmi_int.h
+++ b/virt/kvm/introspection/kvmi_int.h
@@ -47,6 +47,7 @@ int kvmi_msg_send_unhook(struct kvm_introspection *kvmi);
u32 kvmi_msg_send_vcpu_pause(struct kvm_vcpu *vcpu);
u32 kvmi_msg_send_hypercall(struct kvm_vcpu *vcpu);
u32 kvmi_msg_send_bp(struct kvm_vcpu *vcpu, u64 gpa, u8 insn_len);
+u32 kvmi_msg_send_pf(struct kvm_vcpu *vcpu, u64 gpa, u64 gva, u8 access);
/* kvmi.c */
void *kvmi_msg_alloc(void);
@@ -82,6 +83,12 @@ int kvmi_cmd_vcpu_set_registers(struct kvm_vcpu *vcpu,
int kvmi_cmd_set_page_access(struct kvm_introspection *kvmi,
const struct kvmi_msg_hdr *msg,
const struct kvmi_vm_set_page_access *req);
+bool kvmi_restricted_page_access(struct kvm_introspection *kvmi, gpa_t gpa,
+ u8 access);
+bool kvmi_pf_event(struct kvm_vcpu *vcpu, gpa_t gpa, gva_t gva, u8 access);
+void kvmi_add_memslot(struct kvm *kvm, struct kvm_memory_slot *slot,
+ unsigned long npages);
+void kvmi_remove_memslot(struct kvm *kvm, struct kvm_memory_slot *slot);
/* arch */
bool kvmi_arch_vcpu_alloc_interception(struct kvm_vcpu *vcpu);
@@ -129,5 +136,7 @@ int kvmi_arch_cmd_vcpu_control_msr(struct kvm_vcpu *vcpu,
void kvmi_arch_update_page_tracking(struct kvm *kvm,
struct kvm_memory_slot *slot,
struct kvmi_mem_access *m);
+void kvmi_arch_hook(struct kvm *kvm);
+void kvmi_arch_unhook(struct kvm *kvm);
#endif
diff --git a/virt/kvm/introspection/kvmi_msg.c
b/virt/kvm/introspection/kvmi_msg.c
index f7ffb971f1dc..0a0d10b43f2d 100644
--- a/virt/kvm/introspection/kvmi_msg.c
+++ b/virt/kvm/introspection/kvmi_msg.c
@@ -983,3 +983,21 @@ u32 kvmi_msg_send_bp(struct kvm_vcpu *vcpu, u64 gpa, u8
insn_len)
return action;
}
+
+u32 kvmi_msg_send_pf(struct kvm_vcpu *vcpu, u64 gpa, u64 gva, u8 access)
+{
+ struct kvmi_event_pf e;
+ int err, action;
+
+ memset(&e, 0, sizeof(e));
+ e.gpa = gpa;
+ e.gva = gva;
+ e.access = access;
+
+ err = kvmi_send_event(vcpu, KVMI_EVENT_PF, &e, sizeof(e),
+ NULL, 0, &action);
+ if (err)
+ return KVMI_EVENT_ACTION_CONTINUE;
+
+ return action;
+}
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