From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> To: Luiz Augusto von Dentz <luiz.dentz@gmail.com>, Lin Ma <linma@zju.edu.cn> Cc: Marcel Holtmann <marcel@holtmann.org>, Johan Hedberg <johan.hedberg@gmail.com>, "linux-bluetooth@vger.kernel.org" <linux-bluetooth@vger.kernel.org>, "David S. Miller" <davem@davemloft.net>, Jakub Kicinski <kuba@kernel.org>, "open list:NETWORKING [GENERAL]" <netdev@vger.kernel.org> Subject: Re: [PATCH v2] Bluetooth: call lock_sock() outside of spinlock section Date: Sat, 10 Jul 2021 22:34:29 +0900 [thread overview] Message-ID: <9771b40f-b544-a2a7-04e1-eddb38a4aae7@i-love.sakura.ne.jp> (raw) In-Reply-To: <79694c01-b69e-a039-6860-d7e612fbc008@i-love.sakura.ne.jp> On 2021/07/08 8:33, Tetsuo Handa wrote: >> we could perhaps don't release the reference to hdev >> either and leave hci_sock_release to deal with it and then perhaps we >> can take away the backward goto, actually why are you restarting to >> begin with? > > Do you mean something like > > diff --git a/net/bluetooth/hci_sock.c b/net/bluetooth/hci_sock.c > index b04a5a02ecf3..0525883f4639 100644 > --- a/net/bluetooth/hci_sock.c > +++ b/net/bluetooth/hci_sock.c > @@ -759,19 +759,14 @@ void hci_sock_dev_event(struct hci_dev *hdev, int event) > if (event == HCI_DEV_UNREG) { > struct sock *sk; > > - /* Detach sockets from device */ > + /* Change socket state and notify */ > read_lock(&hci_sk_list.lock); > sk_for_each(sk, &hci_sk_list.head) { > - lock_sock(sk); > if (hci_pi(sk)->hdev == hdev) { > - hci_pi(sk)->hdev = NULL; > sk->sk_err = EPIPE; > sk->sk_state = BT_OPEN; > sk->sk_state_change(sk); > - > - hci_dev_put(hdev); > } > - release_sock(sk); > } > read_unlock(&hci_sk_list.lock); > } > > ? I can't judge because I don't know how this works. I worry that > without lock_sock()/release_sock(), this races with e.g. hci_sock_bind(). > I examined hci_unregister_dev() and concluded that this can't work. hci_sock_dev_event(hdev, HCI_DEV_UNREG) can't defer dropping the reference to this hdev till hci_sock_release(), for hci_unregister_dev() cleans up everything related to this hdev and calls hci_dev_put(hdev) and then vhci_release() calls hci_free_dev(hdev). That's the reason hci_sock_dev_event() has to use lock_sock() in order not to miss some hci_dev_put(hdev) calls. >> This sounds a little too complicated, afaik backward goto is not even >> consider a good practice either, since it appears we don't unlink the >> sockets here Despite your comment, I'd like to go with choice (3) for now. After lock_sock() became free from delay caused by pagefault handling, we could consider updating to choice (1).
next prev parent reply other threads:[~2021-07-10 13:34 UTC|newest] Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-06-27 13:11 [PATCH] " Tetsuo Handa 2021-06-27 14:05 ` bluez.test.bot 2021-07-07 9:43 ` [PATCH v2] " Tetsuo Handa 2021-07-07 10:08 ` [v2] " bluez.test.bot 2021-07-07 18:20 ` [PATCH v2] " Luiz Augusto von Dentz 2021-07-07 23:33 ` Tetsuo Handa 2021-07-08 1:00 ` LinMa 2021-07-09 13:50 ` Tetsuo Handa 2021-07-10 13:34 ` Tetsuo Handa [this message] 2021-07-08 7:16 ` [v2] " bluez.test.bot 2021-07-13 11:27 ` [PATCH v3] " Tetsuo Handa 2021-07-13 11:57 ` [v3] " bluez.test.bot 2021-07-14 19:20 ` [PATCH v3] " Luiz Augusto von Dentz 2021-07-15 3:03 ` LinMa 2021-07-16 3:47 ` Desmond Cheong Zhi Xi 2021-07-16 4:11 ` Desmond Cheong Zhi Xi 2021-07-16 14:48 ` Tetsuo Handa 2021-07-16 15:26 ` LinMa 2021-07-17 15:41 ` Yet Another Patch for CVE-2021-3573 LinMa 2021-07-17 15:45 ` LinMa 2021-07-22 9:36 ` [PATCH v3] Bluetooth: call lock_sock() outside of spinlock section Tetsuo Handa 2021-07-22 4:47 ` LinMa 2021-07-22 5:16 ` Tetsuo Handa
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