From: Vlad Buslov <vladbu@mellanox.com>
Date: Mon, 24 Sep 2018 19:22:52 +0300
Subject: net: sched: add helper function to take reference to Qdisc
Patch-mainline: v4.20-rc1
Git-commit: 9d7e82cec35c027756ec97e274f878251f271181
References: bsc#1196973 CVE-2021-39713
Implement function to take reference to Qdisc that relies on rcu read lock
instead of rtnl mutex. Function only takes reference to Qdisc if reference
counter isn't zero. Intended to be used by unlocked cls API.
Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
include/net/sch_generic.h | 13 +++++++++++++
1 file changed, 13 insertions(+)
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -114,6 +114,19 @@ static inline void qdisc_refcount_inc(st
refcount_inc(&qdisc->refcnt);
}
+/* Intended to be used by unlocked users, when concurrent qdisc release is
+ * possible.
+ */
+
+static inline struct Qdisc *qdisc_refcount_inc_nz(struct Qdisc *qdisc)
+{
+ if (qdisc->flags & TCQ_F_BUILTIN)
+ return qdisc;
+ if (refcount_inc_not_zero(&qdisc->refcnt))
+ return qdisc;
+ return NULL;
+}
+
static inline bool qdisc_is_running(struct Qdisc *qdisc)
{
if (qdisc->flags & TCQ_F_NOLOCK)