From patchwork Tue Jan 4 16:35:45 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Arnaud POULIQUEN X-Patchwork-Id: 12703638 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0083BC433EF for ; Tue, 4 Jan 2022 16:36:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235363AbiADQgA (ORCPT ); Tue, 4 Jan 2022 11:36:00 -0500 Received: from mx08-00178001.pphosted.com ([91.207.212.93]:60808 "EHLO mx07-00178001.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S235367AbiADQf7 (ORCPT ); Tue, 4 Jan 2022 11:35:59 -0500 Received: from pps.filterd (m0046661.ppops.net [127.0.0.1]) by mx07-00178001.pphosted.com (8.16.1.2/8.16.1.2) with ESMTP id 204FLlE9029256; Tue, 4 Jan 2022 17:35:51 +0100 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=foss.st.com; h=from : to : cc : subject : date : message-id : mime-version : content-transfer-encoding : content-type; s=selector1; bh=+jWUHPERe/nevyKX3aqinPpPiMKKYwzJ7ruEcy/S6Pg=; b=PnbqfR3AHdZfDPPtgTZR3iBZIvYHE1obPniwFMAXOENKMnG1UFd2D5A04Fci427gvcYn 1ZEZbe8OAECSecxdP64WLTgNBTy8IbCaU5OaT63dxcUsplu1WZQSClb5nCi89PsQ/I67 CyAsFaOpXsiBZrXJwMBQNDMr9xKaGWs0MFME1PanCbOPp3ck4AfFMgXKeHES4GbwHYXn ux9tVwJQ76rVKVr4FJhJV/KUStH80IVIEtVAAyX1Rgu7o4/iWy+sv7ei+2nkYAfVor27 p22Saf35leC0h5ow0p+x4koBG8kX06kqOWbslMq5lLV6bpDnoj8t9eSPsTGRY9yc3WVx oA== Received: from beta.dmz-eu.st.com (beta.dmz-eu.st.com [164.129.1.35]) by mx07-00178001.pphosted.com (PPS) with ESMTPS id 3dcagrbv9p-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 04 Jan 2022 17:35:51 +0100 Received: from euls16034.sgp.st.com (euls16034.sgp.st.com [10.75.44.20]) by beta.dmz-eu.st.com (STMicroelectronics) with ESMTP id 4DFA610002A; Tue, 4 Jan 2022 17:35:50 +0100 (CET) Received: from Webmail-eu.st.com (sfhdag2node2.st.com [10.75.127.5]) by euls16034.sgp.st.com (STMicroelectronics) with ESMTP id 30692245CC5; Tue, 4 Jan 2022 17:35:50 +0100 (CET) Received: from localhost (10.75.127.49) by SFHDAG2NODE2.st.com (10.75.127.5) with Microsoft SMTP Server (TLS) id 15.0.1497.26; Tue, 4 Jan 2022 17:35:49 +0100 From: Arnaud Pouliquen To: Greg Kroah-Hartman , Jiri Slaby CC: Bjorn Andersson , Mathieu Poirier , , , , Subject: [PATCH v4] tty: rpmsg: Fix race condition releasing tty port Date: Tue, 4 Jan 2022 17:35:45 +0100 Message-ID: <20220104163545.34710-1-arnaud.pouliquen@foss.st.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 X-Originating-IP: [10.75.127.49] X-ClientProxiedBy: SFHDAG2NODE1.st.com (10.75.127.4) To SFHDAG2NODE2.st.com (10.75.127.5) X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.790,Hydra:6.0.425,FMLib:17.11.62.513 definitions=2022-01-04_07,2022-01-04_01,2021-12-02_01 Precedence: bulk List-ID: X-Mailing-List: linux-remoteproc@vger.kernel.org The tty_port struct is part of the rpmsg_tty_port structure. The issue is that the rpmsg_tty_port structure is freed on rpmsg_tty_remove while it is still referenced in the tty_struct. Its release is not predictable due to workqueues. For instance following ftrace shows that rpmsg_tty_close is called after rpmsg_tty_release_cport: nr_test.sh-389 [000] ..... 212.093752: rpmsg_tty_remove <-rpmsg_dev_ remove cat-1191 [001] ..... 212.095697: tty_release <-__fput nr_test.sh-389 [000] ..... 212.099166: rpmsg_tty_release_cport <-rpm sg_tty_remove cat-1191 [001] ..... 212.115352: rpmsg_tty_close <-tty_release cat-1191 [001] ..... 212.115371: release_tty <-tty_release_str As consequence, the port must be free only when user has released the TTY interface. This path : - Introduce the .destruct port tty ops function to release the allocated rpmsg_tty_port structure. - Introduce the .hangup tty ops function to call tty_port_hangup. - Manages the tty port refcounting to trig the .destruct port ops, - Introduces the rpmsg_tty_cleanup function to ensure that the TTY is removed before decreasing the port refcount. Fixes: 7c0408d80579 ("tty: add rpmsg driver") Signed-off-by: Arnaud Pouliquen --- delta vs V3 [1]: take into account Greg Kroah-Hartman's comments: - remove uses of tty_vhangup instead of tty_port_tty_hangup. - remove useless WARM_ON(!cport) in rpmsg_tty_cleanup. Remaining point to clarify: Is it a benefict to use tty_vhangup as done in V3 [1] instead of tty_hangup (called by tty_port_tty_hangup)? In both cases, tty_kref_put calls queue_release_one_tty making the rest of the release asynchronous. -> proposal to address this in a separate patchset if needed (introducing tty_port_tty_vhangup helper). [1]https://lore.kernel.org/all/YcGN0fDn2hqAdrP9@kroah.com/T/#m4e02ed9ca71387f447b5dc35402f10f4313f44d2 of Applied and tested on fa55b7dcdc43 ("Linux 5.16-rc1", 2021-11-14) --- drivers/tty/rpmsg_tty.c | 40 ++++++++++++++++++++++++++-------------- 1 file changed, 26 insertions(+), 14 deletions(-) diff --git a/drivers/tty/rpmsg_tty.c b/drivers/tty/rpmsg_tty.c index dae2a4e44f38..29db413bbc03 100644 --- a/drivers/tty/rpmsg_tty.c +++ b/drivers/tty/rpmsg_tty.c @@ -50,10 +50,17 @@ static int rpmsg_tty_cb(struct rpmsg_device *rpdev, void *data, int len, void *p static int rpmsg_tty_install(struct tty_driver *driver, struct tty_struct *tty) { struct rpmsg_tty_port *cport = idr_find(&tty_idr, tty->index); + struct tty_port *port; tty->driver_data = cport; - return tty_port_install(&cport->port, driver, tty); + port = tty_port_get(&cport->port); + return tty_port_install(port, driver, tty); +} + +static void rpmsg_tty_cleanup(struct tty_struct *tty) +{ + tty_port_put(tty->port); } static int rpmsg_tty_open(struct tty_struct *tty, struct file *filp) @@ -106,12 +113,19 @@ static unsigned int rpmsg_tty_write_room(struct tty_struct *tty) return size; } +static void rpmsg_tty_hangup(struct tty_struct *tty) +{ + tty_port_hangup(tty->port); +} + static const struct tty_operations rpmsg_tty_ops = { .install = rpmsg_tty_install, .open = rpmsg_tty_open, .close = rpmsg_tty_close, .write = rpmsg_tty_write, .write_room = rpmsg_tty_write_room, + .hangup = rpmsg_tty_hangup, + .cleanup = rpmsg_tty_cleanup, }; static struct rpmsg_tty_port *rpmsg_tty_alloc_cport(void) @@ -137,8 +151,10 @@ static struct rpmsg_tty_port *rpmsg_tty_alloc_cport(void) return cport; } -static void rpmsg_tty_release_cport(struct rpmsg_tty_port *cport) +static void rpmsg_tty_destruct_port(struct tty_port *port) { + struct rpmsg_tty_port *cport = container_of(port, struct rpmsg_tty_port, port); + mutex_lock(&idr_lock); idr_remove(&tty_idr, cport->id); mutex_unlock(&idr_lock); @@ -146,7 +162,10 @@ static void rpmsg_tty_release_cport(struct rpmsg_tty_port *cport) kfree(cport); } -static const struct tty_port_operations rpmsg_tty_port_ops = { }; +static const struct tty_port_operations rpmsg_tty_port_ops = { + .destruct = rpmsg_tty_destruct_port, +}; + static int rpmsg_tty_probe(struct rpmsg_device *rpdev) { @@ -166,7 +185,8 @@ static int rpmsg_tty_probe(struct rpmsg_device *rpdev) cport->id, dev); if (IS_ERR(tty_dev)) { ret = dev_err_probe(dev, PTR_ERR(tty_dev), "Failed to register tty port\n"); - goto err_destroy; + tty_port_put(&cport->port); + return ret; } cport->rpdev = rpdev; @@ -177,12 +197,6 @@ static int rpmsg_tty_probe(struct rpmsg_device *rpdev) rpdev->src, rpdev->dst, cport->id); return 0; - -err_destroy: - tty_port_destroy(&cport->port); - rpmsg_tty_release_cport(cport); - - return ret; } static void rpmsg_tty_remove(struct rpmsg_device *rpdev) @@ -192,13 +206,11 @@ static void rpmsg_tty_remove(struct rpmsg_device *rpdev) dev_dbg(&rpdev->dev, "Removing rpmsg tty device %d\n", cport->id); /* User hang up to release the tty */ - if (tty_port_initialized(&cport->port)) - tty_port_tty_hangup(&cport->port, false); + tty_port_tty_hangup(&cport->port, false); tty_unregister_device(rpmsg_tty_driver, cport->id); - tty_port_destroy(&cport->port); - rpmsg_tty_release_cport(cport); + tty_port_put(&cport->port); } static struct rpmsg_device_id rpmsg_driver_tty_id_table[] = {