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

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Message-ID: <6a9b1524-9abe-fbfb-3335-a88ed297fdd1@uni-rostock.de>
Date:   Thu, 1 Mar 2018 18:48:38 +0100
From:   Benjamin Beichler <Benjamin.Beichler@...-rostock.de>
To:     Johannes Berg <johannes@...solutions.net>,
        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>
Subject: Re: KASAN: use-after-free Read in mac80211_hwsim_del_radio

Am 01.03.2018 um 10:30 schrieb Johannes Berg:
> 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
>
After having a look, we can not asynchronously delete the interfaces
here, because after the callback they need to be already gone. We could
simply put a workqueue flush after the loop, but since we have no
unbounded workqueue (which would also not be useful here I think), this
only will delay things further. Therefore I will create a patch, which
deletes synchronously here.

-- 
M.Sc. Benjamin Beichler

Universität Rostock, Fakultät für Informatik und Elektrotechnik
Institut für Angewandte Mikroelektronik und Datentechnik

University of Rostock, Department of CS and EE
Institute of Applied Microelectronics and CE

Richard-Wagner-Straße 31
18119 Rostock
Deutschland/Germany

phone: +49 (0) 381 498 - 7278
email: Benjamin.Beichler@...-rostock.de
www: http://www.imd.uni-rostock.de/



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