path: root/net
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authorXin Long <lucien.xin@gmail.com>2019-03-08 14:50:54 +0800
committerDavid S. Miller <davem@davemloft.net>2019-03-08 10:50:34 -0800
commitee60ad219f5c7c4fb2f047f88037770063ef785f (patch)
treec431df6195f7b5a4dc61ecc0d57eb16e022c7532 /net
parentnet/hsr: fix possible crash in add_timer() (diff)
route: set the deleted fnhe fnhe_daddr to 0 in ip_del_fnhe to fix a race
The race occurs in __mkroute_output() when 2 threads lookup a dst: CPU A CPU B find_exception() find_exception() [fnhe expires] ip_del_fnhe() [fnhe is deleted] rt_bind_exception() In rt_bind_exception() it will bind a deleted fnhe with the new dst, and this dst will get no chance to be freed. It causes a dev defcnt leak and consecutive dmesg warnings: unregister_netdevice: waiting for ethX to become free. Usage count = 1 Especially thanks Jon to identify the issue. This patch fixes it by setting fnhe_daddr to 0 in ip_del_fnhe() to stop binding the deleted fnhe with a new dst when checking fnhe's fnhe_daddr and daddr in rt_bind_exception(). It works as both ip_del_fnhe() and rt_bind_exception() are protected by fnhe_lock and the fhne is freed by kfree_rcu(). Fixes: deed49df7390 ("route: check and remove route cache when we get route") Signed-off-by: Jon Maxwell <jmaxwell37@gmail.com> Signed-off-by: Xin Long <lucien.xin@gmail.com> Reviewed-by: David Ahern <dsahern@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
1 files changed, 4 insertions, 0 deletions
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 8ca3642f0d9b..a5da63e5faa2 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1303,6 +1303,10 @@ static void ip_del_fnhe(struct fib_nh *nh, __be32 daddr)
if (fnhe->fnhe_daddr == daddr) {
rcu_assign_pointer(*fnhe_p, rcu_dereference_protected(
fnhe->fnhe_next, lockdep_is_held(&fnhe_lock)));
+ /* set fnhe_daddr to 0 to ensure it won't bind with
+ * new dsts in rt_bind_exception().
+ */
+ fnhe->fnhe_daddr = 0;
kfree_rcu(fnhe, rcu);