From patchwork Sun Jun 20 11:03:26 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: 464796 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, 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 6BB34C49361 for ; Sun, 20 Jun 2021 11:05:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5460B61153 for ; Sun, 20 Jun 2021 11:05:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229619AbhFTLH2 (ORCPT ); Sun, 20 Jun 2021 07:07:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35896 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229516AbhFTLH1 (ORCPT ); Sun, 20 Jun 2021 07:07:27 -0400 Received: from mail-pg1-x52d.google.com (mail-pg1-x52d.google.com [IPv6:2607:f8b0:4864:20::52d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EC991C061574; Sun, 20 Jun 2021 04:05:14 -0700 (PDT) Received: by mail-pg1-x52d.google.com with SMTP id v7so11727891pgl.2; Sun, 20 Jun 2021 04:05:14 -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=QdEeAyJvp98gW9MsCsFcUbBFLoaOp7KDNa8rsFezt8g=; b=HDFLYjYuPl+A+gCmumCr/IXehCHTQJ7xwyL+XPAfqocQ2F9fWvSf71X9VJcAJ5MpzT 4pYwWidiB24i9HR5dU7Oc0wqlaQGwcQdTAZ2xUoy6uODDq9bwf3h+lxhA3UyUvPctzI+ hDzLfazyWMGcfyv34x7YbE8jRVh9PkZ1PfQ43kwD7JDLLz6oBA6GkVOMszLJxcwuFnGn 4pRYwIu8K29E4/OKu+WD7XEFWQc62mjEwJOdx6b9UZvhxZG3m9Lm0PHr2/dD9q2HSrO0 cThFh6bhPtQu0P/fD5k3r1jiNmc3F5i9TaSJ3TrBAGxp3GXBBqR+u9639JCp9+FFPqcy Dp2g== 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=QdEeAyJvp98gW9MsCsFcUbBFLoaOp7KDNa8rsFezt8g=; b=OYuhNv00ledOBK1TSuCCTI+xC2xiYqFLC/qbEuiTKMgQNfRlWyO+WXtdkdmYQALyYF r9j5H9D7Uz4iyLt8/t6MXEOMfy5ecdyBUi54bh2hl4hnyT3BxDm+nYImSRBUag44qNo9 rO7KikhyvE4pzy0rOYE7yV8GIokEPzyw9FZ3iucFCyCxqU2jhGCLtABKlwVSKZaF5R/F 3BsB99wlbWA5f9Uu3YFnUdEERfBFDrr1tXOFHjkhxcma7N4kZBmbBDhZv/Dwbjl+bLai 3o8m2w0uD/+10/TXxC8CenikdjLZlJcvqOhbXtZrSyV6EArPjVYPwG+faxLoYVoWpdSS pb8A== X-Gm-Message-State: AOAM533e233IkKajJdkekbH5QG2uXcxRehcOjG53pdKuEVTTTVrYZgbv yG02hSTk/nJ0pXZmGSrrDbE= X-Google-Smtp-Source: ABdhPJyvmyogMygAVd6ehpn0EVt1WfMUiS3Btsf41oBLFjGCz1h+5sSm06GPr5hivd9r9vhvCvtLcw== X-Received: by 2002:a05:6a00:1344:b029:2f6:5ce3:218e with SMTP id k4-20020a056a001344b02902f65ce3218emr14349473pfu.80.1624187114436; Sun, 20 Jun 2021 04:05:14 -0700 (PDT) Received: from localhost.localdomain ([118.200.190.93]) by smtp.gmail.com with ESMTPSA id h22sm2644876pfc.21.2021.06.20.04.05.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 20 Jun 2021 04:05:14 -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, 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 v3 1/2] drm: add a locked version of drm_is_current_master Date: Sun, 20 Jun 2021 19:03:26 +0800 Message-Id: <20210620110327.4964-2-desmondcheongzx@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210620110327.4964-1-desmondcheongzx@gmail.com> References: <20210620110327.4964-1-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 232abbba3686..86d4b72e95cb 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->master->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->master->dev->master_mutex); + ret = drm_is_current_master_locked(fpriv); + mutex_unlock(&fpriv->master->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