server: Fix for possible desktop variable being NULL when set_process_default_desktop is called

[Robert Shearman]

Alexandre Julliard wrote:

>Robert Shearman <rob at codeweavers.com> writes:
>
>  
>
>>   /* check for an inherited winstation handle (don't ask...) */
>>   if ((handle = find_inherited_handle( process, &winstation_ops )))
>>   {
>>       winstation = (struct winstation *)get_handle_obj( process,
>>handle, 0, &winstation_ops );
>>   }
>>   else if (parent && parent->process->winstation)
>>   {
>>       handle = duplicate_handle( parent->process,
>>parent->process->winstation,
>>                                  process, 0, 0, DUP_HANDLE_SAME_ACCESS );
>>       winstation = (struct winstation *)get_handle_obj( process,
>>handle, 0, &winstation_ops );
>>   }
>>   if (!winstation) goto done;
>>   process->winstation = handle;
>>
>>Handle is guaranteed to be non-NULL here, since winstation and handle
>>are the same object (well, except if duplicate_handle fails).
>>    
>>
>
>Yes, it's non-NULL here, but that's irrelevant since it's reset on the
>next line.
>  
>

Sorry, you are correct. It does indeed look like a flaw in the scanner:

At conditional (5): "handle = find_inherited_handle != 0" taking false path

298          if ((handle = find_inherited_handle( process, &desktop_ops )))
...
Event var_deref_model: Variable "desktop" tracked as NULL was passed to 
a function that dereferences it. [model]
Also see events: [assign_zero]
At conditional (8): "handle != 0" taking true path
311          if (handle) set_process_default_desktop( process, desktop, 
handle );

It doesn't seem to have tracked that handle was assigned zero on line 298.

-- 
Rob Shearman