netdev - Re: KASAN: use-after-free Read in mac80211_hwsim_del

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Message-ID: <1519896638.2292.7.camel@sipsolutions.net>
Date:   Thu, 01 Mar 2018 10:30:38 +0100
From:   Johannes Berg <johannes@...solutions.net>
To:     syzbot <syzbot+70ce058e01259de7bb1d@...kaller.appspotmail.com>,
        kvalo@...eaurora.org, linux-kernel@...r.kernel.org,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        syzkaller-bugs@...glegroups.com,
        Benjamin Beichler <benjamin.beichler@...-rostock.de>
Subject: Re: KASAN: use-after-free Read in mac80211_hwsim_del_radio

Hi,

> syzbot hit the following crash on upstream commit
> f3afe530d644488a074291da04a69a296ab63046 (Tue Feb 27 22:02:39 2018 +0000)
> Merge branch 'fixes-v4.16-rc4' of  
> git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security
> 
> So far this crash happened 4 times on upstream.
> Unfortunately, I don't have any reproducer for this crash yet.
> Raw console output is attached.

That's ... a pretty complex scenario.

Looks like we have a race between destroying a network namespace, which
moves everything back into the init_ns and may have to rename objects
asynchronously (cleanup_net), with destroying the radio in hwsim that's
also asynchronous (destroy_radio).

Benjamin, would you be able to take a look at this? I'm preparing for a
trip and will leave Saturday for a week so I don't think I'll be able
to really dig into this before mid-March.

johannes