From patchwork Wed Aug 25 14:22:01 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Desmond Cheong Zhi Xi X-Patchwork-Id: 503135 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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 8F7B0C4338F for ; Wed, 25 Aug 2021 14:25:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6A72E61073 for ; Wed, 25 Aug 2021 14:25:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241394AbhHYO0M (ORCPT ); Wed, 25 Aug 2021 10:26:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39678 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241406AbhHYOYE (ORCPT ); Wed, 25 Aug 2021 10:24:04 -0400 Received: from mail-pj1-x102d.google.com (mail-pj1-x102d.google.com [IPv6:2607:f8b0:4864:20::102d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 80271C0617AE; Wed, 25 Aug 2021 07:23:14 -0700 (PDT) Received: by mail-pj1-x102d.google.com with SMTP id 28-20020a17090a031cb0290178dcd8a4d1so4065075pje.0; Wed, 25 Aug 2021 07:23:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=P/HLeCdm1ln+WDWlHx3gbH2c2TGPxEmJ7R7sNcfLOXw=; b=mtusQYTEk4rQj6pUM/lQl90/Exg1KKKi8S2bYy3beGnr6kEdJP6PRRWD2uPXm6vUTd acRmdwv1/IRfDGhkvgFSgxkhY1u5OZ9A2cdbTpq2r/Xm+wBxHNYVDcgBZCAqcABPAYfv 4ebW71RUeuvZTYhf148UsxkEr/hPn3G0E4Ki1dTPAQf0K+VfY1ljuPmezRzWhABmkfFY n5gRqnw2GeT/Jb0RtFtX4rmX9JHuCdCfnY+jreWEZnHqE1UCvNrP0AgTb5a4p1E9NZVD P5rY4Re6UlxNz6kJWStphT7vrrT4Q+YZRZwM5+NrMKRe2asFn9/XcfQ3Wl70sM5W4VLA Q4gg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=P/HLeCdm1ln+WDWlHx3gbH2c2TGPxEmJ7R7sNcfLOXw=; b=M2iRDbCHjFT4X5zVdFyvLp9him859OBMIEltMxPuziJhj8g+sur5GK95Opeza4+YDP /rpittagaAcUDN1qgvqg2dp7g3ysKWP7NVDebPFODxgmO0Of3otVPRCeDgaAiz0sLpu7 dcAraJCMhWljhuXvRXCaWyAMlCUoCXA6vhabvShuVegQ5fdYSJwORfALwcZrDIkkWZ9M +0mu6ZDJLksnvCFUOT3vb15RDfynUyWko4qVKyjdnC9tVkDIA2cYDx2WYbTAIkaIaLIz aXNYZ8UG7+mqaawjiGsrVd9iqL219U6HZAb1+6Z7oWRnsQQfruch1f1g/KpZPQMnDV48 0i3Q== X-Gm-Message-State: AOAM533XVZQqclMHjEvBgAoZI03pgZRAbOh+PIztBY8VJ/W6YBXt/kat FbHwPS03nY3b+kicCbqKc9g= X-Google-Smtp-Source: ABdhPJzQnYaYnevO8OAbWnnCMUEI3RT7xGhLZk59sUi6P6kDpoTEqTSVhl51BWqj4TosZGsYPBXG9A== X-Received: by 2002:a17:902:850a:b029:12c:8da9:8bd2 with SMTP id bj10-20020a170902850ab029012c8da98bd2mr38657273plb.58.1629901394081; Wed, 25 Aug 2021 07:23:14 -0700 (PDT) Received: from localhost.localdomain ([118.200.190.93]) by smtp.gmail.com with ESMTPSA id n3sm54431pfo.101.2021.08.25.07.23.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Aug 2021 07:23:13 -0700 (PDT) From: Desmond Cheong Zhi Xi To: maarten.lankhorst@linux.intel.com, mripard@kernel.org, tzimmermann@suse.de, airlied@linux.ie, daniel@ffwll.ch, sumit.semwal@linaro.org, christian.koenig@amd.com, jani.nikula@linux.intel.com, joonas.lahtinen@linux.intel.com, rodrigo.vivi@intel.com, chris@chris-wilson.co.uk, ville.syrjala@linux.intel.com, matthew.auld@intel.com, dan.carpenter@oracle.com, tvrtko.ursulin@intel.com, matthew.d.roper@intel.com, lucas.demarchi@intel.com, karthik.b.s@intel.com, jose.souza@intel.com, manasi.d.navare@intel.com, airlied@redhat.com, aditya.swarup@intel.com, andrescj@chromium.org, linux-graphics-maintainer@vmware.com, zackr@vmware.com Cc: Desmond Cheong Zhi Xi , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, intel-gfx@lists.freedesktop.org, linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org, skhan@linuxfoundation.org, gregkh@linuxfoundation.org, linux-kernel-mentees@lists.linuxfoundation.org Subject: [PATCH v7 3/7] drm: lock drm_global_mutex earlier in the ioctl handler Date: Wed, 25 Aug 2021 22:22:01 +0800 Message-Id: <20210825142205.1376789-4-desmondcheongzx@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210825142205.1376789-1-desmondcheongzx@gmail.com> References: <20210825142205.1376789-1-desmondcheongzx@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org In a future patch, a read lock on drm_device.master_rwsem is held in the ioctl handler before the check for ioctl permissions. However, this inverts the lock hierarchy of drm_global_mutex --> master_rwsem. To avoid this, we do some prep work to grab the drm_global_mutex before checking for ioctl permissions. Signed-off-by: Desmond Cheong Zhi Xi --- drivers/gpu/drm/drm_ioctl.c | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c index d25713b09b80..158629d88319 100644 --- a/drivers/gpu/drm/drm_ioctl.c +++ b/drivers/gpu/drm/drm_ioctl.c @@ -772,19 +772,19 @@ long drm_ioctl_kernel(struct file *file, drm_ioctl_t *func, void *kdata, if (drm_dev_is_unplugged(dev)) return -ENODEV; + /* Enforce sane locking for modern driver ioctls. */ + if (unlikely(drm_core_check_feature(dev, DRIVER_LEGACY)) && !(flags & DRM_UNLOCKED)) + mutex_lock(&drm_global_mutex); + retcode = drm_ioctl_permit(flags, file_priv); if (unlikely(retcode)) - return retcode; + goto out; - /* Enforce sane locking for modern driver ioctls. */ - if (likely(!drm_core_check_feature(dev, DRIVER_LEGACY)) || - (flags & DRM_UNLOCKED)) - retcode = func(dev, kdata, file_priv); - else { - mutex_lock(&drm_global_mutex); - retcode = func(dev, kdata, file_priv); + retcode = func(dev, kdata, file_priv); + +out: + if (unlikely(drm_core_check_feature(dev, DRIVER_LEGACY)) && !(flags & DRM_UNLOCKED)) mutex_unlock(&drm_global_mutex); - } return retcode; } EXPORT_SYMBOL(drm_ioctl_kernel);