1 files changed, 33 insertions, 16 deletions

diff --git a/networking/udhcp/dhcpd.c b/networking/udhcp/dhcpd.c
index 093239536..19f94a2d7 100644
--- a/networking/udhcp/dhcpd.c
+++ b/networking/udhcp/dhcpd.c
@@ -853,6 +853,9 @@ int udhcpd_main(int argc UNUSED_PARAM, char **argv)
         /* Would rather not do read_config before daemonization -
          * otherwise NOMMU machines will parse config twice */
         read_config(argv[0] ? argv[0] : DHCPD_CONF_FILE);
+        /* prevent poll timeout overflow */
+        if (server_config.auto_time > INT_MAX / 1000)
+                server_config.auto_time = INT_MAX / 1000;
 
         /* Make sure fd 0,1,2 are open */
         bb_sanitize_stdio();
@@ -914,21 +917,31 @@ int udhcpd_main(int argc UNUSED_PARAM, char **argv)
                 }
 
                 udhcp_sp_fd_set(pfds, server_socket);
-                tv = timeout_end - monotonic_sec();
-                retval = 0;
-                if (!server_config.auto_time || tv > 0) {
-                        retval = poll(pfds, 2, server_config.auto_time ? tv * 1000 : -1);
-                }
-                if (retval == 0) {
-                        write_leases();
-                        goto continue_with_autotime;
+
+ new_tv:
+                tv = -1;
+                if (server_config.auto_time) {
+                        tv = timeout_end - monotonic_sec();
+                        if (tv <= 0) {
+ write_leases:
+                                write_leases();
+                                goto continue_with_autotime;
+                        }
+                        tv *= 1000;
                 }
-                if (retval < 0 && errno != EINTR) {
-                        log1("error on select");
-                        continue;
+
+                /* Block here waiting for either signal or packet */
+                retval = poll(pfds, 2, tv);
+                if (retval <= 0) {
+                        if (retval == 0)
+                                goto write_leases;
+                        if (errno == EINTR)
+                                goto new_tv;
+                        /* < 0 and not EINTR: should not happen */
+                        bb_perror_msg_and_die("poll");
                 }
 
-                switch (udhcp_sp_read(pfds)) {
+                if (pfds[0].revents) switch (udhcp_sp_read()) {
                 case SIGUSR1:
                         bb_error_msg("received %s", "SIGUSR1");
                         write_leases();
@@ -938,12 +951,16 @@ int udhcpd_main(int argc UNUSED_PARAM, char **argv)
                         bb_error_msg("received %s", "SIGTERM");
                         write_leases();
                         goto ret0;
-                case 0: /* no signal: read a packet */
-                        break;
-                default: /* signal or error (probably EINTR): back to select */
-                        continue;
                 }
 
+                /* Is it a packet? */
+                if (!pfds[1].revents)
+                        continue; /* no */
+
+                /* Note: we do not block here, we block on poll() instead.
+                 * Blocking here would prevent SIGTERM from working:
+                 * socket read inside this call is restarted on caught signals.
+                 */
                 bytes = udhcp_recv_kernel_packet(&packet, server_socket);
                 if (bytes < 0) {
                         /* bytes can also be -2 ("bad packet data") */