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From:   Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Date:   Fri, 28 Apr 2023 14:24:40 -0700
Message-ID: <CABBYNZJCbYnxodwXAeq8F9NerzGWFva0OG6SfUWfJ_Grz=Xq6Q@mail.gmail.com>
Subject: Re: [BUG][RESEND] Bluetooth: L2CAP: possible data race in __sco_sock_close()
To:     Li Tuo <islituo@gmail.com>
Cc:     marcel@holtmann.org, johan.hedberg@gmail.com,
        "David S. Miller" <davem@davemloft.net>, edumazet@google.com,
        Jakub Kicinski <kuba@kernel.org>, pabeni@redhat.com,
        linux-bluetooth@vger.kernel.org, netdev@vger.kernel.org,
        Linux Kernel <linux-kernel@vger.kernel.org>,
        baijiaju1990@outlook.com
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Hi,

On Fri, Apr 28, 2023 at 3:27=E2=80=AFAM Li Tuo <islituo@gmail.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 incl=
ude/net/sock.h (Lock sk->sk_callback_lock)
>               sk_set_socket() --> Line 2084 in include/net/sock.h
>                   sk->sk_socket =3D sock; --> Line 2054 in include/net/so=
ck.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@buaa.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?


--=20
Luiz Augusto von Dentz