uvm_mapent_alloc() & NULL check

[Martin Pieuchot]

Variable `me' is never NULL before reaching RBT_POISON().  Diff has a
lot of context to ease the review.

CID 1453116 Dereference before null check

ok?

Index: uvm/uvm_map.c
===================================================================
RCS file: /cvs/src/sys/uvm/uvm_map.c,v
retrieving revision 1.263
diff -u -p -u -2 -0 -r1.263 uvm_map.c
--- uvm/uvm_map.c       4 Mar 2020 21:15:38 -0000       1.263
+++ uvm/uvm_map.c       24 Mar 2020 15:06:26 -0000
@@ -1736,44 +1736,41 @@ uvm_mapent_alloc(struct vm_map *map, int
                }
                me = SLIST_FIRST(&uvm.kentry_free);
                SLIST_REMOVE_HEAD(&uvm.kentry_free, daddrs.addr_kentry);
                uvmexp.kmapent++;
                mtx_leave(&uvm_kmapent_mtx);
                me->flags = UVM_MAP_STATIC;
        } else if (map == kernel_map) {
                splassert(IPL_NONE);
                me = pool_get(&uvm_map_entry_kmem_pool, pool_flags);
                if (me == NULL)
                        goto out;
                me->flags = UVM_MAP_KMEM;
        } else {
                splassert(IPL_NONE);
                me = pool_get(&uvm_map_entry_pool, pool_flags);
                if (me == NULL)
                        goto out;
                me->flags = 0;
        }
 
-       if (me != NULL) {
-               RBT_POISON(uvm_map_addr, me, UVMMAP_DEADBEEF);
-       }
-
+       RBT_POISON(uvm_map_addr, me, UVMMAP_DEADBEEF);
 out:
        return(me);
 }
 
 /*
  * uvm_mapent_free: free map entry
  *
  * => XXX: static pool for kernel map?
  */
 void
 uvm_mapent_free(struct vm_map_entry *me)
 {
        if (me->flags & UVM_MAP_STATIC) {
                mtx_enter(&uvm_kmapent_mtx);
                SLIST_INSERT_HEAD(&uvm.kentry_free, me, daddrs.addr_kentry);
                uvmexp.kmapent--;
                mtx_leave(&uvm_kmapent_mtx);
        } else if (me->flags & UVM_MAP_KMEM) {
                splassert(IPL_NONE);
                pool_put(&uvm_map_entry_kmem_pool, me);