From patchwork Mon Jul 12 04:35:06 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: 473268 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, URIBL_BLOCKED, 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 5676CC07E9E for ; Mon, 12 Jul 2021 04:36:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 43B6A610D0 for ; Mon, 12 Jul 2021 04:36:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231495AbhGLEi4 (ORCPT ); Mon, 12 Jul 2021 00:38:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59554 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230298AbhGLEi4 (ORCPT ); Mon, 12 Jul 2021 00:38:56 -0400 Received: from mail-pf1-x435.google.com (mail-pf1-x435.google.com [IPv6:2607:f8b0:4864:20::435]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7FFF9C0613DD; Sun, 11 Jul 2021 21:36:07 -0700 (PDT) Received: by mail-pf1-x435.google.com with SMTP id o201so10154338pfd.1; Sun, 11 Jul 2021 21:36:07 -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=CtdxbqSeV/2csKmNSvUS45gYT6/rPtvycxiemXQFqoE=; b=RkEVvjOYkpwdKOPg3pFGyZ+MmtY9Q6jyGy9uT18j8G2Y0B21jpq+qci03i9JMuQ+iv 3z/kr1Pf/aVNk9F5G8cbnU8ty+vr9/Dd4WL1XF9A1LmI8s6cHN4pAS6JC1o38oeJF5ek Eofy/TrzJ2b7IeTtAT7Ry1D9RINbF3rkJMgaHRIn5z/quGWmtgDA4WiBElGU2ZSXWb95 hZ6A+KULPqjOnqaADbeO1+cmK6skjVX4QzorBIolm1wJqxEgELwdZ1ZrS8h+RuhvSI4g 8bcmmqHqYyqjSrWhO4oBSFpXxHI4lW5yz/IM1saDLqFfDcDcNqDY9epj3nY6/nroIogX +q1A== 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=CtdxbqSeV/2csKmNSvUS45gYT6/rPtvycxiemXQFqoE=; b=NMgrJ3A6MXBomp/3xP/ZrFDss9iCAIFVFyqMYYihjb54IfwGdbP6IqV2Cj0s3gT4of shT95qrC2WOgbZ9dtDdLzCVOZKolMAqr0McRmhSPQIWtTsLersMWa8NMYq66XMV5y0oc n6jmXa2kQGQcO9FjgXtskL/2Nv8Cw60pzQh+Ww/KX6/Gf7lO7dcqG1/vcDmVcvTMo79E gCfO0wbBUVwbnE7e/ZTdKk09ZE9K85Fi9uekn77ZtnGJmWCsHxazN+izXlywfg7xUCoo siUQZRJPYygqWoLCRnmYSdbIb9FHOIkv0+5/SaWsXOXgpwaRL9spnlfqq1aaVrgCjRTN I7ug== X-Gm-Message-State: AOAM533c3+z2H/er3B34NWWnSGHqJhDa2EayDFwp1GGUm60TjL5OFyoQ JONd5tn+v9p5kP9sHfEMIkM= X-Google-Smtp-Source: ABdhPJz7q2t2Aox3iXnYKLt/9A+I+u5rTDJ6gGyg8eEi+vSuax0InwQFllAbLpOOEG/5WtqX4FbZPA== X-Received: by 2002:a63:de18:: with SMTP id f24mr45282752pgg.112.1626064567107; Sun, 11 Jul 2021 21:36:07 -0700 (PDT) Received: from localhost.localdomain ([118.200.190.93]) by smtp.gmail.com with ESMTPSA id n3sm14242764pfn.216.2021.07.11.21.36.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 11 Jul 2021 21:36:06 -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, intel-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org, skhan@linuxfoundation.org, gregkh@linuxfoundation.org, linux-kernel-mentees@lists.linuxfoundation.org, emil.l.velikov@gmail.com, Daniel Vetter Subject: [PATCH v8 3/5] drm: add a locked version of drm_is_current_master Date: Mon, 12 Jul 2021 12:35:06 +0800 Message-Id: <20210712043508.11584-4-desmondcheongzx@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210712043508.11584-1-desmondcheongzx@gmail.com> References: <20210712043508.11584-1-desmondcheongzx@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org While checking the master status of the DRM file in drm_is_current_master(), the device's master mutex should be held. Without the mutex, the pointer fpriv->master may be freed concurrently by another process calling drm_setmaster_ioctl(). This could lead to use-after-free errors when the pointer is subsequently dereferenced in drm_lease_owner(). The callers of drm_is_current_master() from drm_auth.c hold the device's master mutex, but external callers do not. Hence, we implement drm_is_current_master_locked() to be used within drm_auth.c, and modify drm_is_current_master() to grab the device's master mutex before checking the master status. Reported-by: Daniel Vetter Signed-off-by: Desmond Cheong Zhi Xi Reviewed-by: Emil Velikov --- drivers/gpu/drm/drm_auth.c | 51 ++++++++++++++++++++++++-------------- 1 file changed, 32 insertions(+), 19 deletions(-) diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c index f00e5abdbbf4..ab1863c5a5a0 100644 --- a/drivers/gpu/drm/drm_auth.c +++ b/drivers/gpu/drm/drm_auth.c @@ -61,6 +61,35 @@ * trusted clients. */ +static bool drm_is_current_master_locked(struct drm_file *fpriv) +{ + lockdep_assert_held_once(&fpriv->minor->dev->master_mutex); + + return fpriv->is_master && drm_lease_owner(fpriv->master) == fpriv->minor->dev->master; +} + +/** + * drm_is_current_master - checks whether @priv is the current master + * @fpriv: DRM file private + * + * Checks whether @fpriv is current master on its device. This decides whether a + * client is allowed to run DRM_MASTER IOCTLs. + * + * Most of the modern IOCTL which require DRM_MASTER are for kernel modesetting + * - the current master is assumed to own the non-shareable display hardware. + */ +bool drm_is_current_master(struct drm_file *fpriv) +{ + bool ret; + + mutex_lock(&fpriv->minor->dev->master_mutex); + ret = drm_is_current_master_locked(fpriv); + mutex_unlock(&fpriv->minor->dev->master_mutex); + + return ret; +} +EXPORT_SYMBOL(drm_is_current_master); + int drm_getmagic(struct drm_device *dev, void *data, struct drm_file *file_priv) { struct drm_auth *auth = data; @@ -223,7 +252,7 @@ int drm_setmaster_ioctl(struct drm_device *dev, void *data, if (ret) goto out_unlock; - if (drm_is_current_master(file_priv)) + if (drm_is_current_master_locked(file_priv)) goto out_unlock; if (dev->master) { @@ -272,7 +301,7 @@ int drm_dropmaster_ioctl(struct drm_device *dev, void *data, if (ret) goto out_unlock; - if (!drm_is_current_master(file_priv)) { + if (!drm_is_current_master_locked(file_priv)) { ret = -EINVAL; goto out_unlock; } @@ -321,7 +350,7 @@ void drm_master_release(struct drm_file *file_priv) if (file_priv->magic) idr_remove(&file_priv->master->magic_map, file_priv->magic); - if (!drm_is_current_master(file_priv)) + if (!drm_is_current_master_locked(file_priv)) goto out; drm_legacy_lock_master_cleanup(dev, master); @@ -342,22 +371,6 @@ void drm_master_release(struct drm_file *file_priv) mutex_unlock(&dev->master_mutex); } -/** - * drm_is_current_master - checks whether @priv is the current master - * @fpriv: DRM file private - * - * Checks whether @fpriv is current master on its device. This decides whether a - * client is allowed to run DRM_MASTER IOCTLs. - * - * Most of the modern IOCTL which require DRM_MASTER are for kernel modesetting - * - the current master is assumed to own the non-shareable display hardware. - */ -bool drm_is_current_master(struct drm_file *fpriv) -{ - return fpriv->is_master && drm_lease_owner(fpriv->master) == fpriv->minor->dev->master; -} -EXPORT_SYMBOL(drm_is_current_master); - /** * drm_master_get - reference a master pointer * @master: &struct drm_master