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Subject: Re: [PATCH v2] Bluetooth: check for zapped sk before connecting
From:   Marcel Holtmann <marcel@holtmann.org>
In-Reply-To: <20210323163141.v2.1.I6c4306f6e8ba3ccc9106067d4eb70092f8cb2a49@changeid>
Date:   Tue, 23 Mar 2021 16:05:13 +0100
Cc:     linux-bluetooth <linux-bluetooth@vger.kernel.org>,
        CrosBT Upstreaming <chromeos-bluetooth-upstreaming@chromium.org>,
        Archie Pusaka <apusaka@chromium.org>,
        syzbot+abfc0f5e668d4099af73@syzkaller.appspotmail.com,
        Alain Michaud <alainm@chromium.org>,
        Abhishek Pandit-Subedi <abhishekpandit@chromium.org>,
        Guenter Roeck <groeck@chromium.org>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Johan Hedberg <johan.hedberg@gmail.com>,
        Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
        LKML <linux-kernel@vger.kernel.org>, netdev@vger.kernel.org
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Message-Id: <94F81995-4C43-4788-9EF1-54FB3C905784@holtmann.org>
References: <20210323163141.v2.1.I6c4306f6e8ba3ccc9106067d4eb70092f8cb2a49@changeid>
To:     Archie Pusaka <apusaka@google.com>
Precedence: bulk

Hi Archie,

> There is a possibility of receiving a zapped sock on
> l2cap_sock_connect(). This could lead to interesting crashes, one
> such case is tearing down an already tore l2cap_sock as is happened
> with this call trace:
> 
> __dump_stack lib/dump_stack.c:15 [inline]
> dump_stack+0xc4/0x118 lib/dump_stack.c:56
> register_lock_class kernel/locking/lockdep.c:792 [inline]
> register_lock_class+0x239/0x6f6 kernel/locking/lockdep.c:742
> __lock_acquire+0x209/0x1e27 kernel/locking/lockdep.c:3105
> lock_acquire+0x29c/0x2fb kernel/locking/lockdep.c:3599
> __raw_spin_lock_bh include/linux/spinlock_api_smp.h:137 [inline]
> _raw_spin_lock_bh+0x38/0x47 kernel/locking/spinlock.c:175
> spin_lock_bh include/linux/spinlock.h:307 [inline]
> lock_sock_nested+0x44/0xfa net/core/sock.c:2518
> l2cap_sock_teardown_cb+0x88/0x2fb net/bluetooth/l2cap_sock.c:1345
> l2cap_chan_del+0xa3/0x383 net/bluetooth/l2cap_core.c:598
> l2cap_chan_close+0x537/0x5dd net/bluetooth/l2cap_core.c:756
> l2cap_chan_timeout+0x104/0x17e net/bluetooth/l2cap_core.c:429
> process_one_work+0x7e3/0xcb0 kernel/workqueue.c:2064
> worker_thread+0x5a5/0x773 kernel/workqueue.c:2196
> kthread+0x291/0x2a6 kernel/kthread.c:211
> ret_from_fork+0x4e/0x80 arch/x86/entry/entry_64.S:604
> 
> Signed-off-by: Archie Pusaka <apusaka@chromium.org>
> Reported-by: syzbot+abfc0f5e668d4099af73@syzkaller.appspotmail.com
> Reviewed-by: Alain Michaud <alainm@chromium.org>
> Reviewed-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
> Reviewed-by: Guenter Roeck <groeck@chromium.org>
> ---
> 
> Changes in v2:
> * Modify locking order for better visibility
> 
> net/bluetooth/l2cap_sock.c | 8 ++++++++
> 1 file changed, 8 insertions(+)

patch has been applied to bluetooth-next tree.

Regards

Marcel