Avoid undefined behavior: member access within misaligned address

Before this change we see the following UBSAN stack trace in Fuchsia:

  #0    0x00002132da6299a1 in AcpiUtValidateResource(ACPI_WALK_STATE*, void*, UINT8*) ../../third_party/acpica/source/components/utilities/utresrc.c:426 <platform-bus-x86.so>+0x2f79a1
  #1.2  0x000023e6cd58577f in ubsan_GetStackTrace() compiler-rt/lib/ubsan/ubsan_diag.cpp:41 <libclang_rt.asan.so>+0x3d77f
  #1.1  0x000023e6cd58577f in MaybePrintStackTrace() compiler-rt/lib/ubsan/ubsan_diag.cpp:51 <libclang_rt.asan.so>+0x3d77f
  #1    0x000023e6cd58577f in ~ScopedReport() compiler-rt/lib/ubsan/ubsan_diag.cpp:387 <libclang_rt.asan.so>+0x3d77f
  #2    0x000023e6cd586385 in handleTypeMismatchImpl() compiler-rt/lib/ubsan/ubsan_handlers.cpp:137 <libclang_rt.asan.so>+0x3e385
  #3    0x000023e6cd585ead in compiler-rt/lib/ubsan/ubsan_handlers.cpp:142 <libclang_rt.asan.so>+0x3dead
  #4    0x00002132da6299a1 in AcpiUtValidateResource(ACPI_WALK_STATE*, void*, UINT8*) ../../third_party/acpica/source/components/utilities/utresrc.c:426 <platform-bus-x86.so>+0x2f79a1
  #5    0x00002132da628ffe in AcpiUtWalkAmlResources(ACPI_WALK_STATE*, UINT8*, ACPI_SIZE, ACPI_WALK_AML_CALLBACK, void**) ../../third_party/acpica/source/components/utilities/utresrc.c:216 <platform-bus-x86.so>+0x2f6ffe
  #6    0x00002132da5b2405 in AcpiExConcatTemplate(ACPI_OPERAND_OBJECT*, ACPI_OPERAND_OBJECT*, ACPI_OPERAND_OBJECT**, ACPI_WALK_STATE*) ../../third_party/acpica/source/components/executer/exconcat.c:414 <platform-bus-x86.so>+0x280405
  #7    0x00002132da5ad5a4 in AcpiExOpcode_2A_1T_1R(ACPI_WALK_STATE*) ../../third_party/acpica/source/components/executer/exoparg2.c:383 <platform-bus-x86.so>+0x27b5a4
  #8    0x00002132da57ee7d in AcpiDsExecEndOp(ACPI_WALK_STATE*) ../../third_party/acpica/source/components/dispatcher/dswexec.c:482 <platform-bus-x86.so>+0x24ce7d
  #9    0x00002132da5ed196 in AcpiPsParseLoop(ACPI_WALK_STATE*) ../../third_party/acpica/source/components/parser/psloop.c:554 <platform-bus-x86.so>+0x2bb196
  #10   0x00002132da5ea458 in AcpiPsParseAml(ACPI_WALK_STATE*) ../../third_party/acpica/source/components/parser/psparse.c:525 <platform-bus-x86.so>+0x2b8458
  #11   0x00002132da5f8a92 in AcpiPsExecuteMethod(ACPI_EVALUATE_INFO*) ../../third_party/acpica/source/components/parser/psxface.c:244 <platform-bus-x86.so>+0x2c6a92
  #12   0x00002132da55c2b2 in AcpiNsEvaluate(ACPI_EVALUATE_INFO*) ../../third_party/acpica/source/components/namespace/nseval.c:250 <platform-bus-x86.so>+0x22a2b2
  #13   0x00002132da61fd45 in AcpiUtEvaluateObject(ACPI_NAMESPACE_NODE*, const char*, UINT32, ACPI_OPERAND_OBJECT**) ../../third_party/acpica/source/components/utilities/uteval.c:100 <platform-bus-x86.so>+0x2edd45
  #14   0x00002132da606197 in AcpiRsGetMethodData(ACPI_HANDLE, const char*, ACPI_BUFFER*) ../../third_party/acpica/source/components/resources/rsutils.c:757 <platform-bus-x86.so>+0x2d4197
  #15   0x00002132da60652d in AcpiWalkResources(ACPI_HANDLE, char*, ACPI_WALK_RESOURCE_CALLBACK, void*) ../../third_party/acpica/source/components/resources/rsxface.c:731 <platform-bus-x86.so>+0x2d452d
  #16   0x00002132da41dd48 in acpi::AcpiImpl::WalkResources(acpi::AcpiImpl*, ACPI_HANDLE, const char*, acpi::Acpi::ResourcesCallable) ../../src/devices/board/lib/acpi/acpi-impl.cc:41 <platform-bus-x86.so>+0xebd48
  #17   0x00002132da42394d in acpi::DeviceBuilder::GatherResources(acpi::DeviceBuilder*, acpi::Acpi*, fidl::AnyArena&, acpi::Manager*, acpi::DeviceBuilder::GatherResourcesCallback) ../../src/devices/board/lib/acpi/device-builder.cc:52 <platform-bus-x86.so>+0xf194d
  #18   0x00002132da4afaf2 in acpi::Manager::ConfigureDiscoveredDevices(acpi::Manager*) ../../src/devices/board/lib/acpi/manager.cc:75 <platform-bus-x86.so>+0x17daf2
  #19   0x00002132da3d7b44 in publish_acpi_devices(acpi::Manager*, zx_device_t*, zx_device_t*) ../../src/devices/board/drivers/x86/acpi-nswalk.cc:102 <platform-bus-x86.so>+0xa5b44
  #20   0x00002132da3e96f7 in x86::X86::DoInit(x86::X86*) ../../src/devices/board/drivers/x86/x86.cc:65 <platform-bus-x86.so>+0xb76f7
  #21.1 0x00002132da3f38ea in λ(x86::X86::DdkInit::(anon class)*) ../../src/devices/board/drivers/x86/x86.cc:82 <platform-bus-x86.so>+0xc18ea
  #21   0x00002132da3f38ea in fit::internal::target<(lambda at../../src/devices/board/drivers/x86/x86.cc:81:19), false, false, void>::invoke(void*) ../../sdk/lib/fit/include/lib/fit/internal/function.h:181 <platform-bus-x86.so>+0xc18ea
  #22.2 0x00002132da638c6c in fit::internal::function_base<16UL, false, void()>::invoke(const fit::internal::function_base<16UL, false, void ()>*) ../../sdk/lib/fit/include/lib/fit/internal/function.h:505 <platform-bus-x86.so>+0x306c6c
  #22.1 0x00002132da638c6c in fit::function_impl<16UL, false, void()>::operator()(const fit::function_impl<16UL, false, void ()>*) ../../sdk/lib/fit/include/lib/fit/function.h:300 <platform-bus-x86.so>+0x306c6c
  #22   0x00002132da638c6c in async::internal::RetainedTask::Handler(async_dispatcher_t*, async_task_t*, zx_status_t) ../../zircon/system/ulib/async/task.cc:25 <platform-bus-x86.so>+0x306c6c
  #23.1 0x000022c67b305d91 in λ(const driver_runtime::Dispatcher::PostTask::(anon class)*, std::__2::unique_ptr<driver_runtime::CallbackRequest, std::__2::default_delete<driver_runtime::CallbackRequest> >, zx_status_t) ../../src/devices/bin/driver_runtime/dispatcher.cc:715 <libdriver_runtime.so>+0x4bd91
  #23   0x000022c67b305d91 in fit::internal::target<(lambda at../../src/devices/bin/driver_runtime/dispatcher.cc:714:7), true, false, void, std::__2::unique_ptr<driver_runtime::CallbackRequest, std::__2::default_delete<driver_runtime::CallbackRequest>>, int>::invoke(void*, std::__2::unique_ptr<driver_runtime::CallbackRequest, std::__2::default_delete<driver_runtime::CallbackRequest> >, int) ../../sdk/lib/fit/include/lib/fit/internal/function.h:128 <libdriver_runtime.so>+0x4bd91
  #24   0x000022c67b2febc9 in fit::internal::function_base<24UL, true, void(std::__2::unique_ptr<driver_runtime::CallbackRequest, std::__2::default_delete<driver_runtime::CallbackRequest>>, int)>::invoke(const fit::internal::function_base<24UL, true, void (std::__2::unique_ptr<driver_runtime::CallbackRequest, std::__2::default_delete<driver_runtime::CallbackRequest> >, int)>*, std::__2::unique_ptr<driver_runtime::CallbackRequest, std::__2::default_delete<driver_runtime::CallbackRequest> >, int) ../../sdk/lib/fit/include/lib/fit/internal/function.h:505 <libdriver_runtime.so>+0x44bc9
  #25   0x000022c67b2fe8dd in fit::callback_impl<24UL, true, void(std::__2::unique_ptr<driver_runtime::CallbackRequest, std::__2::default_delete<driver_runtime::CallbackRequest>>, int)>::operator()(fit::callback_impl<24UL, true, void (std::__2::unique_ptr<driver_runtime::CallbackRequest, std::__2::default_delete<driver_runtime::CallbackRequest> >, int)>*, std::__2::unique_ptr<driver_runtime::CallbackRequest, std::__2::default_delete<driver_runtime::CallbackRequest> >, int) ../../sdk/lib/fit/include/lib/fit/function.h:451 <libdriver_runtime.so>+0x448dd
  #26   0x000022c67b2ef6a6 in driver_runtime::CallbackRequest::Call(driver_runtime::CallbackRequest*, std::__2::unique_ptr<driver_runtime::CallbackRequest, std::__2::default_delete<driver_runtime::CallbackRequest> >, zx_status_t) ../../src/devices/bin/driver_runtime/callback_request.h:67 <libdriver_runtime.so>+0x356a6
  #27   0x000022c67b2f64c8 in driver_runtime::Dispatcher::DispatchCallback(driver_runtime::Dispatcher*, std::__2::unique_ptr<driver_runtime::CallbackRequest, std::__2::default_delete<driver_runtime::CallbackRequest> >) ../../src/devices/bin/driver_runtime/dispatcher.cc:1093 <libdriver_runtime.so>+0x3c4c8
  #28   0x000022c67b2f72c1 in driver_runtime::Dispatcher::DispatchCallbacks(driver_runtime::Dispatcher*, std::__2::unique_ptr<driver_runtime::Dispatcher::EventWaiter, std::__2::default_delete<driver_runtime::Dispatcher::EventWaiter> >, fbl::RefPtr<driver_runtime::Dispatcher>) ../../src/devices/bin/driver_runtime/dispatcher.cc:1169 <libdriver_runtime.so>+0x3d2c1
  #29.1 0x000022c67b30281e in λ(std::__2::unique_ptr<driver_runtime::Dispatcher::EventWaiter, std::__2::default_delete<driver_runtime::Dispatcher::EventWaiter> >, fbl::RefPtr<driver_runtime::Dispatcher>, const driver_runtime::Dispatcher::CreateWithAdder::(anon class)*) ../../src/devices/bin/driver_runtime/dispatcher.cc:338 <libdriver_runtime.so>+0x4881e
  #29   0x000022c67b30281e in fit::internal::target<(lambda at../../src/devices/bin/driver_runtime/dispatcher.cc:337:7), true, false, void, std::__2::unique_ptr<driver_runtime::Dispatcher::EventWaiter, std::__2::default_delete<driver_runtime::Dispatcher::EventWaiter>>, fbl::RefPtr<driver_runtime::Dispatcher>>::invoke(void*, std::__2::unique_ptr<driver_runtime::Dispatcher::EventWaiter, std::__2::default_delete<driver_runtime::Dispatcher::EventWaiter> >, fbl::RefPtr<driver_runtime::Dispatcher>) ../../sdk/lib/fit/include/lib/fit/internal/function.h:128 <libdriver_runtime.so>+0x4881e
  #30   0x000022c67b2fee7e in fit::internal::function_base<8UL, true, void(std::__2::unique_ptr<driver_runtime::Dispatcher::EventWaiter, std::__2::default_delete<driver_runtime::Dispatcher::EventWaiter>>, fbl::RefPtr<driver_runtime::Dispatcher>)>::invoke(const fit::internal::function_base<8UL, true, void (std::__2::unique_ptr<driver_runtime::Dispatcher::EventWaiter, std::__2::default_delete<driver_runtime::Dispatcher::EventWaiter> >, fbl::RefPtr<driver_runtime::Dispatcher>)>*, std::__2::unique_ptr<driver_runtime::Dispatcher::EventWaiter, std::__2::default_delete<driver_runtime::Dispatcher::EventWaiter> >, fbl::RefPtr<driver_runtime::Dispatcher>) ../../sdk/lib/fit/include/lib/fit/internal/function.h:505 <libdriver_runtime.so>+0x44e7e
  #31.1 0x000022c67b2f8964 in fit::function_impl<8UL, true, void(std::__2::unique_ptr<driver_runtime::Dispatcher::EventWaiter, std::__2::default_delete<driver_runtime::Dispatcher::EventWaiter>>, fbl::RefPtr<driver_runtime::Dispatcher>)>::operator()(const fit::function_impl<8UL, true, void (std::__2::unique_ptr<driver_runtime::Dispatcher::EventWaiter, std::__2::default_delete<driver_runtime::Dispatcher::EventWaiter> >, fbl::RefPtr<driver_runtime::Dispatcher>)>*, std::__2::unique_ptr<driver_runtime::Dispatcher::EventWaiter, std::__2::default_delete<driver_runtime::Dispatcher::EventWaiter> >, fbl::RefPtr<driver_runtime::Dispatcher>) ../../sdk/lib/fit/include/lib/fit/function.h:300 <libdriver_runtime.so>+0x3e964
  #31   0x000022c67b2f8964 in driver_runtime::Dispatcher::EventWaiter::InvokeCallback(driver_runtime::Dispatcher::EventWaiter*, std::__2::unique_ptr<driver_runtime::Dispatcher::EventWaiter, std::__2::default_delete<driver_runtime::Dispatcher::EventWaiter> >, fbl::RefPtr<driver_runtime::Dispatcher>) ../../src/devices/bin/driver_runtime/dispatcher.h:299 <libdriver_runtime.so>+0x3e964
  #32   0x000022c67b2f835d in driver_runtime::Dispatcher::EventWaiter::HandleEvent(std::__2::unique_ptr<driver_runtime::Dispatcher::EventWaiter, std::__2::default_delete<driver_runtime::Dispatcher::EventWaiter> >, async_dispatcher_t*, async::WaitBase*, zx_status_t, zx_packet_signal_t const*) ../../src/devices/bin/driver_runtime/dispatcher.cc:1259 <libdriver_runtime.so>+0x3e35d
  #33.1 0x000022c67b302c00 in AsyncLoopOwnedEventHandler<driver_runtime::Dispatcher::EventWaiter>::HandleEvent(AsyncLoopOwnedEventHandler<driver_runtime::Dispatcher::EventWaiter>*, zx_status_t, zx_packet_signal_t const*, async_dispatcher_t*, async::WaitBase*) ../../src/devices/bin/driver_runtime/async_loop_owned_event_handler.h:59 <libdriver_runtime.so>+0x48c00
  #33   0x000022c67b302c00 in async::WaitMethod<AsyncLoopOwnedEventHandler<driver_runtime::Dispatcher::EventWaiter>, &AsyncLoopOwnedEventHandler<driver_runtime::Dispatcher::EventWaiter>::HandleEvent>::CallHandler(async_dispatcher_t*, async_wait_t*, zx_status_t, zx_packet_signal_t const*) ../../zircon/system/ulib/async/include/lib/async/cpp/wait.h:201 <libdriver_runtime.so>+0x48c00
  #34.1 0x000022c67b324ead in async_loop_run_once(async_loop_t*, zx_time_t) ../../zircon/system/ulib/async-loop/loop.c:415 <libdriver_runtime.so>+0x6aead
  #34   0x000022c67b324ead in async_loop_run(async_loop_t*, zx_time_t, _Bool) ../../zircon/system/ulib/async-loop/loop.c:288 <libdriver_runtime.so>+0x6aead
  #35   0x000022c67b32678f in async_loop_run_thread(void*) ../../zircon/system/ulib/async-loop/loop.c:840 <libdriver_runtime.so>+0x6c78f
  #36   0x0000431cc3246edc in start_c11(void*) ../../zircon/third_party/ulib/musl/pthread/pthread_create.c:55 <libc.so>+0xd7edc
  #37   0x0000431cc337796d in thread_trampoline(uintptr_t, uintptr_t) ../../zircon/system/ulib/runtime/thread.cc:100 <libc.so>+0x20896d

1 files changed, 8 insertions, 3 deletions

diff --git a/source/components/utilities/utresrc.c b/source/components/utilities/utresrc.c
index 7898e9929..f47b29246 100644
--- a/source/components/utilities/utresrc.c
+++ b/source/components/utilities/utresrc.c
@@ -532,16 +532,21 @@ AcpiUtValidateResource (
     AmlResource = ACPI_CAST_PTR (AML_RESOURCE, Aml);
     if (ResourceType == ACPI_RESOURCE_NAME_SERIAL_BUS)
     {
+        /* Avoid undefined behavior: member access within misaligned address */
+
+        AML_RESOURCE_COMMON_SERIALBUS CommonSerialBus;
+        memcpy(&CommonSerialBus, AmlResource, sizeof(CommonSerialBus));
+
         /* Validate the BusType field */
 
-        if ((AmlResource->CommonSerialBus.Type == 0) ||
-            (AmlResource->CommonSerialBus.Type > AML_RESOURCE_MAX_SERIALBUSTYPE))
+        if ((CommonSerialBus.Type == 0) ||
+            (CommonSerialBus.Type > AML_RESOURCE_MAX_SERIALBUSTYPE))
         {
             if (WalkState)
             {
                 ACPI_ERROR ((AE_INFO,
                     "Invalid/unsupported SerialBus resource descriptor: BusType 0x%2.2X",
-                    AmlResource->CommonSerialBus.Type));
+                    CommonSerialBus.Type));
             }
             return (AE_AML_INVALID_RESOURCE_TYPE);
         }