From: Ben Pfaff <blp@nicira.com>
Date: Fri, 9 Jan 2009 00:47:01 +0000 (-0800)
Subject: dhcp-client: Don't report long time to expiration after lease expires.
X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0b76831f0bac4f50594a16a16c68217d0f8d48d6;p=openvswitch

dhcp-client: Don't report long time to expiration after lease expires.

There is a race between time advancing past the lease expiration time
and actually transitioning to the expired state.  Fix this race.

Found by Chris Eagle via Fortify.
---

diff --git a/lib/dhcp-client.c b/lib/dhcp-client.c
index 919bc31d..4c12b4eb 100644
--- a/lib/dhcp-client.c
+++ b/lib/dhcp-client.c
@@ -356,7 +356,12 @@ dhclient_get_state_elapsed(const struct dhclient *cli)
 unsigned int
 dhclient_get_lease_remaining(const struct dhclient *cli)
 {
-    return dhclient_is_bound(cli) ? cli->lease_expiration - time_now() : 0;
+    if (dhclient_is_bound(cli)) {
+        time_t now = time_now();
+        return cli->lease_expiration > now ? cli->lease_expiration - now : 0;
+    } else {
+        return 0;
+    }
 }
 
 /* If 'cli' is bound to an IP address, returns that IP address; otherwise,