From: Vlad Buslov vladbu@nvidia.com
[ Upstream commit c9a82bec02c339cdda99b37c5e62b3b71fc4209c ]
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 Signed-off-by: Sasha Levin sashal@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; }