Properly fix memory leak in _nss_dns_gethostbyname4_r with big DNS answer

Instead of trying to guess whether the second buffer needs to be freed
set a flag at the place it is allocated

3 files changed, 13 insertions, 16 deletions

diff --git a/resolv/nss_dns/dns-canon.c b/resolv/nss_dns/dns-canon.c
index a9db232..e8c112c 100644
--- a/resolv/nss_dns/dns-canon.c
+++ b/resolv/nss_dns/dns-canon.c
@@ -62,7 +62,7 @@ _nss_dns_getcanonname_r (const char *name, char *buffer, size_t buflen,
     {
       int r = __libc_res_nquery (&_res, name, ns_c_in, qtypes[i],
 				 buf, sizeof (buf), &ansp.ptr, NULL, NULL,
-				 NULL);
+				 NULL, NULL);
       if (r > 0)
 	{
 	  /* We need to decode the response.  Just one question record.
diff --git a/resolv/nss_dns/dns-host.c b/resolv/nss_dns/dns-host.c
index 47f998c..a5f2c0a 100644
--- a/resolv/nss_dns/dns-host.c
+++ b/resolv/nss_dns/dns-host.c
@@ -190,7 +190,7 @@ _nss_dns_gethostbyname3_r (const char *name, int af, struct hostent *result,
   host_buffer.buf = orig_host_buffer = (querybuf *) alloca (1024);
 
   n = __libc_res_nsearch (&_res, name, C_IN, type, host_buffer.buf->buf,
-			  1024, &host_buffer.ptr, NULL, NULL, NULL);
+			  1024, &host_buffer.ptr, NULL, NULL, NULL, NULL);
   if (n < 0)
     {
       switch (errno)
@@ -225,7 +225,7 @@ _nss_dns_gethostbyname3_r (const char *name, int af, struct hostent *result,
 	n = __libc_res_nsearch (&_res, name, C_IN, T_A, host_buffer.buf->buf,
 				host_buffer.buf != orig_host_buffer
 				? MAXPACKET : 1024, &host_buffer.ptr,
-				NULL, NULL, NULL);
+				NULL, NULL, NULL, NULL);
 
       if (n < 0)
 	{
@@ -298,23 +298,23 @@ _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 (anslen);
+  host_buffer.buf = orig_host_buffer = (querybuf *) alloca (2048);
   u_char *ans2p = NULL;
   int nans2p = 0;
   int resplen2 = 0;
+  int ans2p_malloced = 0;
 
   int olderr = errno;
   enum nss_status status;
   int n = __libc_res_nsearch (&_res, name, C_IN, T_UNSPEC,
-			      host_buffer.buf->buf, anslen, &host_buffer.ptr,
-			      &ans2p, &nans2p, &resplen2);
+			      host_buffer.buf->buf, 2048, &host_buffer.ptr,
+			      &ans2p, &nans2p, &resplen2, &ans2p_malloced);
   if (n >= 0)
     {
       status = gaih_getanswer (host_buffer.buf, n, (const querybuf *) ans2p,
@@ -351,10 +351,7 @@ _nss_dns_gethostbyname4_r (const char *name, struct gaih_addrtuple **pat,
     }
 
   /* 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))
+  if (ans2p_malloced)
     free (ans2p);
 
   if (host_buffer.buf != orig_host_buffer)
@@ -465,7 +462,7 @@ _nss_dns_gethostbyaddr2_r (const void *addr, socklen_t len, int af,
 	  strcpy (qp, "].ip6.arpa");
 	  n = __libc_res_nquery (&_res, qbuf, C_IN, T_PTR,
 				 host_buffer.buf->buf, 1024, &host_buffer.ptr,
-				 NULL, NULL, NULL);
+				 NULL, NULL, NULL, NULL);
 	  if (n >= 0)
 	    goto got_it_already;
 	}
@@ -486,14 +483,14 @@ _nss_dns_gethostbyaddr2_r (const void *addr, socklen_t len, int af,
     }
 
   n = __libc_res_nquery (&_res, qbuf, C_IN, T_PTR, host_buffer.buf->buf,
-			 1024, &host_buffer.ptr, NULL, NULL, NULL);
+			 1024, &host_buffer.ptr, NULL, NULL, NULL, NULL);
   if (n < 0 && af == AF_INET6 && (_res.options & RES_NOIP6DOTINT) == 0)
     {
       strcpy (qp, "ip6.int");
       n = __libc_res_nquery (&_res, qbuf, C_IN, T_PTR, host_buffer.buf->buf,
 			     host_buffer.buf != orig_host_buffer
 			     ? MAXPACKET : 1024, &host_buffer.ptr,
-			     NULL, NULL, NULL);
+			     NULL, NULL, NULL, NULL);
     }
   if (n < 0)
     {
diff --git a/resolv/nss_dns/dns-network.c b/resolv/nss_dns/dns-network.c
index b8aee21..0a77c8b 100644
--- a/resolv/nss_dns/dns-network.c
+++ b/resolv/nss_dns/dns-network.c
@@ -129,7 +129,7 @@ _nss_dns_getnetbyname_r (const char *name, struct netent *result,
   net_buffer.buf = orig_net_buffer = (querybuf *) alloca (1024);
 
   anslen = __libc_res_nsearch (&_res, qbuf, C_IN, T_PTR, net_buffer.buf->buf,
-			       1024, &net_buffer.ptr, NULL, NULL, NULL);
+			       1024, &net_buffer.ptr, NULL, NULL, NULL, NULL);
   if (anslen < 0)
     {
       /* Nothing found.  */
@@ -205,7 +205,7 @@ _nss_dns_getnetbyaddr_r (uint32_t net, int type, struct netent *result,
   net_buffer.buf = orig_net_buffer = (querybuf *) alloca (1024);
 
   anslen = __libc_res_nquery (&_res, qbuf, C_IN, T_PTR, net_buffer.buf->buf,
-			      1024, &net_buffer.ptr, NULL, NULL, NULL);
+			      1024, &net_buffer.ptr, NULL, NULL, NULL, NULL);
   if (anslen < 0)
     {
       /* Nothing found.  */