linux-kernel - Re: net/can: warning in bcm_connect/proc

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Message-ID: <CAM_iQpUAw6R1P-CQ-YJAYzb-HJXqUKAhJ5rLwp1L-ie3VkprSQ@mail.gmail.com>
Date:   Mon, 24 Oct 2016 09:58:54 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Andrey Konovalov <andreyknvl@...gle.com>
Cc:     Oliver Hartkopp <socketcan@...tkopp.net>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        "David S. Miller" <davem@...emloft.net>, linux-can@...r.kernel.org,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        syzkaller <syzkaller@...glegroups.com>,
        Kostya Serebryany <kcc@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: net/can: warning in bcm_connect/proc_register

On Mon, Oct 24, 2016 at 9:21 AM, Andrey Konovalov <andreyknvl@...gle.com> wrote:
> Hi,
>
> I've got the following error report while running the syzkaller fuzzer:
>
> WARNING: CPU: 0 PID: 32451 at fs/proc/generic.c:345 proc_register+0x25e/0x300
> proc_dir_entry 'can-bcm/249757' already registered
> Kernel panic - not syncing: panic_on_warn set ...

Looks like we have two problems here:

1) A check for bo->bcm_proc_read != NULL seems missing
2) We need to lock the sock in bcm_connect().

I will work on a patch. Meanwhile, it would help a lot if you could provide
a reproducer.

Thanks!