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Date: Mon, 2 Aug 2021 20:02:24 +0900 From: Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp> To: Hillf Danton <hdanton@...a.com>, Luiz Augusto von Dentz <luiz.dentz@...il.com> Cc: johan.hedberg@...il.com, linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org, luiz.von.dentz@...el.com, marcel@...tmann.org, netdev@...r.kernel.org, syzkaller-bugs@...glegroups.com, syzbot <syzbot+47c6d0efbb7fe2f7a5b8@...kaller.appspotmail.com> Subject: Re: [syzbot] general protection fault in hci_release_dev Hello. On 2021/08/02 18:54, Hillf Danton wrote: > To fix what was addressed in e305509e678b3a4a, defer putting hdev until > sock is released with sock locked. > > Now only for thoughts. Thanks for your analysis. hci_alloc_dev() is called from hci_uart_register_dev() from hci_uart_set_proto() from hci_uart_tty_ioctl(HCIUARTSETPROTO) via ld->ops->ioctl() from tty_ioctl(), and bt_host_release() is called from device_release() from kobject_put() from hci_uart_tty_close() from tty_ldisc_kill() from tty_ldisc_release() from tty_release_struct() from tty_release() from __fput(). The problem is that bt_host_release() is expecting that hci_register_dev() was called if "struct hci_dev" was allocated by hci_alloc_dev(). In other words, hci_register_dev() might not be called before bt_host_release(). Then, the fix I think is not to call hci_release_dev() when hci_unregister_dev() was not called. That is, static void bt_host_release(struct device *dev) { struct hci_dev *hdev = to_hci_dev(dev); + + if (hci_dev_test_flag(hdev, HCI_UNREGISTER)) + hci_release_dev(hdev); kfree(hdev); module_put(THIS_MODULE); } and remove kfree(hdev) from hci_release_dev(), for HCI_UNREGISTER flag is set if hci_unregister_dev() was called before bt_host_release() is called.
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