linux-kernel - [PATCH] net/sched: use spin_lock_bh() on &gact->tcf

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Message-Id: <20230926182625.72475-1-dg573847474@gmail.com>
Date:   Tue, 26 Sep 2023 18:26:25 +0000
From:   Chengfeng Ye <dg573847474@...il.com>
To:     jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Chengfeng Ye <dg573847474@...il.com>
Subject: [PATCH] net/sched: use spin_lock_bh() on &gact->tcf_lock

I find tcf_gate_act() acquires &gact->tcf_lock without disable
bh explicitly, as gact->tcf_lock is acquired inside timer under
softirq context, if tcf_gate_act() is not called with bh disable
by default or under softirq context(which I am not sure as I cannot
find corresponding documentation), then it could be the following 
deadlocks.

tcf_gate_act()
--> spin_loc(&gact->tcf_lock)
<interrupt>
   --> gate_timer_func()
   --> spin_lock(&gact->tcf_lock)

Signed-off-by: Chengfeng Ye <dg573847474@...il.com>
---
 net/sched/act_gate.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/net/sched/act_gate.c b/net/sched/act_gate.c
index c9a811f4c7ee..b82daf7401a5 100644
--- a/net/sched/act_gate.c
+++ b/net/sched/act_gate.c
@@ -124,25 +124,25 @@ TC_INDIRECT_SCOPE int tcf_gate_act(struct sk_buff *skb,
 	tcf_lastuse_update(&gact->tcf_tm);
 	tcf_action_update_bstats(&gact->common, skb);
 
-	spin_lock(&gact->tcf_lock);
+	spin_lock_bh(&gact->tcf_lock);
 	if (unlikely(gact->current_gate_status & GATE_ACT_PENDING)) {
-		spin_unlock(&gact->tcf_lock);
+		spin_unlock_bh(&gact->tcf_lock);
 		return action;
 	}
 
 	if (!(gact->current_gate_status & GATE_ACT_GATE_OPEN)) {
-		spin_unlock(&gact->tcf_lock);
+		spin_unlock_bh(&gact->tcf_lock);
 		goto drop;
 	}
 
 	if (gact->current_max_octets >= 0) {
 		gact->current_entry_octets += qdisc_pkt_len(skb);
 		if (gact->current_entry_octets > gact->current_max_octets) {
-			spin_unlock(&gact->tcf_lock);
+			spin_unlock_bh(&gact->tcf_lock);
 			goto overlimit;
 		}
 	}
-	spin_unlock(&gact->tcf_lock);
+	spin_unlock_bh(&gact->tcf_lock);
 
 	return action;
 
-- 
2.17.1