Fix memory leak in _nss_dns_gethostbyname4_r with big DNS answer

3 files changed, 17 insertions, 3 deletions

diff --git a/ChangeLog b/ChangeLog
index 2d6e872fb2..2d060dfa92 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2014-02-13  Andreas Schwab  <schwab@suse.de>
+
+	[BZ #16574]
+	* resolv/nss_dns/dns-host.c (_nss_dns_gethostbyname4_r): Free the
+	second answer buffer if it was separately allocated.
+
 2014-02-12  Joseph Myers  <joseph@codesourcery.com>
 
 	* sysdeps/mips/math-tests.h: Include <features.h>.
diff --git a/NEWS b/NEWS
index 8df0bfaaa7..6de1d455e7 100644
--- a/NEWS
+++ b/NEWS
@@ -9,7 +9,7 @@ Version 2.20
 
 * The following bugs are resolved with this release:
 
-  15894, 16447, 16545.
+  15894, 16447, 16545, 16574.
 
 * The am33 port, which had not worked for several years, has been removed
   from ports.
diff --git a/resolv/nss_dns/dns-host.c b/resolv/nss_dns/dns-host.c
index 541c25a348..365de7095f 100644
--- a/resolv/nss_dns/dns-host.c
+++ b/resolv/nss_dns/dns-host.c
@@ -298,13 +298,14 @@ _nss_dns_gethostbyname4_r (const char *name, struct gaih_addrtuple **pat,
 	name = cp;
     }
 
+  int anslen = 2048;
   union
   {
     querybuf *buf;
     u_char *ptr;
   } host_buffer;
   querybuf *orig_host_buffer;
-  host_buffer.buf = orig_host_buffer = (querybuf *) alloca (2048);
+  host_buffer.buf = orig_host_buffer = (querybuf *) alloca (anslen);
   u_char *ans2p = NULL;
   int nans2p = 0;
   int resplen2 = 0;
@@ -312,7 +313,7 @@ _nss_dns_gethostbyname4_r (const char *name, struct gaih_addrtuple **pat,
   int olderr = errno;
   enum nss_status status;
   int n = __libc_res_nsearch (&_res, name, C_IN, T_UNSPEC,
-			      host_buffer.buf->buf, 2048, &host_buffer.ptr,
+			      host_buffer.buf->buf, anslen, &host_buffer.ptr,
 			      &ans2p, &nans2p, &resplen2);
   if (n < 0)
     {
@@ -352,6 +353,13 @@ _nss_dns_gethostbyname4_r (const char *name, struct gaih_addrtuple **pat,
 			  resplen2, name, pat, buffer, buflen,
 			  errnop, herrnop, ttlp);
 
+  /* Check whether ans2p was separately allocated.  */
+  if (host_buffer.buf != orig_host_buffer)
+    anslen = MAXPACKET;
+  if (ans2p != NULL
+      && (ans2p < host_buffer.ptr || ans2p >= host_buffer.ptr + anslen))
+    free (ans2p);
+
   if (host_buffer.buf != orig_host_buffer)
     free (host_buffer.buf);