resolv: Report allocation errors in __res_vinit

ChangeLog

@@ -1,3 +1,15 @@
+2017-06-19  Florian Weimer  <fweimer@redhat.com>
+
+	* resolv/res_init.c (res_vinit_1): New function.
+	(__res_vinit): Call it.  Handle file open and memory allocation
+	failures.
+	* resolv/nss_dns/dns-host.c (_nss_dns_gethostbyname3_r): Propagate
+	erno from __res_maybe_init failure.
+	(_nss_dns_gethostbyname4_r): Likewise.
+	(_nss_dns_gethostbyaddr2_r): Likewise.
+	* resolv/nss_dns/dns-network.c (_nss_dns_getnetbyname_r): Likewise.
+	(_nss_dns_getnetbyaddr_r): Likewise.
+
 2017-06-19  Florian Weimer  <fweimer@redhat.com>
 
 	* resolv/res_init.c: Reformat to GNU style.

resolv/nss_dns/dns-host.c

@@ -164,7 +164,11 @@ _nss_dns_gethostbyname3_r (const char *name, int af, struct hostent *result,
   enum nss_status status;
 
   if (__res_maybe_init (&_res, 0) == -1)
-    return NSS_STATUS_UNAVAIL;
+    {
+      *errnop = errno;
+      *h_errnop = NETDB_INTERNAL;
+      return NSS_STATUS_UNAVAIL;
+    }
 
   switch (af) {
   case AF_INET:
@@ -289,7 +293,11 @@ _nss_dns_gethostbyname4_r (const char *name, struct gaih_addrtuple **pat,
 			   int *herrnop, int32_t *ttlp)
 {
   if (__res_maybe_init (&_res, 0) == -1)
-    return NSS_STATUS_UNAVAIL;
+    {
+      *errnop = errno;
+      *herrnop = NETDB_INTERNAL;
+      return NSS_STATUS_UNAVAIL;
+    }
 
   /*
    * if there aren't any dots, it could be a user-level alias.
@@ -416,7 +424,11 @@ _nss_dns_gethostbyaddr2_r (const void *addr, socklen_t len, int af,
  host_data = (struct host_data *) buffer;
 
   if (__res_maybe_init (&_res, 0) == -1)
-    return NSS_STATUS_UNAVAIL;
+    {
+      *errnop = errno;
+      *h_errnop = NETDB_INTERNAL;
+      return NSS_STATUS_UNAVAIL;
+    }
 
   if (af == AF_INET6 && len == IN6ADDRSZ
       && (memcmp (uaddr, mapped, sizeof mapped) == 0

resolv/nss_dns/dns-network.c

@@ -116,7 +116,11 @@ _nss_dns_getnetbyname_r (const char *name, struct netent *result,
   enum nss_status status;
 
   if (__res_maybe_init (&_res, 0) == -1)
-    return NSS_STATUS_UNAVAIL;
+    {
+      *errnop = errno;
+      *herrnop = NETDB_INTERNAL;
+      return NSS_STATUS_UNAVAIL;
+    }
 
   net_buffer.buf = orig_net_buffer = (querybuf *) alloca (1024);
 
@@ -166,7 +170,11 @@ _nss_dns_getnetbyaddr_r (uint32_t net, int type, struct netent *result,
     return NSS_STATUS_UNAVAIL;
 
   if (__res_maybe_init (&_res, 0) == -1)
-    return NSS_STATUS_UNAVAIL;
+    {
+      *errnop = errno;
+      *herrnop = NETDB_INTERNAL;
+      return NSS_STATUS_UNAVAIL;
+    }
 
   net2 = (u_int32_t) net;
   for (cnt = 4; net2 != 0; net2 >>= 8)

resolv/res_init.c

@@ -100,6 +100,7 @@
 #include <sys/time.h>
 #include <sys/types.h>
 #include <inet/net-internal.h>
+#include <errno.h>
 
 static void res_setoptions (res_state, const char *, const char *);
 static uint32_t net_mask (struct in_addr);
@@ -121,14 +122,11 @@ is_sort_mask (char ch)
   return ch == '/' || ch == '&';
 }
 
-/* Set up default settings.  If the /etc/resolv.conf configuration
+/* Internal helper function for __res_vinit, to aid with resource
-   file exist, the values there will have precedence.  Otherwise, the
+   deallocation and error handling.  Return true on success, false on
-   server address is set to INADDR_LOOPBACK and the default domain
+   failure.  */
-   name comes from gethostname.  The RES_OPTIONS and LOCALDOMAIN
+static bool
-   environment variables can be used to override some settings.
+res_vinit_1 (res_state statp, bool preinit, FILE *fp)
-   Return 0 if completes successfully, -1 on error.  */
-int
-__res_vinit (res_state statp, int preinit)
 {
   char *cp, **pp;
   char buf[BUFSIZ];
@@ -203,7 +201,6 @@ __res_vinit (res_state statp, int preinit)
    && (line[sizeof (name) - 1] == ' '           \
        || line[sizeof (name) - 1] == '\t'))
 
-  FILE *fp = fopen (_PATH_RESCONF, "rce");
   if (fp != NULL)
     {
       /* No threads use this stream.  */
@@ -302,26 +299,26 @@ __res_vinit (res_state statp, int preinit)
                       struct sockaddr_in6 *sa6;
 
                       sa6 = malloc (sizeof (*sa6));
-                      if (sa6 != NULL)
+                      if (sa6 == NULL)
-                        {
+                        return -1;
-                          sa6->sin6_family = AF_INET6;
-                          sa6->sin6_port = htons (NAMESERVER_PORT);
-                          sa6->sin6_flowinfo = 0;
-                          sa6->sin6_addr = a6;
 
-                          sa6->sin6_scope_id = 0;
+                      sa6->sin6_family = AF_INET6;
-                          if (__glibc_likely (el != NULL))
+                      sa6->sin6_port = htons (NAMESERVER_PORT);
-                            /* Ignore errors, for backwards
+                      sa6->sin6_flowinfo = 0;
-                               compatibility.  */
+                      sa6->sin6_addr = a6;
-                            __inet6_scopeid_pton
-                              (&a6, el + 1, &sa6->sin6_scope_id);
 
-                          statp->nsaddr_list[nserv].sin_family = 0;
+                      sa6->sin6_scope_id = 0;
-                          statp->_u._ext.nsaddrs[nserv] = sa6;
+                      if (__glibc_likely (el != NULL))
-                          statp->_u._ext.nssocks[nserv] = -1;
+                        /* Ignore errors, for backwards
-                          have_serv6 = true;
+                           compatibility.  */
-                          nserv++;
+                        __inet6_scopeid_pton
-                        }
+                          (&a6, el + 1, &sa6->sin6_scope_id);
+
+                      statp->nsaddr_list[nserv].sin_family = 0;
+                      statp->_u._ext.nsaddrs[nserv] = sa6;
+                      statp->_u._ext.nssocks[nserv] = -1;
+                      have_serv6 = true;
+                      nserv++;
                     }
                 }
               continue;
@@ -410,6 +407,44 @@ __res_vinit (res_state statp, int preinit)
   return 0;
 }
 
+/* Set up default settings.  If the /etc/resolv.conf configuration
+   file exist, the values there will have precedence.  Otherwise, the
+   server address is set to INADDR_LOOPBACK and the default domain
+   name comes from gethostname.  The RES_OPTIONS and LOCALDOMAIN
+   environment variables can be used to override some settings.
+   Return 0 if completes successfully, -1 on error.  */
+int
+__res_vinit (res_state statp, int preinit)
+{
+  FILE *fp = fopen (_PATH_RESCONF, "rce");
+  if (fp == NULL)
+    switch (errno)
+      {
+      case EACCES:
+      case EISDIR:
+      case ELOOP:
+      case ENOENT:
+      case ENOTDIR:
+      case EPERM:
+        /* Ignore these errors.  They are persistent errors caused
+           by file system contents.  */
+        break;
+      default:
+        /* Other errors refer to resource allocation problems and
+           need to be handled by the application.  */
+        return -1;
+      }
+  if (!res_vinit_1 (statp, preinit, fp))
+    {
+      /* Deallocate the name server addresses which have been
+         allocated.  */
+      for (int n = 0; n < MAXNS; n++)
+        free (statp->_u._ext.nsaddrs[n]);
+      return -1;
+    }
+  return 0;
+}
+
 static void
 res_setoptions (res_state statp, const char *options, const char *source)
 {