2016-03-25  Florian Weimer  <fweimer@redhat.com>

	[BZ #19868]
	* resolv/nss_dns/dns-network.c (getanswer_r): Implement additional
	DNS packet syntax checks (which were not needed before).  Skip
	over non-PTR records.

Index: glibc-2.23/resolv/nss_dns/dns-network.c
===================================================================
--- glibc-2.23.orig/resolv/nss_dns/dns-network.c
+++ glibc-2.23/resolv/nss_dns/dns-network.c
@@ -345,10 +345,23 @@ getanswer_r (const querybuf *answer, int
       if (n < 0 || res_dnok (bp) == 0)
 	break;
       cp += n;
+
+      if (end_of_message - cp < 10)
+	{
+	  __set_h_errno (NO_RECOVERY);
+	  return NSS_STATUS_UNAVAIL;
+	}
+
       GETSHORT (type, cp);
       GETSHORT (class, cp);
       cp += INT32SZ;		/* TTL */
-      GETSHORT (n, cp);
+      uint16_t rdatalen;
+      GETSHORT (rdatalen, cp);
+      if (end_of_message - cp < rdatalen)
+	{
+	  __set_h_errno (NO_RECOVERY);
+	  return NSS_STATUS_UNAVAIL;
+	}
 
       if (class == C_IN && type == T_PTR)
 	{
@@ -370,7 +383,7 @@ getanswer_r (const querybuf *answer, int
 	      cp += n;
 	      return NSS_STATUS_UNAVAIL;
 	    }
-	  cp += n;
+	  cp += rdatalen;
          if (alias_pointer + 2 < &net_data->aliases[MAX_NR_ALIASES])
            {
              *alias_pointer++ = bp;
@@ -381,6 +394,9 @@ getanswer_r (const querybuf *answer, int
              ++have_answer;
            }
 	}
+      else
+	/* Skip over unknown record data.  */
+	cp += rdatalen;
     }
 
   if (have_answer)