linux-kernel - Re: [BUG][RESEND] Bluetooth: L2CAP: possible data race in __sco_sock

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Date:   Mon, 1 May 2023 17:51:20 +0800
From:   Tuo Li <islituo@...il.com>
To:     Luiz Augusto von Dentz <luiz.dentz@...il.com>
Cc:     marcel@...tmann.org, johan.hedberg@...il.com,
        "David S. Miller" <davem@...emloft.net>, edumazet@...gle.com,
        Jakub Kicinski <kuba@...nel.org>, pabeni@...hat.com,
        linux-bluetooth@...r.kernel.org, netdev@...r.kernel.org,
        Linux Kernel <linux-kernel@...r.kernel.org>,
        baijiaju1990@...look.com
Subject: Re: [BUG][RESEND] Bluetooth: L2CAP: possible data race in
 __sco_sock_close()

Thanks for your reply and interests. Our static analysis tool is still 
to be improved, and any feedback on it would be appreciated.

On 2023/4/29 5:24, Luiz Augusto von Dentz wrote:
> Hi,
>
> On Fri, Apr 28, 2023 at 3:27 AM Li Tuo <islituo@...il.com> wrote:
>>    Hello,
>>
>> Our static analysis tool finds a possible data race in the l2cap protocol
>> in Linux 6.3.0-rc7:
>>
>> In most calling contexts, the variable sk->sk_socket is accessed
>> with holding the lock sk->sk_callback_lock. Here is an example:
>>
>>    l2cap_sock_accept() --> Line 346 in net/bluetooth/l2cap_sock.c
>>        bt_accept_dequeue() --> Line 368 in net/bluetooth/l2cap_sock.c
>>            sock_graft() --> Line 240 in net/bluetooth/af_bluetooth.c
>>                write_lock_bh(&sk->sk_callback_lock); --> Line 2081 in include/net/sock.h (Lock sk->sk_callback_lock)
>>                sk_set_socket() --> Line 2084 in include/net/sock.h
>>                    sk->sk_socket = sock; --> Line 2054 in include/net/sock.h (Access sk->sk_socket)
>>
>> However, in the following calling context:
>>
>>    sco_sock_shutdown() --> Line 1227 in net/bluetooth/sco.c
>>        __sco_sock_close() --> Line 1243 in net/bluetooth/sco.c
>>            BT_DBG(..., sk->sk_socket); --> Line 431 in net/bluetooth/sco.c (Access sk->sk_socket)
>>
>> the variable sk->sk_socket is accessed without holding the lock
>> sk->sk_callback_lock, and thus a data race may occur.
>>
>> Reported-by: BassCheck <bass@...a.edu.cn>
> Need to check in detail what it means to hold the sk_callback_lock,
> btw is this static analysis tool of yours something public that we can
> use in our CI to detect these problems?
>
>