linux-kernel - Re: [PATCH net,v2] rtnetlink: fix possible deadlock in team_port_change

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Message-ID: <Zqrv64570Zp9HaxZ@Laptop-X1>
Date: Thu, 1 Aug 2024 10:16:11 +0800
From: Hangbin Liu <liuhangbin@...il.com>
To: Jeongjun Park <aha310510@...il.com>
Cc: jiri@...nulli.us, davem@...emloft.net, edumazet@...gle.com,
	kuba@...nel.org, pabeni@...hat.com, nicolas.dichtel@...nd.com,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	syzbot+44623300f057a28baf1e@...kaller.appspotmail.com,
	syzbot+b668da2bc4cb9670bf58@...kaller.appspotmail.com
Subject: Re: [PATCH net,v2] rtnetlink: fix possible deadlock in
 team_port_change_check

On Thu, Aug 01, 2024 at 12:09:40AM +0900, Jeongjun Park wrote:
> In do_setlink() , do_set_master() is called when dev->flags does not have
> the IFF_UP flag set, so 'team->lock' is acquired and dev_open() is called,
> which generates the NETDEV_UP event. This causes a deadlock as it tries to
> acquire 'team->lock' again.
> 
> To solve this, we need to unlock 'team->lock' before calling dev_open()
> in team_port_add() and then reacquire the lock when dev_open() returns.
> Since the implementation acquires the lock in advance when the team
> structure is used inside dev_open(), data races will not occur even if it
> is briefly unlocked.
> 
> 
> Reported-by: syzbot+b668da2bc4cb9670bf58@...kaller.appspotmail.com
> Fixes: ec4ffd100ffb ("Revert "net: rtnetlink: Enslave device before bringing it up"")

The fixes tag shouldn't be ec4ffd100ffb, as the issue exists before
ec4ffd100ffb. I think it should be

3d249d4ca7d0 ("net: introduce ethernet teaming device")

Jiri, what do you think?

Thanks
Hangbin