From c9a82bec02c339cdda99b37c5e62b3b71fc4209c Mon Sep 17 00:00:00 2001
From: Vlad Buslov <vladbu@nvidia.com>
Date: Mon, 12 Jun 2023 11:34:26 +0200
Subject: [PATCH] net/sched: cls_api: Fix lockup on flushing explicitly created
chain
Mingshuai Ren reports:
When a new chain is added by using tc, one soft lockup alarm will be
generated after delete the prio 0 filter of the chain. To reproduce
the problem, perform the following steps:
(1) tc qdisc add dev eth0 root handle 1: htb default 1
(2) tc chain add dev eth0
(3) tc filter del dev eth0 chain 0 parent 1: prio 0
(4) tc filter add dev eth0 chain 0 parent 1:
Fix the issue by accounting for additional reference to chains that are
explicitly created by RTM_NEWCHAIN message as opposed to implicitly by
RTM_NEWTFILTER message.
Fixes: 726d061286ce ("net: sched: prevent insertion of new classifiers during chain flush")
Reported-by: Mingshuai Ren <renmingshuai@huawei.com>
Closes: https://lore.kernel.org/lkml/87legswvi3.fsf@nvidia.com/T/
Signed-off-by: Vlad Buslov <vladbu@nvidia.com>
Link: https://lore.kernel.org/r/20230612093426.2867183-1-vladbu@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
net/sched/cls_api.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index c877a6343fd47..a193cc7b32418 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -657,8 +657,8 @@ static void __tcf_chain_put(struct tcf_chain *chain, bool by_act,
{
struct tcf_block *block = chain->block;
const struct tcf_proto_ops *tmplt_ops;
+ unsigned int refcnt, non_act_refcnt;
bool free_block = false;
- unsigned int refcnt;
void *tmplt_priv;
mutex_lock(&block->lock);
@@ -678,13 +678,15 @@ static void __tcf_chain_put(struct tcf_chain *chain, bool by_act,
* save these to temporary variables.
*/
refcnt = --chain->refcnt;
+ non_act_refcnt = refcnt - chain->action_refcnt;
tmplt_ops = chain->tmplt_ops;
tmplt_priv = chain->tmplt_priv;
- /* The last dropped non-action reference will trigger notification. */
- if (refcnt - chain->action_refcnt == 0 && !by_act) {
- tc_chain_notify_delete(tmplt_ops, tmplt_priv, chain->index,
- block, NULL, 0, 0, false);
+ if (non_act_refcnt == chain->explicitly_created && !by_act) {
+ if (non_act_refcnt == 0)
+ tc_chain_notify_delete(tmplt_ops, tmplt_priv,
+ chain->index, block, NULL, 0, 0,
+ false);
/* Last reference to chain, no need to lock. */
chain->flushing = false;
}
--
2.30.2