From patchwork Thu Aug 26 02:01:18 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: 12458825 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=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 9FEB4C432BE for ; Thu, 26 Aug 2021 02:02:36 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 604A7610C9 for ; Thu, 26 Aug 2021 02:02:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 604A7610C9 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id C240A6E487; Thu, 26 Aug 2021 02:02:35 +0000 (UTC) Received: from mail-pl1-x635.google.com (mail-pl1-x635.google.com [IPv6:2607:f8b0:4864:20::635]) by gabe.freedesktop.org (Postfix) with ESMTPS id D82946E486; Thu, 26 Aug 2021 02:02:34 +0000 (UTC) Received: by mail-pl1-x635.google.com with SMTP id m4so820523pll.0; Wed, 25 Aug 2021 19:02:34 -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=CT7h6MBpAMDIzIkV8lMUMCjYQ166pfsg2+w0kUZlShHVyArnL+WjVrSIfMoU4JnlZ6 6bPBRWqj0e3eOeUtjM3d24seYloYJPfjNpUKpWtnwUkUHD6iUXCPSX44W8kUrA0CGCgt LtQJZd4cGVCCUpyQZBLrpKgjNSmayak1iXZaJS2CMPIjouy2VJhpTuBbpdd/YHtD6beK dd04Kl0M4LQ4Yfs1VgdcmIMO8bNiWpLP54v0OHeYyVExW2djCkhTl9Psq4/em9ZKjlCK LzqXnyTFpjCOtvtKeHELyI3nKD2pD6pAtrDa+6RC9JtHGqG6hggk8IUfp0klqHWQrpPd sJlA== 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=r9Kt1w8jWlsFq3vc2HkNkqzdSGBblUDP/rSX2Fd3C5FEbTtQ+1jWjepVP2T6i3AtP5 T4LSJ76G8D+dlyMMjGJkNsa9n4q5Pd2ZwvVYae+IQomtlPSiWU9nqIlqK54SffxSE8tt zFxp5dPMt1Tl+PBBxND2GtRH4vD4e/DzI4sJ8BPKrA1mHr/w3kDNiOMX6qiYROm40g69 9yeA2gB/D+P7WpCP+N5c7vv5rjlgvkAiUm8tu1xCe1t2cofeTXeLP7AuYb5V9g6momfg L0Xu0iZhRpbyM0nQAKOJfiyV6WChmwXsilDranemhS1jIg2afzycbgv30SYqHL5uu81i rrLA== X-Gm-Message-State: AOAM531/zcnA1H+w0Ckqy7GEOhpcpJeqjsgiXHeaCPU8OvLmbAvayDKL RdLtVOotFq7Vd2U9+TdWd0Y= X-Google-Smtp-Source: ABdhPJzmR2y3ikzBJknZrPk9wq+3ldlOQum+iet+txHL0F0oPreTZxXgS8lPn2WuOpIGYazbm9/lAw== X-Received: by 2002:a17:90a:9411:: with SMTP id r17mr1401311pjo.49.1629943354485; Wed, 25 Aug 2021 19:02:34 -0700 (PDT) Received: from localhost.localdomain ([118.200.190.93]) by smtp.gmail.com with ESMTPSA id i11sm721973pjj.19.2021.08.25.19.02.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Aug 2021 19:02:34 -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 v8 3/7] drm: lock drm_global_mutex earlier in the ioctl handler Date: Thu, 26 Aug 2021 10:01:18 +0800 Message-Id: <20210826020122.1488002-4-desmondcheongzx@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210826020122.1488002-1-desmondcheongzx@gmail.com> References: <20210826020122.1488002-1-desmondcheongzx@gmail.com> MIME-Version: 1.0 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" 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);