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=-20.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, 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 464ADC433FE for ; Mon, 20 Sep 2021 17:18:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2E37F6325C for ; Mon, 20 Sep 2021 17:18:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346845AbhITRUL (ORCPT ); Mon, 20 Sep 2021 13:20:11 -0400 Received: from mail.kernel.org ([198.145.29.99]:45924 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346683AbhITRSd (ORCPT ); Mon, 20 Sep 2021 13:18:33 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id B581D613D2; Mon, 20 Sep 2021 16:59:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1632157183; bh=+u2gdY82twVzZc/+FP/9XeCbDZTaNroa7jCYQ0Oh/lM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=sJ0U11GO7XPTcyYPUG1n453ML23Lv/KrZ1LmDP/2DHp72sexpeRoU8W2OWqEOyXc1 DQNK3lL0Y8eh5KeKUIFzs9kTV1m8kslPRmzaGJ3VRnD1/8Xp1nNvZWK1q1pDlWfII+ hGHRaAwvZoOmDCd0zrdUDjUeGiF/m+V8ih+TEqHw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot+97388eb9d31b997fe1d0@syzkaller.appspotmail.com, Jiri Slaby , Nguyen Dinh Phi Subject: [PATCH 4.14 091/217] tty: Fix data race between tiocsti() and flush_to_ldisc() Date: Mon, 20 Sep 2021 18:41:52 +0200 Message-Id: <20210920163927.721004034@linuxfoundation.org> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20210920163924.591371269@linuxfoundation.org> References: <20210920163924.591371269@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Nguyen Dinh Phi commit bb2853a6a421a052268eee00fd5d3f6b3504b2b1 upstream. The ops->receive_buf() may be accessed concurrently from these two functions. If the driver flushes data to the line discipline receive_buf() method while tiocsti() is waiting for the ops->receive_buf() to finish its work, the data race will happen. For example: tty_ioctl |tty_ldisc_receive_buf ->tioctsi | ->tty_port_default_receive_buf | ->tty_ldisc_receive_buf ->hci_uart_tty_receive | ->hci_uart_tty_receive ->h4_recv | ->h4_recv In this case, the h4 receive buffer will be overwritten by the latecomer, and we will lost the data. Hence, change tioctsi() function to use the exclusive lock interface from tty_buffer to avoid the data race. Reported-by: syzbot+97388eb9d31b997fe1d0@syzkaller.appspotmail.com Reviewed-by: Jiri Slaby Signed-off-by: Nguyen Dinh Phi Link: https://lore.kernel.org/r/20210823000641.2082292-1-phind.uet@gmail.com Cc: stable Signed-off-by: Greg Kroah-Hartman --- drivers/tty/tty_io.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -2165,8 +2165,6 @@ static int tty_fasync(int fd, struct fil * Locking: * Called functions take tty_ldiscs_lock * current->signal->tty check is safe without locks - * - * FIXME: may race normal receive processing */ static int tiocsti(struct tty_struct *tty, char __user *p) @@ -2182,8 +2180,10 @@ static int tiocsti(struct tty_struct *tt ld = tty_ldisc_ref_wait(tty); if (!ld) return -EIO; + tty_buffer_lock_exclusive(tty->port); if (ld->ops->receive_buf) ld->ops->receive_buf(tty, &ch, &mbz, 1); + tty_buffer_unlock_exclusive(tty->port); tty_ldisc_deref(ld); return 0; }