ipv6: Clamp reported valid_lft to a minimum of 0

Since addresses are only revalidated every 2 minutes, the reported
valid_lft can underflow shortly before the address is deleted.
Clamp it to a minimum of 0, as for prefered_lft.

Reported-by: Piotr Lewandowski <piotr.lewandowski@gmail.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 2 deletions

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index c20a7c260a8f..51a273fe3d21 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -3495,8 +3495,12 @@ static int inet6_fill_ifaddr(struct sk_buff *skb, struct inet6_ifaddr *ifa,
                                 preferred -= tval;
                         else
                                 preferred = 0;
-                        if (valid != INFINITY_LIFE_TIME)
-                                valid -= tval;
+                        if (valid != INFINITY_LIFE_TIME) {
+                                if (valid > tval)
+                                        valid -= tval;
+                                else
+                                        valid = 0;
+                        }
                 }
         } else {
                 preferred = INFINITY_LIFE_TIME;