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From:   Sven Eckelmann <sven@narfation.org>
To:     syzbot <syzbot+28b0702ada0bf7381f58@syzkaller.appspotmail.com>,
        a@unstable.cc, b.a.t.m.a.n@lists.open-mesh.org,
        davem@davemloft.net, kuba@kernel.org, linux-kernel@vger.kernel.org,
        mareklindner@neomailbox.ch, netdev@vger.kernel.org,
        sw@simonwunderlich.de, syzkaller-bugs@googlegroups.com,
        Pavel Skripkin <paskripkin@gmail.com>, linus.luessing@c0d3.blue
Subject: Re: [syzbot] WARNING in batadv_nc_mesh_free
Date:   Sat, 23 Oct 2021 09:41:04 +0200
Message-ID: <2056331.oJahCzYEoq@sven-desktop>
In-Reply-To: <5e29e63c-d2b5-ae72-0e33-5a22e727be3c@gmail.com>
References: <000000000000c87fbd05cef6bcb0@google.com> <1639fcba-e543-e071-f17c-941b8c7a948f@gmail.com> <5e29e63c-d2b5-ae72-0e33-5a22e727be3c@gmail.com>
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From: Sven Eckelmann <sven@narfation.org>
To: syzbot <syzbot+28b0702ada0bf7381f58@syzkaller.appspotmail.com>, a@unstable.cc, b.a.t.m.a.n@lists.open-mesh.org, davem@davemloft.net, kuba@kernel.org, linux-kernel@vger.kernel.org, mareklindner@neomailbox.ch, netdev@vger.kernel.org, sw@simonwunderlich.de, syzkaller-bugs@googlegroups.com, Pavel Skripkin <paskripkin@gmail.com>, linus.luessing@c0d3.blue
Subject: Re: [syzbot] WARNING in batadv_nc_mesh_free
Date: Sat, 23 Oct 2021 09:41:04 +0200
Message-ID: <2056331.oJahCzYEoq@sven-desktop>
In-Reply-To: <5e29e63c-d2b5-ae72-0e33-5a22e727be3c@gmail.com>
References: <000000000000c87fbd05cef6bcb0@google.com> <1639fcba-e543-e071-f17c-941b8c7a948f@gmail.com> <5e29e63c-d2b5-ae72-0e33-5a22e727be3c@gmail.com>

On Friday, 22 October 2021 22:58:15 CEST Pavel Skripkin wrote:
[...]
> > Oh, ok. Next clean up call in batadv_nc_mesh_free() caused GPF, since
> > fields are not initialized. Let's try to clean up one by one and do not
> > break dependencies.
> > 
> > Quite ugly one, but idea is correct, I guess
> > 
> > Also, make each *_init() call clean up all allocated stuff to not call
> > corresponding *_free() on error handling path, since it introduces
> > problems, as syzbot reported

Thanks for the patch + syzbot interactions. I just wanted to implement a 
change - which would most likely have ended up the same way. Can you please 
send it to netdev and Cc b.a.t.m.a.n@lists.open-mesh.org? We don't have 
anything else to submit at the moment for netdev and this patch can be applied 
by netdev directly. I will add my Acked-by in this process.

Not sure about the Fixes. It is definitely wrong in the initial commit.... but 
it got only really problematic when other features got introduced. I would 
still say that the initial one should be mentioned.

Fixes: c6c8fea29769 ("net: Add batman-adv meshing protocol")

@Linus, @Marek, @Antonio: Please check whether it is ok to move the 
batadv_v_mesh_init after batadv_tt_init + batadv_originator_init. 
batadv_v_mesh_init is basically there to initialize:

* bat_priv->bat_v.ogm_buff(|_len|_mutex)
* bat_priv->bat_v.ogm_seqno
* bat_priv->bat_v.ogm_wq

batadv_originator_init is there to initialize the 

* bat_priv->orig_hash
* bat_priv->orig_work (batadv_purge_orig) + queue it up

batadv_tt_init is a lot more complex but should in theory not interact with 
ogm specific algo ops.

I wouldn't know why there could be a problem but I would leave it to the 
experts.

Kind regards,
	Sven
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