cpu: assert host pointer offset within block

Make accesses safer in case we missed some
check somewhere.
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Reviewed-by: NPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: NAmos Kong <akong@redhat.com>
Signed-off-by: NAmit Shah <amit.shah@redhat.com>

include/exec/cpu-all.h

@@ -315,6 +315,7 @@ typedef struct RAMBlock {
 
 static inline void *ramblock_ptr(RAMBlock *block, ram_addr_t offset)
 {
+    assert(offset < block->length);
     return (char *)block->host + offset;
 }