PSECURITY_DESCRIPTOR
NTAPI
ObpReferenceSecurityDescriptor(IN POBJECT_HEADER ObjectHeader)
{
PSECURITY_DESCRIPTOR SecurityDescriptor;
PSECURITY_DESCRIPTOR_HEADER SdHeader;
PEX_FAST_REF FastRef;
EX_FAST_REF OldValue;
ULONG_PTR Count;
/* Acquire a reference to the security descriptor */
FastRef = (PEX_FAST_REF)&ObjectHeader->SecurityDescriptor;
OldValue = ExAcquireFastReference(FastRef);
/* Get the descriptor and reference count */
SecurityDescriptor = ExGetObjectFastReference(OldValue);
Count = ExGetCountFastReference(OldValue);
/* Check if there's no descriptor or if there's still cached references */
if ((Count >= 1) || !(SecurityDescriptor))
{
/* Check if this is the last reference */
if (Count == 1)
{
/* Add the extra references that we'll take */
SdHeader = ObpGetHeaderForSd(SecurityDescriptor);
InterlockedExchangeAdd((PLONG)&SdHeader->RefCount, MAX_FAST_REFS);
/* Now insert them */
if (!ExInsertFastReference(FastRef, SecurityDescriptor))
{
/* Undo the references since we failed */
InterlockedExchangeAdd((PLONG)&SdHeader->RefCount,
-MAX_FAST_REFS);
}
}
/* Return the SD */
return SecurityDescriptor;
}
/* Lock the object */
ObpAcquireObjectLockShared(ObjectHeader);
/* Get the object header */
SecurityDescriptor = ExGetObjectFastReference(*FastRef);
SdHeader = ObpGetHeaderForSd(SecurityDescriptor);
/* Do the reference */
InterlockedIncrement((PLONG)&SdHeader->RefCount);
/* Release the lock and return */
ObpReleaseObjectLock(ObjectHeader);
return SecurityDescriptor;
}
PEX_CALLBACK_ROUTINE_BLOCK
NTAPI
ExReferenceCallBackBlock(IN OUT PEX_CALLBACK CallBack)
{
EX_FAST_REF OldValue;
ULONG_PTR Count;
PEX_CALLBACK_ROUTINE_BLOCK CallbackBlock;
/* Acquire a reference */
OldValue = ExAcquireFastReference(&CallBack->RoutineBlock);
Count = ExGetCountFastReference(OldValue);
/* Fail if there isn't any object */
if (!ExGetObjectFastReference(OldValue)) return NULL;
/* Check if we don't have a reference */
if (!Count)
{
/* FIXME: Race */
DPRINT1("Unhandled callback race condition\n");
ASSERT(FALSE);
return NULL;
}
/* Get the callback block */
CallbackBlock = ExGetObjectFastReference(OldValue);
/* Check if this is the last reference */
if (Count == 1)
{
/* Acquire rundown protection */
if (ExfAcquireRundownProtectionEx(&CallbackBlock->RundownProtect,
MAX_FAST_REFS))
{
/* Insert references */
if (!ExInsertFastReference(&CallBack->RoutineBlock, CallbackBlock))
{
/* Backdown the rundown acquire */
ExfReleaseRundownProtectionEx(&CallbackBlock->RundownProtect,
MAX_FAST_REFS);
}
}
}
/* Return the callback block */
return CallbackBlock;
}
