From mboxrd@z Thu Jan 1 00:00:00 1970 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=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 9C19EC433E0 for ; Fri, 5 Feb 2021 14:00:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4EB9164FC6 for ; Fri, 5 Feb 2021 14:00:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231708AbhBEOAA (ORCPT ); Fri, 5 Feb 2021 09:00:00 -0500 Received: from www262.sakura.ne.jp ([202.181.97.72]:64979 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229752AbhBEN6M (ORCPT ); Fri, 5 Feb 2021 08:58:12 -0500 Received: from fsav302.sakura.ne.jp (fsav302.sakura.ne.jp [153.120.85.133]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id 115Dv9b4037786; Fri, 5 Feb 2021 22:57:09 +0900 (JST) (envelope-from penguin-kernel@I-love.SAKURA.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav302.sakura.ne.jp (F-Secure/fsigk_smtp/550/fsav302.sakura.ne.jp); Fri, 05 Feb 2021 22:57:09 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/fsav302.sakura.ne.jp) Received: from localhost.localdomain (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 115Dv4gV037676 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Fri, 5 Feb 2021 22:57:09 +0900 (JST) (envelope-from penguin-kernel@I-love.SAKURA.ne.jp) From: Tetsuo Handa To: Greg Kroah-Hartman , Valentina Manea , Shuah Khan Cc: Shuah Khan , Hillf Danton , linux-usb@vger.kernel.org, Tetsuo Handa , Arnd Bergmann Subject: [PATCH] usb: usbip: fix error handling of kthread_get_run() Date: Fri, 5 Feb 2021 22:57:06 +0900 Message-Id: <20210205135707.4574-1-penguin-kernel@I-love.SAKURA.ne.jp> X-Mailer: git-send-email 2.18.4 In-Reply-To: <000000000000414db905b6e9bae8@google.com> References: <000000000000414db905b6e9bae8@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org syzbot is reporting a crash at vhci_shutdown_connection() [1]. It turned out that it was not a NULL pointer dereference but an ERR_PTR(-EINTR) pointer dereference, for kthread_create() became killable due to commit 786235eeba0e1e85 ("kthread: make kthread_create() killable"). When SIGKILLed while attach_store() is calling kthread_get_run(), ERR_PTR(-EINTR) is stored into vdev->ud.tcp_{rx,tx}, and then kthread_stop_put() is called on vdev->ud.tcp_{rx,tx} from vhci_shutdown_connection() because vdev->ud.tcp_{rx,tx} != NULL. Prior to commit 9720b4bc76a83807 ("staging/usbip: convert to kthread"), "current" pointer is assigned to vdev->ud.tcp_{rx,tx} by usbip_thread() kernel thread, and hence vdev->ud.tcp_{rx,tx} != NULL meant a valid task pointer. Therefore, we should make kthread_get_run() return NULL when kthread_create() failed. [1] https://syzkaller.appspot.com/bug?id=c21c07f3d51769405e8efc027bdb927515dcc7d6 Reported-by: syzbot Reported-by: syzbot Signed-off-by: Tetsuo Handa Fixes: 9720b4bc76a83807 ("staging/usbip: convert to kthread") Cc: Arnd Bergmann --- drivers/usb/usbip/usbip_common.h | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/usb/usbip/usbip_common.h b/drivers/usb/usbip/usbip_common.h index 8be857a4fa13..a7c68097aa1d 100644 --- a/drivers/usb/usbip/usbip_common.h +++ b/drivers/usb/usbip/usbip_common.h @@ -286,6 +286,8 @@ struct usbip_device { if (!IS_ERR(__k)) { \ get_task_struct(__k); \ wake_up_process(__k); \ + } else { \ + __k = NULL; \ } \ __k; \ }) -- 2.18.4