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

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Message-ID: <20240911074325.55704611@kernel.org>
Date: Wed, 11 Sep 2024 07:43:25 -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 Wed, 11 Sep 2024 10:00:07 +0200 Lukasz Majewski wrote:
> > The structs have no refcounting - should the timers be deleted with
> > _sync() inside hsr_check_announce()?  
> 
> The timers don't need to be conditionally enabled (and removed) as we
> discussed it previously (as they only do useful work when they are
> configured and almost take no resources when declared during the
> driver probe).

My concern is admittedly quite theoretical, and perhaps completely
impossible given current RCU implementation. But what I was saying
is that timer may be running, and interrupted by a very long running
interrupt, say on CPU 0. Then, say, we unregister and free hsr_dev on 
CPU 1. When CPU 0 resumes running the timer code it will UAF on hsr_dev.
Again, probably completely theoretical.

> Anyway:
> 
> Acked-by: Lukasz Majewski <lukma@...x.de>

Thanks!