memory leak with RCU_TABLE_FREE

commit e73b7fff upstream.

The rcu page table free code uses a couple of bits in the page table
pointer passed to tlb_remove_table to discern the different page table
types. __tlb_remove_table extracts the type with an incorrect mask which
leads to memory leaks. The correct mask is ((FRAG_MASK << 4) | FRAG_MASK).
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

arch/s390/mm/pgtable.c

@@ -291,8 +291,9 @@ void page_table_free_rcu(struct mmu_gather *tlb, unsigned long *table)
 
 void __tlb_remove_table(void *_table)
 {
-	void *table = (void *)((unsigned long) _table & PAGE_MASK);
-	unsigned type = (unsigned long) _table & ~PAGE_MASK;
+	const unsigned long mask = (FRAG_MASK << 4) | FRAG_MASK;
+	void *table = (void *)((unsigned long) _table & ~mask);
+	unsigned type = (unsigned long) _table & mask;
 
 	if (type)
 		__page_table_free_rcu(table, type);