[Wine-patches] [eterhack] ntoskrnl.exe: Make KeWaitForSingleObject yield execution to another thread if there is nothing to wait on. (eterbug #4884)

[Dmitry Timoshkov]

hardlock.sys does:

PRKEVENT global_event;
PRKTHREAD system_thread;

load_driver_entry()
{
    global_event = KeInitializeEvent(SynchronizationEvent);
    PsCreateSystemThread(system_thread_entry);
}

system_thread_entry()
{
    system_thread = KeGetCurrentThread();
    KeWaitForSingleObject(global_event);
}

unload_driver_entry()
{
    KeSetEvent(global_event);
    KeWaitForSingleObject(system_thread);
}

Since KeGetCurrentThread() is a stub and it returns NULL, then
KeWaitForSingleObject(system_thread) doesn't wait, and when system thread
gets control the driver PE module is already unloaded from memory => BOOM.

Instead of implementing full PRKTHREAD object synchronization support this
patch simply yields the control in the hope that the target thread wakes up
and does its job.
---
 dlls/ntoskrnl.exe/ntoskrnl.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/dlls/ntoskrnl.exe/ntoskrnl.c b/dlls/ntoskrnl.exe/ntoskrnl.c
index 9daf064..09068ee 100644
--- a/dlls/ntoskrnl.exe/ntoskrnl.c
+++ b/dlls/ntoskrnl.exe/ntoskrnl.c
@@ -2798,7 +2798,11 @@ NTSTATUS WINAPI KeWaitForSingleObject(PVOID Object,
 
     TRACE( "%p, %d, %d, %d, %p\n", Object, WaitReason, WaitMode, Alertable, Timeout );
 
-    if (!Object) return STATUS_INVALID_PARAMETER;
+    if (!Object)
+    {
+        ZwYieldExecution();
+        return STATUS_SUCCESS;
+    }
 
     switch (header->Type)
     {
-- 
1.7.12.1