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From:   Sven Eckelmann <sven@narfation.org>
To:     Marek Lindner <mareklindner@neomailbox.ch>,
        Vladislav Efanov <VEfanov@ispras.ru>
Cc:     Simon Wunderlich <sw@simonwunderlich.de>,
        Antonio Quartulli <a@unstable.cc>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        b.a.t.m.a.n@lists.open-mesh.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, lvc-project@linuxtesting.org
Subject: Re: [PATCH] batman-adv: Broken sync while rescheduling delayed work
Date:   Fri, 26 May 2023 22:30:16 +0200
Message-ID: <7526514.EvYhyI6sBW@sven-l14>
In-Reply-To: <20230526161632.1460753-1-VEfanov@ispras.ru>
References: <20230526161632.1460753-1-VEfanov@ispras.ru>
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From: Sven Eckelmann <sven@narfation.org>
Date: Fri, 26 May 2023 22:30:16 +0200
Message-ID: <7526514.EvYhyI6sBW@sven-l14>
In-Reply-To: <20230526161632.1460753-1-VEfanov@ispras.ru>
References: <20230526161632.1460753-1-VEfanov@ispras.ru>
MIME-Version: 1.0

On Friday, 26 May 2023 18:16:32 CEST Vladislav Efanov wrote:
> Syzkaller got a lot of crashes like:
> KASAN: use-after-free Write in *_timers*
> 
> All of these crashes point to the same memory area:
> 
> The buggy address belongs to the object at ffff88801f870000
>  which belongs to the cache kmalloc-8k of size 8192
> The buggy address is located 5320 bytes inside of
>  8192-byte region [ffff88801f870000, ffff88801f872000)
> 
> This area belongs to :
>         batadv_priv->batadv_priv_dat->delayed_work->timer_list
> 
> The reason for these issues is the lack of synchronization. Delayed
> work (batadv_dat_purge) schedules new timer/work while the device
> is being deleted. As the result new timer/delayed work is set after
> cancel_delayed_work_sync() was called. So after the device is freed
> the timer list contains pointer to already freed memory.
> 
> Found by Linux Verification Center (linuxtesting.org) with syzkaller.
> 
> Fixes: 2f1dfbe18507 ("batman-adv: Distributed ARP Table - implement local storage")
> Signed-off-by: Vladislav Efanov <VEfanov@ispras.ru>
> ---


Acked-by: Sven Eckelmann <sven@narfation.org>

Thanks,
	Sven
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