From patchwork Tue Jul 13 11:27:49 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tetsuo Handa X-Patchwork-Id: 12373783 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id ED953C07E95 for ; Tue, 13 Jul 2021 11:28:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C17B6611C0 for ; Tue, 13 Jul 2021 11:28:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235771AbhGMLbC (ORCPT ); Tue, 13 Jul 2021 07:31:02 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:56390 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235574AbhGMLbC (ORCPT ); Tue, 13 Jul 2021 07:31:02 -0400 Received: from fsav313.sakura.ne.jp (fsav313.sakura.ne.jp [153.120.85.144]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id 16DBRpRX036255; Tue, 13 Jul 2021 20:27:51 +0900 (JST) (envelope-from penguin-kernel@I-love.SAKURA.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav313.sakura.ne.jp (F-Secure/fsigk_smtp/550/fsav313.sakura.ne.jp); Tue, 13 Jul 2021 20:27:51 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/fsav313.sakura.ne.jp) Received: from [192.168.1.9] (M106072142033.v4.enabler.ne.jp [106.72.142.33]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id 16DBRp4q036252 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NO); Tue, 13 Jul 2021 20:27:51 +0900 (JST) (envelope-from penguin-kernel@I-love.SAKURA.ne.jp) Subject: [PATCH v3] Bluetooth: call lock_sock() outside of spinlock section From: Tetsuo Handa To: Marcel Holtmann , Johan Hedberg , Luiz Augusto von Dentz , linux-bluetooth@vger.kernel.org Cc: "David S. Miller" , Jakub Kicinski , Lin Ma , netdev@vger.kernel.org References: <20210627131134.5434-1-penguin-kernel@I-love.SAKURA.ne.jp> <9deece33-5d7f-9dcb-9aaa-94c60d28fc9a@i-love.sakura.ne.jp> Message-ID: <48d66166-4d39-4fe2-3392-7e0c84b9bdb3@i-love.sakura.ne.jp> Date: Tue, 13 Jul 2021 20:27:49 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <9deece33-5d7f-9dcb-9aaa-94c60d28fc9a@i-love.sakura.ne.jp> Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-bluetooth@vger.kernel.org syzbot is hitting might_sleep() warning at hci_sock_dev_event() due to calling lock_sock() with rw spinlock held [1]. Among three possible approaches [2], this patch chose holding a refcount via sock_hold() and revalidating the element via sk_hashed(). Link: https://syzkaller.appspot.com/bug?extid=a5df189917e79d5e59c9 [1] Link: https://lkml.kernel.org/r/05535d35-30d6-28b6-067e-272d01679d24@i-love.sakura.ne.jp [2] Reported-by: syzbot Signed-off-by: Tetsuo Handa Tested-by: syzbot Fixes: e305509e678b3a4a ("Bluetooth: use correct lock to prevent UAF of hdev object") --- Changes in v3: Don't use unlocked hci_pi(sk)->hdev != hdev test, for it is racy. No need to defer hci_dev_put(hdev), for it can't be the last reference. Changes in v2: Take hci_sk_list.lock for write in case bt_sock_unlink() is called after sk_hashed(sk) test, and defer hci_dev_put(hdev) till schedulable context. net/bluetooth/hci_sock.c | 30 +++++++++++++++++++++++++++++- 1 file changed, 29 insertions(+), 1 deletion(-) diff --git a/net/bluetooth/hci_sock.c b/net/bluetooth/hci_sock.c index b04a5a02ecf3..786a06a232fd 100644 --- a/net/bluetooth/hci_sock.c +++ b/net/bluetooth/hci_sock.c @@ -760,10 +760,18 @@ void hci_sock_dev_event(struct hci_dev *hdev, int event) struct sock *sk; /* Detach sockets from device */ +restart: read_lock(&hci_sk_list.lock); sk_for_each(sk, &hci_sk_list.head) { + /* This sock_hold(sk) is safe, for bt_sock_unlink(sk) + * is not called yet. + */ + sock_hold(sk); + read_unlock(&hci_sk_list.lock); lock_sock(sk); - if (hci_pi(sk)->hdev == hdev) { + write_lock(&hci_sk_list.lock); + /* Check that bt_sock_unlink(sk) is not called yet. */ + if (sk_hashed(sk) && hci_pi(sk)->hdev == hdev) { hci_pi(sk)->hdev = NULL; sk->sk_err = EPIPE; sk->sk_state = BT_OPEN; @@ -771,7 +779,27 @@ void hci_sock_dev_event(struct hci_dev *hdev, int event) hci_dev_put(hdev); } + write_unlock(&hci_sk_list.lock); release_sock(sk); + read_lock(&hci_sk_list.lock); + /* If bt_sock_unlink(sk) is not called yet, we can + * continue iteration. We can use __sock_put(sk) here + * because hci_sock_release() will call sock_put(sk) + * after bt_sock_unlink(sk). + */ + if (sk_hashed(sk)) { + __sock_put(sk); + continue; + } + /* Otherwise, we need to restart iteration, for the + * next socket pointed by sk->next might be already + * gone. We can't use __sock_put(sk) here because + * hci_sock_release() might have already called + * sock_put(sk) after bt_sock_unlink(sk). + */ + read_unlock(&hci_sk_list.lock); + sock_put(sk); + goto restart; } read_unlock(&hci_sk_list.lock); }