[BZ #5375]

	* resolv/res_hconf.c (_res_hconf_reorder_addrs): Fix locking when
	initializing interface list.

diff --git a/ChangeLog b/ChangeLog
index 84769fb..50729fd 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2007-11-22  Ulrich Drepper  <drepper@redhat.com>
 
+       [BZ #5375]
+       * resolv/res_hconf.c (_res_hconf_reorder_addrs): Fix locking when
+       initializing interface list.
+
        [BZ #5378]
        * nis/nss_compat/compat-initgroups.c (getgrent_next_nss): Don't
        use result of nss_getgrgid_r if nothing was found.  For other

diff --git a/resolv/res_hconf.c b/resolv/res_hconf.c
index c53b809..25f7397 100644 (file)
--- a/resolv/res_hconf.c
+++ b/resolv/res_hconf.c
@@ -377,9 +377,6 @@ static struct netaddr
   } u;
 } *ifaddrs);
 
-/* We need to protect the dynamic buffer handling.  */
-__libc_lock_define_initialized (static, lock);
-
 /* Reorder addresses returned in a hostent such that the first address
    is an address on the local subnet, if there is such an address.
    Otherwise, nothing is changed.
@@ -393,6 +390,8 @@ _res_hconf_reorder_addrs (struct hostent *hp)
   int i, j;
   /* Number of interfaces.  */
   static int num_ifs = -1;
+  /* We need to protect the dynamic buffer handling.  */
+  __libc_lock_define_initialized (static, lock);
 
   /* Only reorder if we're supposed to.  */
   if ((_res_hconf.flags & HCONF_FLAG_REORDER) == 0)
@@ -411,8 +410,6 @@ _res_hconf_reorder_addrs (struct hostent *hp)
 
       /* Initialize interface table.  */
 
-      num_ifs = 0;
-
       /* The SIOCGIFNETMASK ioctl will only work on an AF_INET socket.  */
       sd = __socket (AF_INET, SOCK_DGRAM, 0);
       if (sd < 0)
@@ -421,45 +418,56 @@ _res_hconf_reorder_addrs (struct hostent *hp)
       /* Get lock.  */
       __libc_lock_lock (lock);
 
-      /* Get a list of interfaces.  */
-      __ifreq (&ifr, &num, sd);
-      if (!ifr)
-       goto cleanup;
+      /* Recheck, somebody else might have done the work by done.  */
+      if (num_ifs <= 0)
+       {
+         int new_num_ifs = 0;
 
-      ifaddrs = malloc (num * sizeof (ifaddrs[0]));
-      if (!ifaddrs)
-       goto cleanup1;
+         /* Get a list of interfaces.  */
+         __ifreq (&ifr, &num, sd);
+         if (!ifr)
+           goto cleanup;
 
-      /* Copy usable interfaces in ifaddrs structure.  */
-      for (cur_ifr = ifr, i = 0; i < num; cur_ifr = __if_nextreq (cur_ifr), ++i)
-       {
-         if (cur_ifr->ifr_addr.sa_family != AF_INET)
-           continue;
+         ifaddrs = malloc (num * sizeof (ifaddrs[0]));
+         if (!ifaddrs)
+           goto cleanup1;
 
-         ifaddrs[num_ifs].addrtype = AF_INET;
-         ifaddrs[num_ifs].u.ipv4.addr =
-           ((struct sockaddr_in *) &cur_ifr->ifr_addr)->sin_addr.s_addr;
+         /* Copy usable interfaces in ifaddrs structure.  */
+         for (cur_ifr = ifr, i = 0; i < num;
+              cur_ifr = __if_nextreq (cur_ifr), ++i)
+           {
+             if (cur_ifr->ifr_addr.sa_family != AF_INET)
+               continue;
 
-         if (__ioctl (sd, SIOCGIFNETMASK, cur_ifr) < 0)
-           continue;
+             ifaddrs[new_num_ifs].addrtype = AF_INET;
+             ifaddrs[new_num_ifs].u.ipv4.addr =
+               ((struct sockaddr_in *) &cur_ifr->ifr_addr)->sin_addr.s_addr;
 
-         ifaddrs[num_ifs].u.ipv4.mask =
-           ((struct sockaddr_in *) &cur_ifr->ifr_netmask)->sin_addr.s_addr;
+             if (__ioctl (sd, SIOCGIFNETMASK, cur_ifr) < 0)
+               continue;
 
-         /* Now we're committed to this entry.  */
-         ++num_ifs;
-       }
-      /* Just keep enough memory to hold all the interfaces we want.  */
-      ifaddrs = realloc (ifaddrs, num_ifs * sizeof (ifaddrs[0]));
-      assert (ifaddrs != NULL);
+             ifaddrs[new_num_ifs].u.ipv4.mask =
+               ((struct sockaddr_in *) &cur_ifr->ifr_netmask)->sin_addr.s_addr;
 
-    cleanup1:
-      __if_freereq (ifr, num);
+             /* Now we're committed to this entry.  */
+             ++new_num_ifs;
+           }
+         /* Just keep enough memory to hold all the interfaces we want.  */
+         ifaddrs = realloc (ifaddrs, new_num_ifs * sizeof (ifaddrs[0]));
+         assert (ifaddrs != NULL);
+
+       cleanup1:
+         __if_freereq (ifr, num);
+
+       cleanup:
+         /* Release lock, preserve error value, and close socket.  */
+         save = errno;
+
+         num_ifs = new_num_ifs;
+
+         __libc_lock_unlock (lock);
+       }
 
-    cleanup:
-      /* Release lock, preserve error value, and close socket.  */
-      save = errno;
-      __libc_lock_unlock (lock);
       __close (sd);
     }