ipv6: avoid wraparound for expired preferred lifetime

Avoid showing wrong high values when the preferred lifetime of an address
is expired.

Signed-off-by: Jens Rosenboom <me@jayr.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 1 deletions

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 8c1e86afbbf5..3883b4036a74 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -3362,7 +3362,10 @@ static int inet6_fill_ifaddr(struct sk_buff *skb, struct inet6_ifaddr *ifa,
                 valid = ifa->valid_lft;
                 if (preferred != INFINITY_LIFE_TIME) {
                         long tval = (jiffies - ifa->tstamp)/HZ;
-                        preferred -= tval;
+                        if (preferred > tval)
+                                preferred -= tval;
+                        else
+                                preferred = 0;
                         if (valid != INFINITY_LIFE_TIME)
                                 valid -= tval;
                 }