From patchwork Mon Aug 23 17:14:34 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: 12453307 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=-15.7 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 EE30DC432BE for ; Mon, 23 Aug 2021 17:15:32 +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 BC55961206 for ; Mon, 23 Aug 2021 17:15:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org BC55961206 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 C8C9F6E07D; Mon, 23 Aug 2021 17:15:31 +0000 (UTC) Received: from mail-pf1-x429.google.com (mail-pf1-x429.google.com [IPv6:2607:f8b0:4864:20::429]) by gabe.freedesktop.org (Postfix) with ESMTPS id C812A6E069; Mon, 23 Aug 2021 17:15:29 +0000 (UTC) Received: by mail-pf1-x429.google.com with SMTP id 18so15950023pfh.9; Mon, 23 Aug 2021 10:15:29 -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=c0f4kiiXc4IkYgZ7SwV50fvg9X1ZxF8YmeWTnH1aY4zr7f7CxUhhKSV/ZxhYEciPsx R4qVFbmzrhrtFLWu5p5Y0++tTcd6CaIj04UjTLFpXvsk9ker44OElUT1FAhJ1Rt0VW+L kJjfeN5Gn7i6bWpucmWiFYyQ16P3Jy332p1OBTQKhgyhWGok75i5BFP08s/R0+IH7OWo NtrYk744ZrR0r4l/25XjPCpwbOubap2eD0VpfKj1KT4MhXwPEorZId01Rru6W+3wAJk1 h5BxeL35p/7pwLyuFfPvEvQyytrwmRi+vPiLjPoshVtby2FB5ccCGeT+9IpVO3fPjaEI IBsA== 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=jc0fIsYTvcH5jAKBGOHfecn9pt/ac0CV4EtyIRm6XpxTJl65t8YbpL4ZODIhdUj0sv Odm5QlfNfE+ZnaJlqfhhanAEt/GL6duZO/CrbpcK7HxnGnXuy4ftyGsuZT8vCJ/eb3WV b0EvJD4JL/zen+aNAEsdDjeqtipQXT/guBWdLGFvglYpQXIQS2QiUM7ZjHZ12f22q1sD /oLqZPV7+ukgjGB1MIEEk44/ClQb9FbDbRA8huqvAM0pU5rNGqaoKshyyPzshAFKnwSK 7jBhE2AsoU10aTdP2xqV1z+TS9YQWGcC7yexJ5gRvZapD8JJDaUyIrFvlffTDROnFyZD rBtw== X-Gm-Message-State: AOAM531WYesggzYwg3OxmacLIndG+DnF9G3O9AAWPdvKfAi0O8m+VZvz BNr6hk8RMbzUtmGFR949cRM= X-Google-Smtp-Source: ABdhPJxHInaVZCTCItEa4Eu561qYx8GvC70vOUyW+CghTAjRug2jVLVxRcc+W6Xrpc1RMGrYbv9O9A== X-Received: by 2002:aa7:94ac:0:b0:3e0:f21a:e6ff with SMTP id a12-20020aa794ac000000b003e0f21ae6ffmr33941216pfl.76.1629738929457; Mon, 23 Aug 2021 10:15:29 -0700 (PDT) Received: from localhost.localdomain ([118.200.190.93]) by smtp.gmail.com with ESMTPSA id q4sm14290830pjd.52.2021.08.23.10.15.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 23 Aug 2021 10:15:29 -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 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 v5 3/6] drm: lock drm_global_mutex earlier in the ioctl handler Date: Tue, 24 Aug 2021 01:14:34 +0800 Message-Id: <20210823171437.829404-4-desmondcheongzx@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210823171437.829404-1-desmondcheongzx@gmail.com> References: <20210823171437.829404-1-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);