netdev - Re: [PATCH net,v2] team: fix possible deadlock in team_port_change

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Message-ID: <Zq0akdhiSeoiOLsY@nanopsycho.orion>
Date: Fri, 2 Aug 2024 19:42:41 +0200
From: Jiri Pirko <jiri@...nulli.us>
To: Jeongjun Park <aha310510@...il.com>
Cc: edumazet@...gle.com, davem@...emloft.net, kuba@...nel.org,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	pabeni@...hat.com,
	syzbot+b668da2bc4cb9670bf58@...kaller.appspotmail.com
Subject: Re: [PATCH net,v2] team: fix possible deadlock in
 team_port_change_check

Fri, Aug 02, 2024 at 06:25:31PM CEST, aha310510@...il.com wrote:
>Eric Dumazet wrote:
>>
>> On Fri, Aug 2, 2024 at 5:00 PM Jeongjun Park <aha310510@...il.com> wrote:
>> >

[..]

>@@ -2501,6 +2470,11 @@ int team_nl_options_get_doit(struct sk_buff *skb, struct genl_info *info)
> 	int err;
> 	LIST_HEAD(sel_opt_inst_list);
> 
>+	if (!rtnl_is_locked()) {

This is completely wrong, other thread may hold the lock.


>+		rtnl_lock();

NACK! I wrote it in the other thread. Don't take rtnl for get options
command. It is used for repeated fetch of stats. It's read only. Should
be converted to RCU.

Why are you so obsessed by this hypothetical syzcaller bug? Are you
hitting this in real? If not, please let it go. I will fix it myself
when I find some spare cycles.




>+		team->rtnl_locked = true;
>+	}
>+
> 	team = team_nl_team_get(info);
> 	if (!team)
> 		return -EINVAL;
>@@ -2513,6 +2487,11 @@ int team_nl_options_get_doit(struct sk_buff *skb, struct genl_info *info)
> 
> 	team_nl_team_put(team);
> 
>+	if (team->rtnl_locked) {
>+		team->rtnl_locked = false;
>+		rtnl_unlock();
>+	}
>+
> 	return err;
> }
> 

[..]