ipv6: protect flow label renew against GC

Take ip6_fl_lock before to read and update
a label.

v2: protect only the relevant code

Reported-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: Florent Fourcot <florent.fourcot@enst-bretagne.fr>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 0 deletions

diff --git a/net/ipv6/ip6_flowlabel.c b/net/ipv6/ip6_flowlabel.c
index 5f10b0d0bca5..98fdcc6f51b1 100644
--- a/net/ipv6/ip6_flowlabel.c
+++ b/net/ipv6/ip6_flowlabel.c
@@ -345,6 +345,8 @@ static int fl6_renew(struct ip6_flowlabel *fl, unsigned long linger, unsigned lo
         expires = check_linger(expires);
         if (!expires)
                 return -EPERM;
+
+        spin_lock_bh(&ip6_fl_lock);
         fl->lastuse = jiffies;
         if (time_before(fl->linger, linger))
                 fl->linger = linger;
@@ -352,6 +354,8 @@ static int fl6_renew(struct ip6_flowlabel *fl, unsigned long linger, unsigned lo
                 expires = fl->linger;
         if (time_before(fl->expires, fl->lastuse + expires))
                 fl->expires = fl->lastuse + expires;
+        spin_unlock_bh(&ip6_fl_lock);
+
         return 0;
 }