Check if the emulator reveals host's kernel memory address.
Signed-off-by: Michal Luczaj <mhal@xxxxxxx>
---
Although checkpatch complains about the use of `extern`, I am sending this
as it is. Let me know if you need it in some better form.
[unpatched]$ ./tools/testing/selftests/kvm/x86_64/emulator_illegal_lea
==== Test Assertion Failure ====
x86_64/emulator_illegal_lea.c:129: uc->args[0] == 0
pid=957 tid=957 errno=4 - Interrupted system call
1 : check_state at emulator_illegal_lea.c:129
2 : main at emulator_illegal_lea.c:169 (discriminator 1)
3 : ?? ??:0
4 : ?? ??:0
5 : _start at ??:?
Host's address leaked: 0xffff88811a5d3620 (2)
[patched]$ ./tools/testing/selftests/kvm/x86_64/emulator_illegal_lea
[patched]$
tools/testing/selftests/kvm/.gitignore | 1 +
tools/testing/selftests/kvm/Makefile | 1 +
.../kvm/x86_64/emulator_illegal_lea.c | 180 ++++++++++++++++++
3 files changed, 182 insertions(+)
create mode 100644 tools/testing/selftests/kvm/x86_64/emulator_illegal_lea.c
diff --git a/tools/testing/selftests/kvm/.gitignore b/tools/testing/selftests/kvm/.gitignore
index 4509a3a7eeae..8977458080b9 100644
--- a/tools/testing/selftests/kvm/.gitignore
+++ b/tools/testing/selftests/kvm/.gitignore
@@ -17,6 +17,7 @@
/x86_64/debug_regs
/x86_64/evmcs_test
/x86_64/emulator_error_test
+/x86_64/emulator_illegal_lea
/x86_64/fix_hypercall_test
/x86_64/get_msr_index_features
/x86_64/kvm_clock_test
diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
index 22423c871ed6..453cd34e1fde 100644
--- a/tools/testing/selftests/kvm/Makefile
+++ b/tools/testing/selftests/kvm/Makefile
@@ -75,6 +75,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/cr4_cpuid_sync_test
TEST_GEN_PROGS_x86_64 += x86_64/get_msr_index_features
TEST_GEN_PROGS_x86_64 += x86_64/evmcs_test
TEST_GEN_PROGS_x86_64 += x86_64/emulator_error_test
+TEST_GEN_PROGS_x86_64 += x86_64/emulator_illegal_lea
TEST_GEN_PROGS_x86_64 += x86_64/fix_hypercall_test
TEST_GEN_PROGS_x86_64 += x86_64/hyperv_clock
TEST_GEN_PROGS_x86_64 += x86_64/hyperv_cpuid
diff --git a/tools/testing/selftests/kvm/x86_64/emulator_illegal_lea.c b/tools/testing/selftests/kvm/x86_64/emulator_illegal_lea.c
new file mode 100644
index 000000000000..5f0704e04fac
--- /dev/null
+++ b/tools/testing/selftests/kvm/x86_64/emulator_illegal_lea.c
@@ -0,0 +1,180 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Test for handling of illegal (ModRM mod = 3) LEA.
+ *
+ * To trigger the emulator and feed it with LEA, we VM-exit on IO (with a
+ * single OUTS), then race decoder's instruction fetch - hoping to replace the
+ * initial IO op with an illegal LEA.
+ */
+
+#include "test_util.h"
+#include "kvm_util.h"
+#include "processor.h"
+
+#include <string.h>
+#include <pthread.h>
+#include <sys/mman.h>
+
+/* defined in tools/testing/selftests/kvm/lib/x86_64/ucall.c */
+#define UCALL_PIO_PORT ((uint16_t)0x1000)
+
+#define VCPU_ID 0
+#define NOT_UCALL_PORT ((uint16_t)~UCALL_PIO_PORT)
+#define MAX_ATTEMPTS 0x10000
+#define MAYBE_KERNEL(addr) ((int64_t)(addr) < 0)
+
+extern uint32_t race_op;
+
+static void guest_ud_handler(struct ex_regs *regs)
+{
+ GUEST_ASSERT(regs->rip == (uint64_t)&race_op);
+ regs->rip += 4;
+}
+
+__aligned(0x1000) __attribute__((naked)) static void guest_code(void)
+{
+ uint32_t n = 1;
+ void *readable;
+ uint64_t rax;
+
+ do {
+ rax = 0;
+ readable = &guest_code;
+ /*
+ * This is where
+ * 3e 3e 3e 6f outsl (%rsi), %dx
+ * will be turned into
+ * 3e 48 8d c0 lea rax (!), rax
+ * Both instructions padded to 32 bits with DS prefixes.
+ */
+ asm volatile(".align 8\n\t"
+ "race_op:\n\t"
+ "ds\n\t"
+ "ds\n\t"
+ "ds\n\t"
+ "outsl (%[readable]), %[port]\n\t"
+ ".fill 8, 1, 0x90"
+ : [rax] "=a" (rax)
+ : [readable] "S" (readable),
+ [port] "d" (NOT_UCALL_PORT));
+ } while (!MAYBE_KERNEL(rax) && n++ < MAX_ATTEMPTS);
+
+ ucall(UCALL_DONE, 2, rax, n);
+}
+
+__attribute__((naked)) static void asm_lea(void)
+{
+ asm volatile("ds\n\t"
+ "lea (%rax), %rax");
+}
+
+__attribute__((naked)) static void asm_outs(void)
+{
+ asm volatile("ds\n\t"
+ "ds\n\t"
+ "ds\n\t"
+ "outsl (%rsi), %dx");
+}
+
+void *racer(void *arg)
+{
+ uint32_t *ptr = arg;
+ uint32_t lea, outs;
+
+ memcpy(&lea, &asm_lea, sizeof(lea));
+ /* set modrm mod = 3 */
+ lea |= 0xc0000000;
+
+ memcpy(&outs, &asm_outs, sizeof(outs));
+
+ while (true) {
+ *ptr = outs;
+ sched_yield();
+ *ptr = lea;
+ sched_yield();
+ pthread_testcancel();
+ };
+}
+
+int check_exit_reason(struct kvm_run *run)
+{
+ switch (run->exit_reason) {
+ case KVM_EXIT_IO:
+ /* race lost: OUTS was executed; ignore and retry */
+ TEST_ASSERT(run->io.port == NOT_UCALL_PORT,
+ "Unexpected IO port: %u",
+ run->io.port);
+ return 1;
+ case KVM_EXIT_INTERNAL_ERROR:
+ /* emulator hit bad LEA and bailed out; well done */
+ ASSERT_EQ(*(uint32_t *)&run->emulation_failure.insn_bytes,
+ *(uint32_t *)&asm_lea | 0xc0000000);
+ TEST_ASSERT(run->internal.suberror == KVM_INTERNAL_ERROR_EMULATION,
+ "Unexpected suberror: %u",
+ run->internal.suberror);
+ return 0;
+ default:
+ TEST_FAIL("Unexpected VM exit: %s",
+ exit_reason_str(run->exit_reason));
+ }
+
+ __builtin_unreachable();
+}
+
+int check_state(struct kvm_run *run, struct ucall *uc)
+{
+ switch (uc->cmd) {
+ case UCALL_NONE:
+ return check_exit_reason(run);
+ case UCALL_DONE:
+ TEST_ASSERT(uc->args[0] == 0,
+ "Host's address leaked: %#lx (%lu)",
+ uc->args[0], uc->args[1]);
+ return 0;
+ case UCALL_ABORT:
+ TEST_FAIL("UCALL_ABORT: %s, line %ld\n",
+ (char *)uc->args[0], uc->args[1]);
+ case UCALL_UNHANDLED:
+ TEST_FAIL("UCALL_UNHANDLED: #%ld\n", uc->args[0]);
+ default:
+ TEST_FAIL("Unexpected ucall");
+ }
+
+ __builtin_unreachable();
+}
+
+int main(int argc, char *argv[])
+{
+ struct kvm_run *run;
+ struct kvm_vm *vm;
+ pthread_t thread;
+ struct ucall uc;
+ int ret;
+
+ ret = mprotect(&guest_code, 0x1000, PROT_READ | PROT_WRITE | PROT_EXEC);
+ TEST_ASSERT(ret == 0, "mprotect() failed: %s", strerror(errno));
+
+ vm = vm_create_default(VCPU_ID, 0, (void *)guest_code);
+ run = vcpu_state(vm, VCPU_ID);
+
+ vm_init_descriptor_tables(vm);
+ vcpu_init_descriptor_tables(vm, VCPU_ID);
+ vm_install_exception_handler(vm, UD_VECTOR, guest_ud_handler);
+
+ ret = pthread_create(&thread, 0, racer, addr_gva2hva(vm, (vm_vaddr_t)&race_op));
+ TEST_ASSERT(ret == 0, "pthread_create() failed: %s", strerror(ret));
+
+ do {
+ vcpu_run(vm, VCPU_ID);
+ get_ucall(vm, VCPU_ID, &uc);
+ } while (check_state(run, &uc));
+
+ ret = pthread_cancel(thread);
+ TEST_ASSERT(ret == 0, "pthread_cancel() failed: %s", strerror(ret));
+
+ ret = pthread_join(thread, 0);
+ TEST_ASSERT(ret == 0, "pthread_join() failed: %s", strerror(ret));
+
+ kvm_vm_free(vm);
+ return 0;
+}
--
2.32.0
