netdev - Re: [PATCH net] net: hsr: prevent NULL pointer dereference in hsr_proxy

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Message-ID: <20240910191517.0eeaa132@kernel.org>
Date: Tue, 10 Sep 2024 19:15:17 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Lukasz Majewski <lukma@...x.de>
Cc: Jeongjun Park <aha310510@...il.com>, davem@...emloft.net,
 edumazet@...gle.com, pabeni@...hat.com, horms@...nel.org,
 ricardo@...liere.net, m-karicheri2@...com, n.zhandarovich@...tech.ru,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 syzbot+02a42d9b1bd395cbcab4@...kaller.appspotmail.com
Subject: Re: [PATCH net] net: hsr: prevent NULL pointer dereference in
 hsr_proxy_announce()

On Mon, 9 Sep 2024 10:58:22 +0200 Lukasz Majewski wrote:
> > In the function hsr_proxy_annouance() added in the previous commit 
> > 5f703ce5c981 ("net: hsr: Send supervisory frames to HSR network 
> > with ProxyNodeTable data"), the return value of the
> > hsr_port_get_hsr() function is not checked to be a NULL pointer,
> > which causes a NULL pointer dereference.  
> 
> Thank you for your patch.
> 
> The code in hsr_proxy_announcement() is _only_ executed (the timer is
> configured to trigger this function) when hsr->redbox is set, which
> means that somebody has called earlier iproute2 command:
> 
> ip link add name hsr1 type hsr slave1 lan4 slave2 lan5 interlink lan3
> supervision 45 version 1

Are you trying to say the patch is correct or incorrect?
The structs have no refcounting - should the timers be deleted with
_sync() inside hsr_check_announce()?