linux-kernel - Re: [syzbot] [net?] INFO: rcu detected stall in packet

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Date: Thu, 30 May 2024 19:57:26 +0800
From: Hillf Danton <hdanton@...a.com>
To: Vladimir Oltean <vladimir.oltean@....com>
Cc: syzbot <syzbot+a7d2b1d5d1af83035567@...kaller.appspotmail.com>,
	edumazet@...gle.com,
	linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org,
	radoslaw.zielonek@...il.com,
	syzkaller-bugs@...glegroups.com,
	vinicius.gomes@...el.com
Subject: Re: [syzbot] [net?] INFO: rcu detected stall in packet_release

On Thu, 30 May 2024 03:33:25 +0300 Vladimir Oltean <vladimir.oltean@....com>
> 
> What is the fact that you submitted only my patch 1/2 for syzbot testing
> supposed to prove? It is the second patch (2/2) that addresses what has
> been reported here;

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git  main

--- x/net/sched/sch_taprio.c
+++ y/net/sched/sch_taprio.c
@@ -1151,11 +1151,6 @@ static int parse_taprio_schedule(struct
 		list_for_each_entry(entry, &new->entries, list)
 			cycle = ktime_add_ns(cycle, entry->interval);
 
-		if (!cycle) {
-			NL_SET_ERR_MSG(extack, "'cycle_time' can never be 0");
-			return -EINVAL;
-		}
-
 		if (cycle < 0 || cycle > INT_MAX) {
 			NL_SET_ERR_MSG(extack, "'cycle_time' is too big");
 			return -EINVAL;
@@ -1164,6 +1159,11 @@ static int parse_taprio_schedule(struct
 		new->cycle_time = cycle;
 	}
 
+	if (new->cycle_time < new->num_entries * length_to_duration(q, ETH_ZLEN)) {
+		NL_SET_ERR_MSG(extack, "'cycle_time' is too small");
+		return -EINVAL;
+	}
+
 	taprio_calculate_gate_durations(q, new);
 
 	return 0;
@@ -1848,6 +1848,9 @@ static int taprio_change(struct Qdisc *s
 	}
 	q->flags = taprio_flags;
 
+	/* Needed for length_to_duration() during netlink attribute parsing */
+	taprio_set_picos_per_byte(dev, q);
+
 	err = taprio_parse_mqprio_opt(dev, mqprio, extack, q->flags);
 	if (err < 0)
 		return err;
@@ -1907,7 +1910,6 @@ static int taprio_change(struct Qdisc *s
 	if (err < 0)
 		goto free_sched;
 
-	taprio_set_picos_per_byte(dev, q);
 	taprio_update_queue_max_sdu(q, new_admin, stab);
 
 	if (FULL_OFFLOAD_IS_ENABLED(q->flags))
--