THREAD 92bdc4f8 Cid 06f0.0304 Teb: 7ffd6000 Win32Thread: fd9ffa90 WAIT: (WrLpcReply) UserMode Non-Alertable
92bdc72c Semaphore Limit 0x1
Waiting for reply to ALPC Message a1ec8b00 : queued at port 92b54f00 : owned by process 8c93d820
Not impersonating
DeviceMap 8c628e68
Owning Process 92af1738 Image: XXX.exe
Attached Process N/A Image: N/A
Wait Start TickCount 9884 Ticks: 13579 (0:00:03:31.833)
Context Switch Count 1079 IdealProcessor: 0
UserTime 00:00:00.109
KernelTime 00:00:00.156
Win32 Start Address 0x6d5842c8
Stack Init 97af9ed0 Current 97af9828 Base 97afa000 Limit 97af7000 Call 0
Priority 9 BasePriority 8 UnusualBoost 0 ForegroundBoost 0 IoPriority 2 PagePriority 5
ChildEBP RetAddr
97af9840 8408069d nt!KiSwapContext+0x26 (FPO: [Uses EBP] [0,0,4])
97af9878 8407f4c7 nt!KiSwapThread+0x266
97af98a0 840790cf nt!KiCommitThreadWait+0x1df
97af991c 840b0e75 nt!KeWaitForSingleObject+0x393
97af9944 8423e4dc nt!AlpcpSignalAndWait+0x7b
97af9968 8425fca6 nt!AlpcpReceiveSynchronousReply+0x27
97af99f8 8425514e nt!AlpcpProcessSynchronousRequest+0x276
97af9a60 8c4427b8 nt!NtAlpcSendWaitReceivePort+0xd0
这个堆栈很明显卡在LPC里面了，这个线程在等待回复，可是老是没有人回复它然后就一直卡在那里了。我们可以先通过 NtAlpcSendWaitReceivePort看下里面的参数找些有用的信息，该函数的原型如下
NTSYSCALLAPI
NTSTATUS
NTAPI
ZwAlpcSendWaitReceivePort(
__in HANDLE PortHandle,
__in ULONG Flags,
__in_opt PPORT_MESSAGE SendMessage,
__in_opt PALPC_MESSAGE_ATTRIBUTES SendMessageAttributes,
__inout_opt PPORT_MESSAGE ReceiveMessage,
__inout_opt PULONG BufferLength,
__inout_opt PALPC_MESSAGE_ATTRIBUTES ReceiveMessageAttributes,
__in_opt PLARGE_INTEGER Timeout
);
我们先获取下这个函数的参数
kd> dd 97af9a60 +8 L8
97af9a68 000003b8 00020000 0c7c3fd0 06b8cef4
kd> !handle 3b8
PROCESS 92a3a988 SessionId: 0 Cid: 05d4 Peb: 7ffdf000 ParentCid: 0230
DirBase: 3e8a8380 ObjectTable: 9468f140 HandleCount: 1261.
Image: AvastSvc.exe
Handle table at 9468f140 with 1261 entries in use
03b8: Object: a31ed180 GrantedAccess: 00120089 Entry: 9468c770
Object: a31ed180 Type: (869e3eb0) File
ObjectHeader: a31ed168 (new version)
HandleCount: 10 PointerCount: 10
Directory Object: 00000000 Name: \Program Files\AVAST Software\Avast\defs\14010700\db_evope.dat {HarddiskVolume2}
这个句柄是AvastSvc.exe这个进程的。好了我们看下LPC的消息处理的服务线程是谁
kd> !alpc /m a1ec8b00
Message a1ec8b00
MessageID : 0x0828 (2088)
CallbackID : 0x1CCEB (117995)
SequenceNumber : 0x00000002 (2)
Type : LPC_REQUEST
DataLength : 0x0064 (100)
TotalLength : 0x007C (124)
Canceled : No
Release : No
ReplyWaitReply : No
Continuation : Yes
OwnerPort : 87485918 [ALPC_CLIENT_COMMUNICATION_PORT]
WaitingThread : 92bdc4f8
QueueType : ALPC_MSGQUEUE_PENDING
QueuePort : 92b54f00 [ALPC_CONNECTION_PORT]
QueuePortOwnerProcess : 8c93d820 (svchost.exe)
ServerThread : 8b3f3470
QuotaCharged : No
CancelQueuePort : 00000000
CancelSequencePort : 00000000
CancelSequenceNumber : 0x00000000 (0)
ClientContext : 06b8ce40
ServerContext : 00000000
PortContext : 00fc00c8
CancelPortContext : 00000000
SecurityData : 00000000
View : 00000000
HandleData : 00000000
kd> !thread 8b3f3470
THREAD 8b3f3470 Cid 0190.0abc Teb: 7ff8e000 Win32Thread: 00000000 WAIT: (UserRequest) UserMode Non-Alertable
92bd4d00 NotificationEvent
9685e090 Mutant - owning thread 88a5ad48
Not impersonating
DeviceMap 8b67ab10
Owning Process 8c93d820 Image: svchost.exe
Attached Process N/A Image: N/A
Wait Start TickCount 9915 Ticks: 13548 (0:00:03:31.350)
Context Switch Count 23 IdealProcessor: 0
UserTime 00:00:00.000
KernelTime 00:00:00.000
Win32 Start Address ntdll!TppWorkerThread (0x770903e7)
Stack Init a58efed0 Current a58ef648 Base a58f0000 Limit a58ed000 Call 0
Priority 8 BasePriority 8 UnusualBoost 0 ForegroundBoost 0 IoPriority 2 PagePriority 5
ChildEBP RetAddr Args to Child
a58ef660 8408069d 8b3f3470 00000000 8412cd20 nt!KiSwapContext+0x26 (FPO: [Uses EBP] [0,0,4])
a58ef698 8407f4c7 9685e090 8b3f3470 8b3f356c nt!KiSwapThread+0x266
a58ef6c0 8407b4a4 8b3f3470 8b3f3530 00000000 nt!KiCommitThreadWait+0x1df
a58ef83c 8422b8c0 00000002 a58ef974 00000001 nt!KeWaitForMultipleObjects+0x535
a58efac8 8422b62d 00000002 a58efafc 00000001 nt!ObpWaitForMultipleObjects+0x262
a58efc18 8404028a 00000002 0222f04c 00000001 nt!NtWaitForMultipleObjects+0xcd
a58efc18 770a70b4 00000002 0222f04c 00000001 nt!KiFastCallEntry+0x12a (FPO: [0,3] TrapFrame @ a58efc34)
0222f098 00000000 00000000 00000000 00000000 ntdll!KiFastSystemCallRet (FPO: [0,0,0])
我们可以看到这个服务线程在svchost.exe里面，此时它正在处理消息，但是没有回复我们的请求，我们注意看WAIT: (UserRequest) 这里，正常情况下如果这个线程回复我们的话应该是WAIT: (WrLpcReceive)所以像这种UserRequest的话，一般是由critical section（临界区)或者synchronization object(同步对象)在等待其他线程 。因此我们可以看下这些同步对象或临界区是谁的
kd> dt _KMUTANT 9685e090
nt!_KMUTANT
+0x000 Header : _DISPATCHER_HEADER
+0x010 MutantListEntry : _LIST_ENTRY [ 0x88a5af30 - 0x88a5af30 ]
+0x018 OwnerThread : 0x88a5ad48 _KTHREAD
+0x01c Abandoned : 0 ''
kd> !thread 0x88a5ad48
THREAD 88a5ad48 Cid 0190.0ac0 Teb: 7ff90000 Win32Thread: 00000000 WAIT: (WrLpcReply) UserMode Non-Alertable
88a5af7c Semaphore Limit 0x1
Waiting for reply to ALPC Message a1e498e0 : queued at port 92b54f00 : owned by process 8c93d820
Not impersonating
DeviceMap 8b67ab10
Owning Process 8c93d820 Image: svchost.exe
Attached Process N/A Image: N/A
Wait Start TickCount 20756 Ticks: 2707 (0:00:00:42.229)
Context Switch Count 51 IdealProcessor: 0
UserTime 00:00:00.000
KernelTime 00:00:00.000
Win32 Start Address ntdll!TppWorkerThread (0x770903e7)
Stack Init a58e7ed0 Current a58e7828 Base a58e8000 Limit a58e5000 Call 0
Priority 9 BasePriority 8 UnusualBoost 0 ForegroundBoost 0 IoPriority 2 PagePriority 5
ChildEBP RetAddr Args to Child
a58e7840 8408069d 88a5ad48 00000000 8412cd20 nt!KiSwapContext+0x26 (FPO: [Uses EBP] [0,0,4])
a58e7878 8407f4c7 88a5ae08 88a5ad48 88a5af7c nt!KiSwapThread+0x266
a58e78a0 840790cf 88a5ad48 88a5ae08 00000000 nt!KiCommitThreadWait+0x1df
a58e791c 840b0e75 88a5af7c 00000011 8c930001 nt!KeWaitForSingleObject+0x393
a58e7944 8423e4dc 88a5af7c 8c930001 00000000 nt!AlpcpSignalAndWait+0x7b
a58e7968 8425fca6 8c930001 a58e79d4 60000000 nt!AlpcpReceiveSynchronousReply+0x27
a58e79f8 8425514e 8c8f4f00 00020000 00ff37a8 nt!AlpcpProcessSynchronousRequest+0x276
a58e7a60 8c4427b8 00000200 00020000 00ff37a8 nt!NtAlpcSendWaitReceivePort+0xd0
同样的我们看到这个拥有MUTANT对象的线程里面也在等另一个LPC的回应，同样的我们可以看下这里的 NtAlpcSendWaitReceivePort句柄是谁的
kd> dd a58e7a60+8 L8
a58e7a68 00000200 00020000 00ff37a8 001ad21c
a58e7a78 00ff37a8 0227f468 001ad21c 00000000
kd> !handle 00000200
PROCESS 92a3a988 SessionId: 0 Cid: 05d4 Peb: 7ffdf000 ParentCid: 0230
DirBase: 3e8a8380 ObjectTable: 9468f140 HandleCount: 1261.
Image: AvastSvc.exe
Handle table at 9468f140 with 1261 entries in use
0200: Object: 8b3ac728 GrantedAccess: 00100081 Entry: 9468c400
Object: 8b3ac728 Type: (869e3eb0) File
ObjectHeader: 8b3ac710 (new version)
HandleCount: 1 PointerCount: 2
kd> !alpc /m a1e498e0
Message a1e498e0
MessageID : 0x07E0 (2016)
CallbackID : 0x25537 (152887)
SequenceNumber : 0x00000026 (38)
Type : LPC_REQUEST
DataLength : 0x0058 (88)
TotalLength : 0x0070 (112)
Canceled : No
Release : No
ReplyWaitReply : No
Continuation : Yes
OwnerPort : 8c8f4f00 [ALPC_CLIENT_COMMUNICATION_PORT]
WaitingThread : 88a5ad48
QueueType : ALPC_MSGQUEUE_PENDING
QueuePort : 92b54f00 [ALPC_CONNECTION_PORT]
QueuePortOwnerProcess : 8c93d820 (svchost.exe)
ServerThread : 92ac8718
QuotaCharged : No
CancelQueuePort : 00000000
CancelSequencePort : 00000000
CancelSequenceNumber : 0x00000000 (0)
ClientContext : 001ad168
ServerContext : 00000000
PortContext : 001ad028
CancelPortContext : 00000000
SecurityData : 00000000
View : 00000000
kd> !thread 92ac8718
THREAD 92ac8718 Cid 0190.11c0 Teb: 7ff82000 Win32Thread: 00000000 WAIT: (UserRequest) UserMode Non-Alertable
885c1f00 Semaphore Limit 0x1
Not impersonating
DeviceMap 8b67ab10
Owning Process 8c93d820 Image: svchost.exe
Attached Process N/A Image: N/A
Wait Start TickCount 21361 Ticks: 2102 (0:00:00:32.791)
Context Switch Count 37 IdealProcessor: 0
UserTime 00:00:00.000
KernelTime 00:00:00.000
Win32 Start Address ntdll!TppWorkerThread (0x770903e7)
Stack Init a68c3ed0 Current a68c3ac8 Base a68c4000 Limit a68c1000 Call 0
Priority 8 BasePriority 8 UnusualBoost 0 ForegroundBoost 0 IoPriority 2 PagePriority 5
ChildEBP RetAddr Args to Child
a68c3ae0 8408069d 92ac8718 00000000 8412cd20 nt!KiSwapContext+0x26 (FPO: [Uses EBP] [0,0,4])
a68c3b18 8407f4c7 92ac87d8 92ac8718 885c1f00 nt!KiSwapThread+0x266
a68c3b40 840790cf 92ac8718 92ac87d8 000000a0 nt!KiCommitThreadWait+0x1df
a68c3bb8 8422acd7 885c1f00 00000006 84080d01 nt!KeWaitForSingleObject+0x393
a68c3c20 8404028a 000000e4 00000000 a68c3be4 nt!NtWaitForSingleObject+0xc6
a68c3c20 770a70b4 000000e4 00000000 a68c3be4 nt!KiFastCallEntry+0x12a (FPO: [0,3] TrapFrame @ a68c3c34)
0285f240 00000000 00000000 00000000 00000000 ntdll!KiFastSystemCallRet (FPO: [0,0,0])
同样这个服务线程也在等待消息处理。在这里我们就得不到其它有用的信息了，此时我在想为什么这个svchost.exe没有回复LPC的请求。要想知道为什么svchost.exe没有回应请求那我们就需要看下这个svchost.exe的所有线程是不是有其他可疑的地方直接!process 8c93d820 ，接着就是找出可疑的线程看下
THREAD 96877288 Cid 0190.06b8 Teb: 7ffda000 Win32Thread: 00000000 WAIT: (UserRequest) UserMode Non-Alertable
96875428 SynchronizationEvent
968761c8 NotificationEvent
87666fb0 NotificationEvent
96876188 NotificationEvent
87666ff0 NotificationEvent
IRP List:
889cd560: (0006,0094) Flags: 00060070 Mdl: 00000000
92bc9a00: (0006,0094) Flags: 00060070 Mdl: 00000000
885be9d8: (0006,0094) Flags: 00060070 Mdl: 00000000
92b11bf8: (0006,0094) Flags: 00060070 Mdl: 00000000
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