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=-6.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,T_DKIMWL_WL_HIGH,USER_AGENT_GIT autolearn=unavailable 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 0A457C28EBD for ; Sun, 9 Jun 2019 17:15:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D46EF20652 for ; Sun, 9 Jun 2019 17:15:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1560100518; bh=GxAF82jmbHUaL0yfFm5AxkUdu9m3RmmEnyD+8b2kNlg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=JX0cbDKvjb+tTMm6rApJlsuxeHZTgsZ1I4MEGEPLc7RcdLpdKa7zDRrCkP44lran4 0FTNqYHkwcgQHrf1yU6qdWUt0iEXGwFi2IX7c9JlkOlWSk9UpH8PlvvYpVCN1SG3Qn 3iYicHwd/EZcFdFBXC7gvbeeyq39wZKT1FxsJCCo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732005AbfFIQzC (ORCPT ); Sun, 9 Jun 2019 12:55:02 -0400 Received: from mail.kernel.org ([198.145.29.99]:57012 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732313AbfFIQzB (ORCPT ); Sun, 9 Jun 2019 12:55:01 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 7AE7D206C3; Sun, 9 Jun 2019 16:55:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1560099301; bh=GxAF82jmbHUaL0yfFm5AxkUdu9m3RmmEnyD+8b2kNlg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=b62i6yfyYmEhJKUR2pRDKoJk5hE9ovxPCfxrBoDZL5tRx0ag0dgYOpLUaBowbSHPV Lkc7rp2IFmO4J5cPuc8QryOLnE60kvJG7O2E3BsnvNPdEgj60o7/KxV5LqjXkXsCZc hjRmXlHxlkmYxfelMvMIAB0YMChOE7MDTZ5XARAc= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jiri Slaby , Li RongQing , Wang Li , Zhang Yu Subject: [PATCH 4.9 81/83] TTY: serial_core, add ->install Date: Sun, 9 Jun 2019 18:42:51 +0200 Message-Id: <20190609164134.856500825@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190609164127.843327870@linuxfoundation.org> References: <20190609164127.843327870@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Jiri Slaby commit 4cdd17ba1dff20ffc99fdbd2e6f0201fc7fe67df upstream. We need to compute the uart state only on the first open. This is usually what is done in the ->install hook. serial_core used to do this in ->open on every open. So move it to ->install. As a side effect, it ensures the state is set properly in the window after tty_init_dev is called, but before uart_open. This fixes a bunch of races between tty_open and flush_to_ldisc we were dealing with recently. One of such bugs was attempted to fix in commit fedb5760648a (serial: fix race between flush_to_ldisc and tty_open), but it only took care of a couple of functions (uart_start and uart_unthrottle). I was able to reproduce the crash on a SLE system, but in uart_write_room which is also called from flush_to_ldisc via process_echoes. I was *unable* to reproduce the bug locally. It is due to having this patch in my queue since 2012! general protection fault: 0000 [#1] SMP KASAN PTI CPU: 1 PID: 5 Comm: kworker/u4:0 Tainted: G L 4.12.14-396-default #1 SLE15-SP1 (unreleased) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-0-ga698c89-prebuilt.qemu.org 04/01/2014 Workqueue: events_unbound flush_to_ldisc task: ffff8800427d8040 task.stack: ffff8800427f0000 RIP: 0010:uart_write_room+0xc4/0x590 RSP: 0018:ffff8800427f7088 EFLAGS: 00010202 RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 000000000000002f RSI: 00000000000000ee RDI: ffff88003888bd90 RBP: ffffffffb9545850 R08: 0000000000000001 R09: 0000000000000400 R10: ffff8800427d825c R11: 000000000000006e R12: 1ffff100084fee12 R13: ffffc900004c5000 R14: ffff88003888bb28 R15: 0000000000000178 FS: 0000000000000000(0000) GS:ffff880043300000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000561da0794148 CR3: 000000000ebf4000 CR4: 00000000000006e0 Call Trace: tty_write_room+0x6d/0xc0 __process_echoes+0x55/0x870 n_tty_receive_buf_common+0x105e/0x26d0 tty_ldisc_receive_buf+0xb7/0x1c0 tty_port_default_receive_buf+0x107/0x180 flush_to_ldisc+0x35d/0x5c0 ... 0 in rbx means tty->driver_data is NULL in uart_write_room. 0x178 is tried to be dereferenced (0x178 >> 3 is 0x2f in rdx) at uart_write_room+0xc4. 0x178 is exactly (struct uart_state *)NULL->refcount used in uart_port_lock from uart_write_room. So revert the upstream commit here as my local patch should fix the whole family. Signed-off-by: Jiri Slaby Cc: Li RongQing Cc: Wang Li Cc: Zhang Yu Cc: Greg Kroah-Hartman Cc: stable Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/serial_core.c | 24 +++++++++++++----------- 1 file changed, 13 insertions(+), 11 deletions(-) --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -141,9 +141,6 @@ static void uart_start(struct tty_struct struct uart_port *port; unsigned long flags; - if (!state) - return; - port = uart_port_lock(state, flags); __uart_start(tty); uart_port_unlock(port, flags); @@ -1714,11 +1711,8 @@ static void uart_dtr_rts(struct tty_port */ static int uart_open(struct tty_struct *tty, struct file *filp) { - struct uart_driver *drv = tty->driver->driver_state; - int retval, line = tty->index; - struct uart_state *state = drv->state + line; - - tty->driver_data = state; + struct uart_state *state = tty->driver_data; + int retval; retval = tty_port_open(&state->port, tty, filp); if (retval > 0) @@ -2409,9 +2403,6 @@ static void uart_poll_put_char(struct tt struct uart_state *state = drv->state + line; struct uart_port *port; - if (!state) - return; - port = uart_port_ref(state); if (!port) return; @@ -2423,7 +2414,18 @@ static void uart_poll_put_char(struct tt } #endif +static int uart_install(struct tty_driver *driver, struct tty_struct *tty) +{ + struct uart_driver *drv = driver->driver_state; + struct uart_state *state = drv->state + tty->index; + + tty->driver_data = state; + + return tty_standard_install(driver, tty); +} + static const struct tty_operations uart_ops = { + .install = uart_install, .open = uart_open, .close = uart_close, .write = uart_write,