[2.28 COMMITTED] libanl: properly cleanup if first helper thread creation failed (bug 22927)

[Florian Weimer]

From: Andreas Schwab <schwab@suse.de>

(cherry picked from commit bd3b0fbae33a9a4cc5e2daf049443d5cf03d4251)

2018-11-05  Andreas Schwab  <schwab@suse.de>

	[BZ #22927]
	* resolv/gai_misc.c (__gai_enqueue_request): Don't crash if
	creating the first helper thread failed.

diff --git a/NEWS b/NEWS
index f3004915f2..b85be4a9c1 100644
--- a/NEWS
+++ b/NEWS
@@ -10,6 +10,7 @@ Version 2.28.1
 The following bugs are resolved with this release:
 
   [20209] localedata: Spelling mistake for Sunday in Greenlandic kl_GL
+  [22927] libanl: properly cleanup if first helper thread creation failed
   [23400] stdlib/test-bz22786.c creates temporary files in glibc source tree
   [23497] readdir64@GLIBC_2.1 cannot parse the kernel directory stream
   [23521] nss_files aliases database file stream leak
diff --git a/resolv/gai_misc.c b/resolv/gai_misc.c
index e7c3b63cc5..80a2cff835 100644
--- a/resolv/gai_misc.c
+++ b/resolv/gai_misc.c
@@ -261,8 +261,11 @@ __gai_enqueue_request (struct gaicb *gaicbp)
 	      /* We cannot create a thread in the moment and there is
 		 also no thread running.  This is a problem.  `errno' is
 		 set to EAGAIN if this is only a temporary problem.  */
-	      assert (lastp->next == newp);
-	      lastp->next = NULL;
+	      assert (requests == newp || lastp->next == newp);
+	      if (lastp != NULL)
+		lastp->next = NULL;
+	      else
+		requests = NULL;
 	      requests_tail = lastp;
 
 	      newp->next = freelist;