HADOOP-10989. Work around buggy getgrouplist() implementations on Linux that return 0 on failure. Contributed by Chris Nauroth.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1619659 13f79535-47bb-0310-9956-ffa450edef68

hadoop-common-project/hadoop-common/CHANGES.txt

@@ -686,6 +686,9 @@ Release 2.6.0 - UNRELEASED
 
     HADOOP-10488. TestKeyProviderFactory fails randomly. (tucu)
 
+    HADOOP-10989. Work around buggy getgrouplist() implementations on Linux that
+    return 0 on failure. (cnauroth)
+
 Release 2.5.0 - 2014-08-11
 
   INCOMPATIBLE CHANGES

hadoop-common-project/hadoop-common/src/main/native/src/org/apache/hadoop/security/hadoop_user_info.c

@@ -193,7 +193,17 @@ int hadoop_user_info_getgroups(struct hadoop_user_info *uinfo)
   ngroups = uinfo->gids_size;
   ret = getgrouplist(uinfo->pwd.pw_name, uinfo->pwd.pw_gid, 
                          uinfo->gids, &ngroups);
+  // Return value is different on Linux vs. FreeBSD.  Linux: the number of groups
+  // or -1 on error.  FreeBSD: 0 on success or -1 on error.  Unfortunately, we
+  // can't accept a 0 return on Linux, because buggy implementations have been
+  // observed to return 0 but leave the other out parameters in an indeterminate
+  // state.  This deviates from the man page, but it has been observed in
+  // practice.  See issue HADOOP-10989 for details.
+#ifdef __linux__
+  if (ret > 0) {
+#else
   if (ret >= 0) {
+#endif
     uinfo->num_gids = ngroups;
     ret = put_primary_gid_first(uinfo);
     if (ret) {