11927 Log, or optionally panic, on zero-length kmem allocations
Reviewed by: Dan McDonald <danmcd@joyent.com>
Reviewed by: Jason King <jason.brian.king@gmail.com>

@@ -850,11 +850,12 @@
          * We don't need to hold fi_lock because all other lwp's in the
          * parent have been held.
          */
         cfip->fi_nfiles = nfiles = flist_minsize(pfip);
 
-        cfip->fi_list = kmem_zalloc(nfiles * sizeof (uf_entry_t), KM_SLEEP);
+        cfip->fi_list = nfiles == 0 ? NULL :
+            kmem_zalloc(nfiles * sizeof (uf_entry_t), KM_SLEEP);
 
         for (fd = 0, pufp = pfip->fi_list, cufp = cfip->fi_list; fd < nfiles;
             fd++, pufp++, cufp++) {
                 cufp->uf_file = pufp->uf_file;
                 cufp->uf_alloc = pufp->uf_alloc;