fixed vulnerability (kernel memory rewrite) in sysfn 30.2 and 30.5

git-svn-id: svn://kolibrios.org@8676 a494cfbc-eb01-0410-851d-a64ba20cac60

kernel/trunk/fs/fs_lfn.inc

@@ -458,6 +458,14 @@ sys_current_directory:  ; sysfunction 30
 
 .get:
 ; in: ecx -> buffer, edx = length, eax = encoding
+        stdcall is_region_userspace, ecx, edx
+        jnz     @f
+
+        ; if illegal buffer given
+        xor     edx, edx
+        jmp     .ret
+@@:
+
         mov     esi, edi
         inc     esi
         mov     edi, ecx