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Please check out the Community Guidelines in the Announcements and Administration Category.Upper filter driver waitlock
I wrote an upper filter driver and on the PASSIVE_LEVEL I use
WdfWaitLockAcquire(driverData->lockHandle, NULL);
that no second access is possible. What must I do, if I want to lock/access the same code from dispatch_level (ServiceCallback)?
I tried Waitlock and Spinlock but always get a bugcheck.
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Comments
Bent from my phone
________________________________
From: Mak
Sent: Saturday, November 3, 2018 8:12:45 AM
To: Doron Holan
Subject: [NTDEV] Upper filter driver waitlock
OSR https://na01.safelinks.protection.outlook.com/?url=https://community.osr.com/&data=02|01|[email protected]|671d9d1508c54aa62a2308d6419ecfef|72f988bf86f141af91ab2d7cd011db47|1|0|636768547706168845&sdata=u8KiAUr1QX55lxXs8n1pE01KeMhYGWWbqwwEvuy1k9Y=&reserved=0
Mak started a new discussion: Upper filter driver waitlock
I wrote an upper filter driver and on the PASSIVE_LEVEL I use
> WdfWaitLockAcquire(driverData->lockHandle, NULL);
that no second access is possible. What must I do, if I want to lock/access the same code from dispatch_level (ServiceCallback)?
I tried Waitlock and Spinlock but always get a bugcheck.
You must always use the spin lock -- You have to use the same lock to guard a given block of data. If that data is never accessed at IRQL DISPATCH_LEVEL or above, you use a mutex. If that data is ever in any data path accessed at IRQL DISPATCH_LEVEL, then you must use a Spin Lock (prior to accessing the data at any IRQL, even at IRQL PASSIVE_LEVEL). The IRQL associated with a locking primitive indicates the maximum IRQL at which the lock may be obtained.
Peter
Peter Viscarola
OSR
@OSRDrivers
Thanks. It works now.
One question left:
I communicate with the user land via Inverted call with a ring buffer. In this scenario I have two functions. One is called inside the driver to place the data in the queue and the second is if the call comes from the user land with IOCTL to get the data. I have now set a Spin Lock in this two functions. Is this correct? I have no problem with the inverted call without Spin Lock. I only want to know if this is necessary to make the code save.
d
Bent from my phone
________________________________
From: Mak
Sent: Sunday, November 4, 2018 1:53:34 AM
To: Doron Holan
Subject: Re: [NTDEV] Upper filter driver waitlock
OSR https://na01.safelinks.protection.outlook.com/?url=https://community.osr.com/&data=02|01|[email protected]|10bf15aeabac45d569ae08d6423301c5|72f988bf86f141af91ab2d7cd011db47|1|0|636769184188358590&sdata=O+YVBRBA1o5HAGkU/US6UrEW8V3liLEE+G1qWJFagVg=&reserved=0
Mak commented on Upper filter driver waitlock
Thanks. It works now.
One question left:
I communicate with the user land via Inverted call with a ring buffer. In this scenario I have two functions. One is called inside the driver to place the data in the queue and the second is if the call comes from the user land with IOCTL to get the data. I have now set a Spin Lock in this two functions. Is this correct? I have no problem with the inverted call without Spin Lock. I only want to know if this is necessary to make the code save.
We really can't tell you that, without seeing all your code (and, no, that is not an invitation to post it here). In general, any time you share data between multiple separate threads of processing, you need a lock to ensure that both threads don't attempt to update the same data data at the same time. For example, you don't want one routine trying to put something ON a list, while at the same time you have another routine trying to take something OFF that same list. If the timing is "unlucky", the two threads can interfere with each other, right? So, each thread takes out a lock before manipulating the shared data (the list, in the example I just cited)... THEN does the manipulation (insert or remove from the list, for example)... and then releases the lock. The lock ensures that the manipulation of the shared data is done without the other thread of processing interfering, that is it ensures the manipulation is done "atomically."
This is a general precept of how one makes things thread-safe. It's not a driver specific thing. Though the TYPES of locks you can use (wait or spin) are definitely specific to the world of drivers.
Hope that helps,
Peter
Peter Viscarola
OSR
@OSRDrivers
Peter, I am a developer on the user land since many years and I know for what we need locks. The problem is that I have not so much knowledge how in general the concept in the driver land are. Sometimes it can be unnecessary to use locks because the system serialize the things. This was the reason for my question.
Doron answered my question already very well.
Since I use the locks I get the following bugcheck and have no idea where I must look in the code:
Loading unloaded module list
........Unable to enumerate user-mode unloaded modules, Win32 error 0n30
Use !analyze -v to get detailed debugging information.
BugCheck 7E, {ffffffffc0000005, fffff801fbd24c7b, ffff970dc858e598, ffff970dc858dde0}
*** ERROR: Module load completed but symbols could not be loaded for Ch64USB.sys
Probably caused by : Ch64USB.sys ( Ch64USB+14c7b )
Followup: MachineOwner
nt!DbgBreakPointWithStatus:
fffff800`f68598d0 cc int 3
0: kd> !analyze -v
SYSTEM_THREAD_EXCEPTION_NOT_HANDLED (7e)
This is a very common bugcheck. Usually the exception address pinpoints
the driver/function that caused the problem. Always note this address
as well as the link date of the driver/image that contains this address.
Arguments:
Arg1: ffffffffc0000005, The exception code that was not handled
Arg2: fffff801fbd24c7b, The address that the exception occurred at
Arg3: ffff970dc858e598, Exception Record Address
Arg4: ffff970dc858dde0, Context Record Address
Debugging Details:
KEY_VALUES_STRING: 1
STACKHASH_ANALYSIS: 1
TIMELINE_ANALYSIS: 1
DUMP_CLASS: 1
DUMP_QUALIFIER: 0
BUILD_VERSION_STRING: 17134.1.amd64fre.rs4_release.180410-1804
DUMP_TYPE: 0
BUGCHECK_P1: ffffffffc0000005
BUGCHECK_P2: fffff801fbd24c7b
BUGCHECK_P3: ffff970dc858e598
BUGCHECK_P4: ffff970dc858dde0
EXCEPTION_CODE: (NTSTATUS) 0xc0000005 - The instruction at 0x%p referenced memory at 0x%p. The memory could not be %s.
FAULTING_IP:
Ch64USB+14c7b
fffff801`fbd24c7b 0fb616 movzx edx,byte ptr [rsi]
EXCEPTION_RECORD: ffff970dc858e598 -- (.exr 0xffff970dc858e598)
ExceptionAddress: fffff801fbd24c7b (Ch64USB+0x0000000000014c7b)
ExceptionCode: c0000005 (Access violation)
ExceptionFlags: 00000000
NumberParameters: 2
Parameter[0]: 0000000000000000
Parameter[1]: 00000000b02e6a50
Attempt to read from address 00000000b02e6a50
CONTEXT: ffff970dc858dde0 -- (.cxr 0xffff970dc858dde0)
rax=ffffd98db0e46030 rbx=0000000000000001 rcx=fffff801fbd2eb40
rdx=00000000b02e6a50 rsi=00000000b02e6a50 rdi=fffff801fbd2ba90
rip=fffff801fbd24c7b rsp=ffff970dc858e7d0 rbp=fffff801fbd29630
r8=0000000000000009 r9=0000000000000000 r10=ffffd98db17d0fa0
r11=ffff970dc858e8a0 r12=ffffd98db0e46180 r13=ffffd98db0e46030
r14=0000000000000009 r15=fffff801fbd29600
iopl=0 nv up ei pl zr na po nc
cs=0010 ss=0018 ds=002b es=002b fs=0053 gs=002b efl=00010246
Ch64USB+0x14c7b:
fffff801
fbd24c7b 0fb616 movzx edx,byte ptr [rsi] ds:002b:00000000b02e6a50=??Resetting default scope
CPU_COUNT: 4
CPU_MHZ: 5da
CPU_VENDOR: GenuineIntel
CPU_FAMILY: 6
CPU_MODEL: 5c
CPU_STEPPING: 9
CPU_MICROCODE: 6,5c,9,0 (F,M,S,R) SIG: 32'00000000 (cache) 32'00000000 (init)
DEFAULT_BUCKET_ID: WIN8_DRIVER_FAULT
PROCESS_NAME: System
CURRENT_IRQL: 0
FOLLOWUP_IP:
Ch64USB+14c7b
fffff801`fbd24c7b 0fb616 movzx edx,byte ptr [rsi]
BUGCHECK_STR: AV
READ_ADDRESS: 00000000b02e6a50
ERROR_CODE: (NTSTATUS) 0xc0000005 - The instruction at 0x%p referenced memory at 0x%p. The memory could not be %s.
EXCEPTION_CODE_STR: c0000005
EXCEPTION_PARAMETER1: 0000000000000000
EXCEPTION_PARAMETER2: 00000000b02e6a50
ANALYSIS_SESSION_HOST: WIN10WORK
ANALYSIS_SESSION_TIME: 11-06-2018 09:38:07.0276
ANALYSIS_VERSION: 10.0.17763.1 amd64fre
LAST_CONTROL_TRANSFER: from fffff801fbd1558a to fffff801fbd24c7b
STACK_TEXT:
ffff970d
c858e7d0 fffff801fbd1558a : ffffd98db0e46030 fffff801fbd2eb40 ffffd98db0e46180 0000000000000000 : Ch64USB+0x14c7bffff970d
c858e830 fffff801fbd14012 : ffffd98db4b3b450 fffff800f676a560 ffffd98db52e8498 ffffd98db0e46180 : Ch64USB+0x558affff970d
c858e940 fffff801fbd11fc4 : ffffd98db0e46030 ffffd98db61f31e0 ffffd98db4b3b450 0000000000000000 : Ch64USB+0x4012ffff970d
c858e990 fffff800f66c2199 : 0000000000000000 ffff970dc858eb18 0000000000000000 ffff970dc858ea70 : Ch64USB+0x1fc4ffff970d
c858e9d0 fffff801fc215c2f : 0000000000000000 0000000000000000 ffffea9826d1f5cc 0000000000000000 : nt!IofCallDriver+0x59ffff970d
c858ea10 fffff801fc2161f1 : ffffd98db530c280 0000000000000000 fffff801f860a6c0 fffff801f836e4cc : hidusb!HumGetPortStatus+0x8fffff970d
c858eaa0 fffff800f67c5a9c : ffffd98db61f31e0 0000000000000000 0000000000000000 0000000000000100 : hidusb!HumResetWorkItem+0x61ffff970d
c858eb10 fffff800f671f285 : 0000000000000100 ffffd98db0736040 fffff800f67c5970 7f2222220000000c : nt!IopProcessWorkItem+0x12cffff970d
c858eb80 fffff800f67a2e37 : ffffd98db0736040 0000000000000080 ffffd98db0303440 ffffd98db0736040 : nt!ExpWorkerThread+0xf5ffff970d
c858ec10 fffff800f6859116 : ffffc28123179180 ffffd98db0736040 fffff800f67a2df0 6cc1166ccb2be5c0 : nt!PspSystemThreadStartup+0x47ffff970d
c858ec60 0000000000000000 : ffff970dc858f000 ffff970dc8589000 0000000000000000 0000000000000000 : nt!KiStartSystemThread+0x16THREAD_SHA1_HASH_MOD_FUNC: f5b4ace2adf39990f92c24669368e0ec71708e59
THREAD_SHA1_HASH_MOD_FUNC_OFFSET: e3eb8ce004d8d64f72274c1e0ef735d7b84651cf
THREAD_SHA1_HASH_MOD: dcb03cc04fbc0323c9cf8317ab1160cd6291736a
FAULT_INSTR_CODE: 4c16b60f
SYMBOL_STACK_INDEX: 0
SYMBOL_NAME: Ch64USB+14c7b
FOLLOWUP_NAME: MachineOwner
MODULE_NAME: Ch64USB
IMAGE_NAME: Ch64USB.sys
DEBUG_FLR_IMAGE_TIMESTAMP: 50868011
STACK_COMMAND: .cxr 0xffff970dc858dde0 ; kb
BUCKET_ID_FUNC_OFFSET: 14c7b
FAILURE_BUCKET_ID: AV_Ch64USB!unknown_function
BUCKET_ID: AV_Ch64USB!unknown_function
PRIMARY_PROBLEM_CLASS: AV_Ch64USB!unknown_function
TARGET_TIME: 2018-11-06T08:37:27.000Z
OSBUILD: 17134
OSSERVICEPACK: 0
SERVICEPACK_NUMBER: 0
OS_REVISION: 0
SUITE_MASK: 272
PRODUCT_TYPE: 1
OSPLATFORM_TYPE: x64
OSNAME: Windows 10
OSEDITION: Windows 10 WinNt TerminalServer SingleUserTS
OS_LOCALE:
USER_LCID: 0
OSBUILD_TIMESTAMP: 2018-08-03 05:10:45
BUILDDATESTAMP_STR: 180410-1804
BUILDLAB_STR: rs4_release
BUILDOSVER_STR: 10.0.17134.1.amd64fre.rs4_release.180410-1804
ANALYSIS_SESSION_ELAPSED_TIME: 12f6
ANALYSIS_SOURCE: KM
FAILURE_ID_HASH_STRING: km:av_ch64usb!unknown_function
FAILURE_ID_HASH: {f0a075df-a4e3-29fb-7038-fd226ffd6fc4}
Followup: MachineOwner
Good for you. Wait... are you taking offense and scolding me, because I spent time answering your question and trying to be sure you understood the underlying concepts?
Peter
Peter Viscarola
OSR
@OSRDrivers
On Tue, Nov 6, 2018 at 11:01 AM Peter_Viscarola_(OSR)
wrote:
> OSR https://community.osr.com/
> Peter_Viscarola_(OSR) commented on Upper filter driver waitlock
>
> > I am a developer on the user land since many years and I know for what
> we need locks
>
> Good for you. Wait... are you taking offense and scolding me, because I
> spent time answering your question and trying to be sure you understood the
> underlying concepts?
>
>
>
> Peter
>
> --
> Reply to this email directly or follow the link below to check it out:
> https://community.osr.com/discussion/comment/291310#Comment_291310
>
> Check it out:
> https://community.osr.com/discussion/comment/291310#Comment_291310
>
Peter, sorry if I answered in a way that bother you. I thank you very much and the others to answer my sometimes not so deeply grounded questions.
Jamey_Kirby: Can we see some source around the bugcheck?
That is the problem. I can not say at the moment where in the code the bugcheck occurres exactly. If I can reproduce the bug, I will come back.
ffff970dc858e7d0 fffff801fbd1558a : ffffd98db0e46030 fffff801fbd2eb40
ffffd98db0e46180 0000000000000000 : Ch64USB+0x14c7b
ffff970dc858e830 fffff801fbd14012 : ffffd98db4b3b450 fffff800f676a560
ffffd98db52e8498 ffffd98db0e46180 : Ch64USB+0x558a
ffff970dc858e940 fffff801fbd11fc4 : ffffd98db0e46030 ffffd98db61f31e0
ffffd98db4b3b450 0000000000000000 : Ch64USB+0x4012
ffff970dc858e990 fffff800f66c2199 : 0000000000000000 ffff970dc858eb18
0000000000000000 ffff970dc858ea70 : Ch64USB+0x1fc4
ffff970dc858e9d0 fffff801fc215c2f : 0000000000000000 0000000000000000
ffffea9826d1f5cc 0000000000000000 : nt!IofCallDriver+0x59
Start with your IoCallDriver() and work your way down.
On Tue, Nov 6, 2018 at 11:46 AM Mak
wrote:
> OSR https://community.osr.com/
> Mak commented on Upper filter driver waitlock
>
> Jamey_Kirby: Can we see some source around the bugcheck?
>
> That is the problem. I can not say at the moment where in the code the
> bugcheck occurres exactly. If I can reproduce the bug, I will come back.
>
> --
> Reply to this email directly or follow the link below to check it out:
> https://community.osr.com/discussion/comment/291316#Comment_291316
>
> Check it out:
> https://community.osr.com/discussion/comment/291316#Comment_291316
>
If I search my code, I cant find a function with the name IofCallDriver or more reduced "CallDriver".
Fix your symbols. Read or watch this. Unless you already know how to do that, too.
Peter
Peter Viscarola
OSR
@OSRDrivers
I set the symbols path to:
_NT_SYMBOL_PATH=symsrv*symsrv.dll*D:\Symbols*http://msdl.microsoft.com/download/symbols
but If I look on the driver the symbols are always loaded to "C:\ProgramData\dbg\sym".
I checked the environment variable in VS and under System.
The symbols loading summary is:
************* Symbol Loading Error Summary **************
Module name Error
clipsp No error - symbol load deferred
WdFilter The system cannot find the file specified
igdkmd64 The system cannot find the file specified
drmk The system cannot find the file specified
TeeDriverW8x64 The system cannot find the file specified
RtsP2Stor The system cannot find the file specified
Netwtw04 The system cannot find the file specified
iaLPSS2_UART2 The system cannot find the file specified
iaLPSS2_SPI The system cannot find the file specified
IntcDAud The system cannot find the file specified
kbfiltr No error - symbol load deferred
ibtusb The system cannot find the file specified
Ch64USB The system cannot find the file specified
peauth The system cannot find the file specified
WdNisDrv The system cannot find the file specified
Is this ok?
> Since I use the locks I get the following bugcheck and have no idea where I must look in the code:
>
>
> * *
> * Bugcheck Analysis *
> * *
>
> SYSTEM_THREAD_EXCEPTION_NOT_HANDLED (7e)
> ...
> Arguments:
> Arg1: ffffffffc0000005, The exception code that was not handled
> Arg2: fffff801fbd24c7b, The address that the exception occurred at
> Arg3: ffff970dc858e598, Exception Record Address
> Arg4: ffff970dc858dde0, Context Record Address
> ...
> Attempt to read from address 00000000b02e6a50
>
> CONTEXT: ffff970dc858dde0 -- (.cxr 0xffff970dc858dde0)
> rax=ffffd98db0e46030 rbx=0000000000000001 rcx=fffff801fbd2eb40
> rdx=00000000b02e6a50 rsi=00000000b02e6a50 rdi=fffff801fbd2ba90
> rip=fffff801fbd24c7b rsp=ffff970dc858e7d0 rbp=fffff801fbd29630
> r8=0000000000000009 r9=0000000000000000 r10=ffffd98db17d0fa0
> r11=ffff970dc858e8a0 r12=ffffd98db0e46180 r13=ffffd98db0e46030
> r14=0000000000000009 r15=fffff801fbd29600
> iopl=0 nv up ei pl zr na po nc
> cs=0010 ss=0018 ds=002b es=002b fs=0053 gs=002b efl=00010246
> Ch64USB+0x14c7b:
> fffff801fbd24c7b 0fb616 movzx edx,byte ptr [rsi] ds:002b:00000000b02e6a50=??
That seems crystal clear. You're trying to read a user-mode address
within your driver.
> I set the symbols path to:
> _NT_SYMBOL_PATH=symsrv*symsrv.dll*D:\Symbols*http://msdl.microsoft.com/download/symbols
> but If I look on the driver the symbols are always loaded to "C:\ProgramData\dbg\sym".
Did you copy your own driver's symbols there? I'm guessing you didn't.
In that case, you probably want to add the directory containing your
driver's symbols to the .sympath.
Tim Roberts, [email protected]
Providenza & Boekelheide, Inc.
If you examine the kernel stack and it has symbols resolved, then yes. If not, then no.
Let me guess: You didn't read that page I sent you to, or watch that video... did you. No, I bet you didn't.
Seems I'm pretty much wasting my time here. Good luck, OP...
Peter
Peter Viscarola
OSR
@OSRDrivers
looked for it as I always want to read what you recommend
On Tue, Nov 6, 2018 at 4:23 PM Peter_Viscarola_(OSR)
wrote:
> OSR https://community.osr.com/
> Peter_Viscarola_(OSR) commented on Upper filter driver waitlock
>
> > Is this ok?
>
> If you examine the kernel stack and it has symbols resolved, then yes. If
> not, then no.
>
> Let me guess: You didn't read that page I sent you to, or watch that
> video... did you. No, I bet you didn't.
>
> Seems I'm pretty much wasting my time here. Good luck, OP...
>
> Peter
>
> --
> Reply to this email directly or follow the link below to check it out:
> https://community.osr.com/discussion/comment/291325#Comment_291325
>
> Check it out:
> https://community.osr.com/discussion/comment/291325#Comment_291325
>
Yet YOU managed to figure it out. And I’ll wager that you need a tutorial about how to setup the WinDbg symbol search path even less than I do.
Yeah.
P
Peter Viscarola
OSR
@OSRDrivers
rarely need the kernel symbols. Usually, my own symbols suffice. I guess it
is a matter of knowing your environment and your code.
On Tue, Nov 6, 2018 at 8:33 PM Peter_Viscarola_(OSR)
wrote:
> OSR https://community.osr.com/
> Peter_Viscarola_(OSR) commented on Upper filter driver waitlock
>
> > In Mak's defense, the link did not come through in the email
>
> Yet YOU managed to figure it out. And I’ll wager that you need a tutorial
> about how to setup the WinDbg symbol search path even less than I do.
>
> Yeah.
>
> P
>
> --
> Reply to this email directly or follow the link below to check it out:
> https://community.osr.com/discussion/comment/291328#Comment_291328
>
> Check it out:
> https://community.osr.com/discussion/comment/291328#Comment_291328
>
Peter, I read and watched that article. The search path is set correctly but as I mentioned above the pdb are loaded on the c drive. If I delete the symbols on the c drive they are loaded again. It seems my settings are ignored "d:\Symbols".
\symbolshttps://msdl.microsoft.com/download/symbols;D:\project\sys\x64\Debug
If I open the symbol path in windbg I also see the path to my driver pdb. By the way if the program crashes on other places I see in the stack trace my functions and part of my function code. The things are not totally wrong.
This is from the symbol path dialog:
srv
Tim:
within your driver.
What is wrong about that? I communicate with the driver and copy some data to driver string lists.
>>> That seems crystal clear. You're trying to read a user-mode address within your driver.
> What is wrong about that? I communicate with the driver and copy some data to driver string lists.
How, exactly, are you doing that? Are you passing addresses in your ioctl data? That is a HUGE mistake. It is tricky to handle user-mode addresses in a driver. You have to be absolutely sure that your process is still in the page tables (which we call "the process context"). If you are using KMDF, then your EvtIoDeviceControl is NOT called in the original process context, so any of that processes addresses will be invalid. Even if you are in the proper process context, the user-mode pages can get freed at any point, causing a blue screen. You have to use "probe and lock" to lock the pages into memory and convert to a kernel mode address.
Pass your data in the ioctl buffers. Don't ever pass addresses.
Tim Roberts, [email protected]
Providenza & Boekelheide, Inc.
Tim worte:
I have no lock while I am doing this but locks at the moment the data are placed into the lists.
>>> How, exactly, are you doing that?
> * CreateFile with overlapped structure
> * IOCTL... for getting the buffer length
> * IOCTL... to get and set data, the buffer is crc and length checked
> * all data are copied into NopagedPool unicode string array memory
What ioctl codes? Is it possible you are using METHOD_NEITHER? What do
your "get" and "set" buffers look like?
Tim Roberts, [email protected]
Providenza & Boekelheide, Inc.
Tim worte:
define IOCTL_NONPNP_METHOD_GET_GETPROPERTY \
...
this is the pattern which all get follows:
// IOCTL_NONPNP_METHOD_GET_BUFFER_SIZE
>
> Tim worte:
>
>>> What ioctl codes?
>
> define IOCTL_NONPNP_METHOD_GET_GETPROPERTY \
> CTL_CODE( FILEIO_TYPE, 0x902, METHOD_BUFFERED , FILE_ANY_ACCESS )
> ...
>
> this is the pattern which all get follows:
>
> // IOCTL_NONPNP_METHOD_GET_BUFFER_SIZE
Honestly. Do people really not know how to ask questions to get help? You showed me the define for one ioctl, and the code for the other. Did that really seem like a good idea? Which one is causing your crash? I assume it's not the "get buffer size" ioctl, since the code you showed doesn't even use the input buffer. In that, case why on earth would that be the one you chose to show us? SHOW US THE CODE THAT IS BROKEN. Why do I even have to say that?
And if this is really an upper filter driver, then it is obviously a PNP driver. WHY on earth would you keep naming your ioctls IOCTL_NONPNP_xxx? It drives me absolutely bonkers that people blindly copy code from the samples and keep the same, obviously non-applicable names for constants, functions, and files. Take a little care with your software engineering. Do it right, or don't do it at all.
Man, I must be in a bad mood.
> status = WdfRequestRetrieveInputBuffer(Request, 0, (PVOID*)&inBuf, &bufSize); if (!NT_SUCCESS(status) || bufSize < sizeof(ULONG)) { status = STATUS_INSUFFICIENT_RESOURCES; break; } status = WdfRequestRetrieveOutputBuffer(Request, 0, (PVOID*)&buffer, &bufSize); if (!NT_SUCCESS(status)) { break; } if (bufSize == sizeof(ULONG)) { *((USHORT*)buffer) = (USHORT)TRANSFERBUFFER_SIZE; } WdfRequestSetInformation(Request, OutputBufferLength);
Why do you require the user to provide an input buffer of 4 bytes and fetch its address, when you don't use the input buffer at all? If this is an output-only ioctl, then write it as an output-only ioctl. Skip the input buffer altogether. And why do you require the output buffer to be a ULONG when you are only returning a USHORT? And why do you go to the trouble of casting the constant to a USHORT at all? Why not just write *buffer = TRANSFERBUFFER_SIZE? And if it is a constant, as an all-caps value should always be, then why even have an ioctl? Why not just put it in a common #include file?
—
Tim Roberts, [email protected]
Providenza & Boekelheide, Inc.
Tim Roberts, [email protected]
Providenza & Boekelheide, Inc.