Plug sharefs zone-shutdown leaks

@@ -23,10 +23,11 @@
  * Copyright (c) 2007, 2010, Oracle and/or its affiliates. All rights reserved.
  */
 
 /*
  * Copyright 2018 Nexenta Systems, Inc.
+ * Copyright 2019 Joyent, Inc.
  */
 
 #include <sys/types.h>
 #include <sys/types32.h>
 #include <sys/param.h>

@@ -307,10 +308,31 @@
         sharetab_globals_t *sg = data;
 
         rw_destroy(&sg->sharefs_lock);
         rw_destroy(&sg->sharetab_lock);
 
+        /* ALL of the allocated things must be cleaned before we free sg. */
+        while (sg->sharefs_sharetab != NULL) {
+                int i;
+                sharetab_t *freeing = sg->sharefs_sharetab;
+
+                sg->sharefs_sharetab = freeing->s_next;
+                kmem_free(freeing->s_fstype, strlen(freeing->s_fstype) + 1);
+                for (i = 0; i < PKP_HASH_SIZE; i++) {
+                        sharefs_hash_head_t *bucket;
+
+                        bucket = &(freeing->s_buckets[i]);
+                        while (bucket->ssh_sh != NULL) {
+                                share_t *share = bucket->ssh_sh;
+
+                                bucket->ssh_sh = share->sh_next;
+                                sharefree(share, NULL);
+                        }
+                }
+                kmem_free(freeing, sizeof (*freeing));
+        }
+
         kmem_free(sg, sizeof (*sg));
 }
 
 void
 sharefs_sharetab_init(void)