From patchwork Mon Jan 16 14:41:49 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Bartosz Golaszewski X-Patchwork-Id: 643643 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 8B135C63797 for ; Mon, 16 Jan 2023 14:54:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231199AbjAPOyN (ORCPT ); Mon, 16 Jan 2023 09:54:13 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44488 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232789AbjAPOxo (ORCPT ); Mon, 16 Jan 2023 09:53:44 -0500 Received: from mail-wr1-x42a.google.com (mail-wr1-x42a.google.com [IPv6:2a00:1450:4864:20::42a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8B71F23D9D for ; Mon, 16 Jan 2023 06:42:00 -0800 (PST) Received: by mail-wr1-x42a.google.com with SMTP id r9so4898818wrw.4 for ; Mon, 16 Jan 2023 06:42:00 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bgdev-pl.20210112.gappssmtp.com; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=0Ppko8Fem+qtirmYhp62EkgUMyaloOxSAW2RcoWpD8I=; b=8EI8vtH1yUk28VFMj92vw5wTOII6JxqTmxqBGNvfxrRf9qrzwu1wy4qOATNSQxjc9d R1UJ4qU2vEgWUuxmWQiWGyklnOrH5wV2LU+Ccv2embbP0WIETuvDcaXddLvjwyQRHD66 dbk5W9yLzTVC7r9xQ6kMStfb4kPSUEcfl+8j28OSk0lopTRCTRddJxa6EYyvsOuwUB3+ smD2q6ZAr6K+69W4Rv0jgvS8LM2gawH1uQamqOU0urnmv8/pZOTvCN7qxY7KuL1smhlz bvL86lYGRzOFWlBB/pCJmRn6AiWnFm7YM5i/CBulRWnbqgGVaA+PY4tEOUd3FExj9W7v vsXw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=0Ppko8Fem+qtirmYhp62EkgUMyaloOxSAW2RcoWpD8I=; b=CBqq2BgHbo8jH3h40UKGaGU0qQPGZllFeVgTzZMmdXhDtifiCoajKFxcJRnSA/NoXb thQnxVCSQte4zhbIRtel4+WYMylIVAN30kcQM+kqWy3++F2mapfUVPhVobGTVJfOSxQU afvLDXxcsxNj5R9mAoRD/xFand035AkD1feFjo3RmeiUmMWNnuu/TFvpBnvSQ3uXON15 nzCZ1gezYVEsp7Ursoxtk+iyOPOl1Gm/D3X32s3QMBeOTemaOZo0qFBdfhigVAaQ0ZzK /C2LzPWGh7scuq5H/JdHvensaCQd5xUauZ2kpnCtRvlBB0fU1xwpAwmL6EsgQGzl2XoQ h63Q== X-Gm-Message-State: AFqh2krTZlmhLbM1NndG9WAyZyMXy5cnCsR07amWrM7/aAnWeb9Za8i/ ZQGNjDS5tDpbG8vhGhzsRXhJnB8CPipgRwsX X-Google-Smtp-Source: AMrXdXvswhBZBHL3czGygVmuEp4kCJ4skGF7OFh/1qMOaUgNh5rRMgW34Z1OPN5a1reY/5IDqOTxPA== X-Received: by 2002:a5d:528e:0:b0:2bd:e99a:a8a9 with SMTP id c14-20020a5d528e000000b002bde99aa8a9mr7603936wrv.71.1673880119021; Mon, 16 Jan 2023 06:41:59 -0800 (PST) Received: from brgl-uxlite.home ([2a01:cb1d:334:ac00:2f9d:c271:2ba9:4f2a]) by smtp.gmail.com with ESMTPSA id r10-20020adfda4a000000b0029a06f11022sm26691105wrl.112.2023.01.16.06.41.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 16 Jan 2023 06:41:58 -0800 (PST) From: Bartosz Golaszewski To: Mark Brown , Francesco Dolcini , Max Krummenacher Cc: linux-spi@vger.kernel.org, linux-kernel@vger.kernel.org, Bartosz Golaszewski Subject: [PATCH -next] spi: spidev: fix a recursive locking error Date: Mon, 16 Jan 2023 15:41:49 +0100 Message-Id: <20230116144149.305560-1-brgl@bgdev.pl> X-Mailer: git-send-email 2.37.2 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-spi@vger.kernel.org From: Bartosz Golaszewski When calling spidev_message() from the one of the ioctl() callbacks, the spi_lock is already taken. When we then end up calling spidev_sync(), we get the following splat: [ 214.047619] [ 214.049198] ============================================ [ 214.054533] WARNING: possible recursive locking detected [ 214.059858] 6.2.0-rc3-0.0.0-devel+git.97ec4d559d93 #1 Not tainted [ 214.065969] -------------------------------------------- [ 214.071290] spidev_test/1454 is trying to acquire lock: [ 214.076530] c4925dbc (&spidev->spi_lock){+.+.}-{3:3}, at: spidev_ioctl+0x8e0/0xab8 [ 214.084164] [ 214.084164] but task is already holding lock: [ 214.090007] c4925dbc (&spidev->spi_lock){+.+.}-{3:3}, at: spidev_ioctl+0x44/0xab8 [ 214.097537] [ 214.097537] other info that might help us debug this: [ 214.104075] Possible unsafe locking scenario: [ 214.104075] [ 214.110004] CPU0 [ 214.112461] ---- [ 214.114916] lock(&spidev->spi_lock); [ 214.118687] lock(&spidev->spi_lock); [ 214.122457] [ 214.122457] *** DEADLOCK *** [ 214.122457] [ 214.128386] May be due to missing lock nesting notation [ 214.128386] [ 214.135183] 2 locks held by spidev_test/1454: [ 214.139553] #0: c4925dbc (&spidev->spi_lock){+.+.}-{3:3}, at: spidev_ioctl+0x44/0xab8 [ 214.147524] #1: c4925e14 (&spidev->buf_lock){+.+.}-{3:3}, at: spidev_ioctl+0x70/0xab8 [ 214.155493] [ 214.155493] stack backtrace: [ 214.159861] CPU: 0 PID: 1454 Comm: spidev_test Not tainted 6.2.0-rc3-0.0.0-devel+git.97ec4d559d93 #1 [ 214.169012] Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree) [ 214.175555] unwind_backtrace from show_stack+0x10/0x14 [ 214.180819] show_stack from dump_stack_lvl+0x60/0x90 [ 214.185900] dump_stack_lvl from __lock_acquire+0x874/0x2858 [ 214.191584] __lock_acquire from lock_acquire+0xfc/0x378 [ 214.196918] lock_acquire from __mutex_lock+0x9c/0x8a8 [ 214.202083] __mutex_lock from mutex_lock_nested+0x1c/0x24 [ 214.207597] mutex_lock_nested from spidev_ioctl+0x8e0/0xab8 [ 214.213284] spidev_ioctl from sys_ioctl+0x4d0/0xe2c [ 214.218277] sys_ioctl from ret_fast_syscall+0x0/0x1c [ 214.223351] Exception stack(0xe75cdfa8 to 0xe75cdff0) [ 214.228422] dfa0: 00000000 00001000 00000003 40206b00 bee266e8 bee266e0 [ 214.236617] dfc0: 00000000 00001000 006a71a0 00000036 004c0040 004bfd18 00000000 00000003 [ 214.244809] dfe0: 00000036 bee266c8 b6f16dc5 b6e8e5f6 Fix it by introducing an unlocked variant of spidev_sync() and calling it from spidev_message() while other users who don't check the spidev->spi's existence keep on using the locking flavor. Reported-by: Francesco Dolcini Fixes: 1f4d2dd45b6e ("spi: spidev: fix a race condition when accessing spidev->spi") Signed-off-by: Bartosz Golaszewski --- drivers/spi/spidev.c | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-) diff --git a/drivers/spi/spidev.c b/drivers/spi/spidev.c index 8ef22ebcde1f..892965ac8fdf 100644 --- a/drivers/spi/spidev.c +++ b/drivers/spi/spidev.c @@ -89,10 +89,22 @@ MODULE_PARM_DESC(bufsiz, "data bytes in biggest supported SPI message"); /*-------------------------------------------------------------------------*/ +static ssize_t +spidev_sync_unlocked(struct spi_device *spi, struct spi_message *message) +{ + ssize_t status; + + status = spi_sync(spi, message); + if (status == 0) + status = message->actual_length; + + return status; +} + static ssize_t spidev_sync(struct spidev_data *spidev, struct spi_message *message) { - int status; + ssize_t status; struct spi_device *spi; mutex_lock(&spidev->spi_lock); @@ -101,12 +113,10 @@ spidev_sync(struct spidev_data *spidev, struct spi_message *message) if (spi == NULL) status = -ESHUTDOWN; else - status = spi_sync(spi, message); - - if (status == 0) - status = message->actual_length; + status = spidev_sync_unlocked(spi, message); mutex_unlock(&spidev->spi_lock); + return status; } @@ -294,7 +304,7 @@ static int spidev_message(struct spidev_data *spidev, spi_message_add_tail(k_tmp, &msg); } - status = spidev_sync(spidev, &msg); + status = spidev_sync_unlocked(spidev->spi, &msg); if (status < 0) goto done;