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=-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 1BCC1C4338F for ; Wed, 25 Aug 2021 10:26:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0188361184 for ; Wed, 25 Aug 2021 10:26:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239961AbhHYK1W (ORCPT ); Wed, 25 Aug 2021 06:27:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40804 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239934AbhHYK1P (ORCPT ); Wed, 25 Aug 2021 06:27:15 -0400 Received: from mail-pl1-x630.google.com (mail-pl1-x630.google.com [IPv6:2607:f8b0:4864:20::630]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 51495C061757; Wed, 25 Aug 2021 03:26:29 -0700 (PDT) Received: by mail-pl1-x630.google.com with SMTP id b9so9677772plx.2; Wed, 25 Aug 2021 03:26:29 -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=mcrlqXx2veIFAPIuR1zZjjMGBGC3pLIA2IFrCCQwW8jK9wRON0L+mvneUtG9EWMRx+ 7d7b5AXWPfLm1KEB+5LTnOhEipuf9Di9/CY1lUxuUiDbu4v9A0doKF0Qm6poKea5VseM ko4jRSDZrGQ2WXvHQx7y+9kGiXJtIFws3WUyprbvinMgQ4n6Qa9xbgJM1o7xdsImwYt+ jNyeTWPF5243/7Qr5xB2lsXL4BXLNs/euuJ3AId/5+8W+fGHy+mP8eAJf8vH4fD8GXIa 7zXINxn+uv8DZbkky03Hg1aWUm/9c9gILHsj+0dX8m4Jw3w8F3dvcfvnnKkpIajiXCE7 0Z8Q== 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=mch9WhXWsuuHN9YF4y2YdhorQwfFDRGsMHa8ZvRZmbcsuuwqejQhROgHygk07GNgyQ yyEwg3owWn1+NEXRwPxvMVWe79t+ruAo3Oy99IndhpnXA1fyDfmTBY6gPVR5L/qTEkuv TPA2H0xrsIQr9XpM1jmLSRJENjFMzFxaxYSHHcSBIQgDNocikL0OWkkDEArRgff7ueCw hKPG1NegTaQPf66v2KJz1/fnlX8T33fE0zkUMPygp0Cbx6HuKKwyWdVT9cF1h/Jtb3LO veD3O9gtM9KZKkMqoh6M2yxZJk7phucLfJHrOYPFb0gHiL/a3nxLzEJhNJ3SZqD5SYcK pMSw== X-Gm-Message-State: AOAM5306evBofVa5uQWmaIhdTeL9U2327aQeHIvvYJq3hsWUun9KnXQm H5WonxQP6DpIp2OkbYyp7CE= X-Google-Smtp-Source: ABdhPJzePDrz0gmAXJF/b1c+ZQtAypG8eji/dWUqtQ+OfAnYEoiu9NXIpjQUuVh17nWzvMUuZRXSnQ== X-Received: by 2002:a17:902:bcc5:b0:133:1943:b48b with SMTP id o5-20020a170902bcc500b001331943b48bmr17088082pls.52.1629887188912; Wed, 25 Aug 2021 03:26:28 -0700 (PDT) Received: from localhost.localdomain ([118.200.190.93]) by smtp.gmail.com with ESMTPSA id t42sm10228377pfg.30.2021.08.25.03.26.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Aug 2021 03:26:28 -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 v6 3/7] drm: lock drm_global_mutex earlier in the ioctl handler Date: Wed, 25 Aug 2021 18:24:07 +0800 Message-Id: <20210825102411.1084220-4-desmondcheongzx@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210825102411.1084220-1-desmondcheongzx@gmail.com> References: <20210825102411.1084220-1-desmondcheongzx@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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); -- 2.25.1