[ros-dev] Re: [ros-diffs] [navaraf] 17604: Check for Request == NULL.

[Filip Navara]

Hartmut Birr wrote:

>navaraf at svn.reactos.com wrote:
>
>  
>
>>Check for Request == NULL.
>>
>>Modified: trunk/reactos/ntoskrnl/lpc/reply.c
>> 
>>
>>------------------------------------------------------------------------
>>*Modified: trunk/reactos/ntoskrnl/lpc/reply.c*
>>
>>--- trunk/reactos/ntoskrnl/lpc/reply.c	2005-09-02 11:29:40 UTC (rev 17603)
>>+++ trunk/reactos/ntoskrnl/lpc/reply.c	2005-09-02 13:12:44 UTC (rev 17604)
>>@@ -263,6 +263,12 @@
>>
>>   Request = EiDequeueMessagePort(Port);
>>   KeReleaseSpinLock(&Port->Lock, oldIrql);
>>
>> 
>>
>>+   if (Request == NULL)
>>+     {
>>+       ObDereferenceObject(Port);
>>+       return STATUS_UNSUCCESSFUL;
>>+     }
>>+
>> 
>>
>>   if (Request->Message.u2.s2.Type == LPC_CONNECTION_REQUEST)
>>     {
>>       PORT_MESSAGE Header;
>> 
>>
>>    
>>
>Hi,
>
>I think that this fix doesn't solve the real problem. The caller waits
>on a semaphore and the semaphore is only signaled if a message is in the
>queue. This means, the caller can't get a NULL pointer from
>EiDequeueMessagePort(). The real problem is anywhere in
>KeWaitForSingleObject, which does return STATUS_USER_APC for a non
>alertable wait. That is wrong.
>  
>
There's only one case where KeWaitForSingleObject can return 
STATUS_USER_APC for non-alertable waits and that's when the thread is 
about to be terminated. It is correct behaviour of the routine. I 
believe we're hitting just this case here.

- Filip