s390/numa: always use logical cpu and core ids

The toptree algorithm uses the physical core ids to create a mapping
between cores and nodes (to_node_id array within emu_cores structure).
The core ids are used as an index into an array which size depends on
CONFIG_NR_CPUS. If the physical core ids are larger, this will result
in out-of-bounds write accesses.

Generate logical core ids instead to avoid this.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/smp.h

@@ -69,6 +69,12 @@ static inline void smp_stop_cpu(void)
 	}
 }
 
+/* Return thread 0 CPU number as base CPU */
+static inline int smp_get_base_cpu(int cpu)
+{
+	return cpu - (cpu % (smp_cpu_mtid + 1));
+}
+
 #ifdef CONFIG_HOTPLUG_CPU
 extern int smp_rescan_cpus(void);
 extern void __noreturn cpu_die(void);

arch/s390/numa/mode_emu.c

@@ -360,7 +360,7 @@ static struct toptree *toptree_from_topology(void)
 		drawer = toptree_get_child(node, top->drawer_id);
 		book = toptree_get_child(drawer, top->book_id);
 		mc = toptree_get_child(book, top->socket_id);
-		core = toptree_get_child(mc, top->core_id);
+		core = toptree_get_child(mc, smp_get_base_cpu(cpu));
 		if (!drawer || !book || !mc || !core)
 			panic("NUMA emulation could not allocate memory");
 		cpumask_set_cpu(cpu, &core->mask);