Avoid infinite loop in nss_dns getnetbyname [BZ #17630]

ChangeLog

@@ -1,3 +1,9 @@
+2014-12-16  Florian Weimer  <fweimer@redhat.com>
+
+	[BZ #17630]
+	* resolv/nss_dns/dns-network.c (getanswer_r): Iterate over alias
+	names.
+
 2014-12-16  Allan McRae  <allan@archlinux.org>
 
 	* stdio-common/Makefile (tests): Re-add bug26.

NEWS

@@ -13,8 +13,8 @@ Version 2.21
   15884, 16469, 16617, 16619, 16657, 16740, 16857, 17192, 17266, 17344,
   17363, 17370, 17371, 17411, 17460, 17475, 17485, 17501, 17506, 17508,
   17522, 17555, 17570, 17571, 17572, 17573, 17574, 17581, 17582, 17583,
-  17584, 17585, 17589, 17594, 17601, 17608, 17616, 17625, 17633, 17634,
-  17647, 17653, 17657, 17664, 17665, 17668, 17682.
+  17584, 17585, 17589, 17594, 17601, 17608, 17616, 17625, 17630, 17633,
+  17634, 17647, 17653, 17657, 17664, 17665, 17668, 17682.
 
 * CVE-2104-7817 The wordexp function could ignore the WRDE_NOCMD flag
   under certain input conditions resulting in the execution of a shell for
@@ -25,6 +25,9 @@ Version 2.21
 * CVE-2012-3406 printf-style functions could run into a stack overflow when
   processing format strings with a large number of format specifiers.
 
+* The nss_dns implementation of getnetbyname could run into an infinite loop
+  if the DNS response contained a PTR record of an unexpected format.
+
 * The minimum GCC version that can be used to build this version of the GNU
   C Library is GCC 4.6.  Older GCC versions, and non-GNU compilers, can
   still be used to compile programs using the GNU C Library.

resolv/nss_dns/dns-network.c

@@ -398,8 +398,8 @@ getanswer_r (const querybuf *answer, int anslen, struct netent *result,
 
 	case BYNAME:
 	  {
-	    char **ap = result->n_aliases++;
-	    while (*ap != NULL)
+	    char **ap;
+	    for (ap = result->n_aliases; *ap != NULL; ++ap)
 	      {
 		/* Check each alias name for being of the forms:
 		   4.3.2.1.in-addr.arpa		= net 1.2.3.4