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 F021FC11F67 for ; Tue, 29 Jun 2021 03:38:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DB60D61D3C for ; Tue, 29 Jun 2021 03:38:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232025AbhF2Dks (ORCPT ); Mon, 28 Jun 2021 23:40:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42298 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232021AbhF2Dkm (ORCPT ); Mon, 28 Jun 2021 23:40:42 -0400 Received: from mail-pj1-x1030.google.com (mail-pj1-x1030.google.com [IPv6:2607:f8b0:4864:20::1030]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 30644C061767; Mon, 28 Jun 2021 20:38:15 -0700 (PDT) Received: by mail-pj1-x1030.google.com with SMTP id l11so11532822pji.5; Mon, 28 Jun 2021 20:38:15 -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=e89hcvZxRiZ5Blo85VTbkHd9GG4LouPsbTHXMkcWyoA=; b=G0Cx3O4RZRxIvja4xrrosgMNsGwe3/2+TREWfgokq76RrCJkB5N527/IWVOagomnju YdkO1XiD2OR43x6xJZwQWUBqeK4dVKcaNZG8Px6/tM+rOxokSJtPfp8cF+nSQb0aKsTj p6Pf0nvV7JT+1zAqBYli6UrVvggPLZAX/ho4lvghsbZS7fnaoctoHNaj4lv3P860GmeG 2eSxPkmEhMoeF+N4mmjQiXN/s9nBHRQ9BzjewfVLnaQ6g6dWsA4egGKFkiDy5x0do/gr y7rkbxsjkVxu6iwzGKnunDYQTZFJipjP0Hx+qhdrgADvHyX2sjbh27w8S7D2WgNAvzVF 1uCg== 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=e89hcvZxRiZ5Blo85VTbkHd9GG4LouPsbTHXMkcWyoA=; b=dk57l354IuedPQMXJd2/X35VZyH0GAJpCvczeQ4U7U+0MVzwi7RWfYAbQIkYcage/j 61nRELeytlO9UTjWKbOTWDVQMc3kFH1EkkOp42hPXjznUjWSlrWb2gdjI1+ityYNwu4F C43vkGnSqW7oNR3oXu2HRVq7sugx3ad8+e52rKJpoJK/WL78dTDUxtXCqj1mGdwBQpzb Cy9R1MIXIX8qc9isF/B/PFvFoVvD9/MkXdQP3tjds0CF/3Xoid+x1TGLnPWcMBfwIsk8 5rcRrY2TRMHoXG0XY9VP913MY6I39PSWj82UWpKVi4cdhXJeJZvHVzXQWICW0MHrlEXg H7+w== X-Gm-Message-State: AOAM531nwEJeKAAxIm9su3uS54rge61cRFnG21niHWCZkklEOq4vaLN0 F9JFSNOi7CK8huL+TYGDTxM= X-Google-Smtp-Source: ABdhPJwZLih7PT7j6HnuHpFvYYxk6ZWBH33LNHYAYqH4Y9iprMVib64xa1z8fIpPEJJZTu+1KGsMLg== X-Received: by 2002:a17:902:a50f:b029:11a:b033:e158 with SMTP id s15-20020a170902a50fb029011ab033e158mr25760151plq.26.1624937894622; Mon, 28 Jun 2021 20:38:14 -0700 (PDT) Received: from localhost.localdomain ([118.200.190.93]) by smtp.gmail.com with ESMTPSA id d129sm14769076pfd.218.2021.06.28.20.38.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Jun 2021 20:38:14 -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, 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 v5 3/3] drm: protect drm_master pointers in drm_lease.c Date: Tue, 29 Jun 2021 11:37:06 +0800 Message-Id: <20210629033706.20537-4-desmondcheongzx@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210629033706.20537-1-desmondcheongzx@gmail.com> References: <20210629033706.20537-1-desmondcheongzx@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Currently, direct copies of drm_file->master pointers should be protected by drm_device.master_mutex when being dereferenced. This is because drm_file->master is not invariant for the lifetime of drm_file. If drm_file is not the creator of master, then drm_file->is_master is false, and a call to drm_setmaster_ioctl will invoke drm_new_set_master, which then allocates a new master for drm_file and puts the old master. Thus, without holding drm_device.master_mutex, the old value of drm_file->master could be freed while it is being used by another concurrent process. In drm_lease.c, there are multiple instances where drm_file->master is accessed and dereferenced while drm_device.master_mutex is not held. This makes drm_lease.c vulnerable to use-after-free bugs. We address this issue in 3 ways: 1. Clarify in the kerneldoc that drm_file->master is protected by drm_device.master_mutex. 2. Add a new drm_file_get_master() function that calls drm_master_get on drm_file->master while holding on to drm_device.master_mutex. Since drm_master_get increments the reference count of master, this prevents master from being freed until we unreference it with drm_master_put. 3. In each case where drm_file->master is directly accessed and eventually dereferenced in drm_lease.c, we wrap the access in a call to the new drm_file_get_master function, then unreference the master pointer once we are done using it. Reported-by: Daniel Vetter Signed-off-by: Desmond Cheong Zhi Xi --- drivers/gpu/drm/drm_auth.c | 25 ++++++++++++ drivers/gpu/drm/drm_lease.c | 77 +++++++++++++++++++++++++++---------- include/drm/drm_auth.h | 1 + include/drm/drm_file.h | 15 ++++++-- 4 files changed, 95 insertions(+), 23 deletions(-) diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c index ab1863c5a5a0..c36a0b72be26 100644 --- a/drivers/gpu/drm/drm_auth.c +++ b/drivers/gpu/drm/drm_auth.c @@ -384,6 +384,31 @@ struct drm_master *drm_master_get(struct drm_master *master) } EXPORT_SYMBOL(drm_master_get); +/** + * drm_file_get_master - reference &drm_file.master of @file_priv + * @file_priv: DRM file private + * + * Increments the reference count of @file_priv's &drm_file.master and returns + * the &drm_file.master. If @file_priv has no &drm_file.master, returns NULL. + * + * Master pointers returned from this function should be unreferenced using + * drm_master_put(). + */ +struct drm_master *drm_file_get_master(struct drm_file *file_priv) +{ + struct drm_master *master = NULL; + + mutex_lock(&file_priv->minor->dev->master_mutex); + if (!file_priv->master) + goto unlock; + master = drm_master_get(file_priv->master); + +unlock: + mutex_unlock(&file_priv->minor->dev->master_mutex); + return master; +} +EXPORT_SYMBOL(drm_file_get_master); + static void drm_master_destroy(struct kref *kref) { struct drm_master *master = container_of(kref, struct drm_master, refcount); diff --git a/drivers/gpu/drm/drm_lease.c b/drivers/gpu/drm/drm_lease.c index 00fb433bcef1..cdcc87fa9685 100644 --- a/drivers/gpu/drm/drm_lease.c +++ b/drivers/gpu/drm/drm_lease.c @@ -106,10 +106,19 @@ static bool _drm_has_leased(struct drm_master *master, int id) */ bool _drm_lease_held(struct drm_file *file_priv, int id) { - if (!file_priv || !file_priv->master) + bool ret; + struct drm_master *master; + + if (!file_priv) return true; - return _drm_lease_held_master(file_priv->master, id); + master = drm_file_get_master(file_priv); + if (master == NULL) + return true; + ret = _drm_lease_held_master(master, id); + drm_master_put(&master); + + return ret; } /** @@ -128,13 +137,20 @@ bool drm_lease_held(struct drm_file *file_priv, int id) struct drm_master *master; bool ret; - if (!file_priv || !file_priv->master || !file_priv->master->lessor) + if (!file_priv) return true; - master = file_priv->master; + master = drm_file_get_master(file_priv); + if (master == NULL) + return true; + if (!master->lessor) { + drm_master_put(&master); + return true; + } mutex_lock(&master->dev->mode_config.idr_mutex); ret = _drm_lease_held_master(master, id); mutex_unlock(&master->dev->mode_config.idr_mutex); + drm_master_put(&master); return ret; } @@ -154,10 +170,16 @@ uint32_t drm_lease_filter_crtcs(struct drm_file *file_priv, uint32_t crtcs_in) int count_in, count_out; uint32_t crtcs_out = 0; - if (!file_priv || !file_priv->master || !file_priv->master->lessor) + if (!file_priv) return crtcs_in; - master = file_priv->master; + master = drm_file_get_master(file_priv); + if (master == NULL) + return crtcs_in; + if (!master->lessor) { + drm_master_put(&master); + return crtcs_in; + } dev = master->dev; count_in = count_out = 0; @@ -176,6 +198,7 @@ uint32_t drm_lease_filter_crtcs(struct drm_file *file_priv, uint32_t crtcs_in) count_in++; } mutex_unlock(&master->dev->mode_config.idr_mutex); + drm_master_put(&master); return crtcs_out; } @@ -489,7 +512,7 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, size_t object_count; int ret = 0; struct idr leases; - struct drm_master *lessor = lessor_priv->master; + struct drm_master *lessor; struct drm_master *lessee = NULL; struct file *lessee_file = NULL; struct file *lessor_file = lessor_priv->filp; @@ -501,12 +524,6 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, if (!drm_core_check_feature(dev, DRIVER_MODESET)) return -EOPNOTSUPP; - /* Do not allow sub-leases */ - if (lessor->lessor) { - DRM_DEBUG_LEASE("recursive leasing not allowed\n"); - return -EINVAL; - } - /* need some objects */ if (cl->object_count == 0) { DRM_DEBUG_LEASE("no objects in lease\n"); @@ -518,12 +535,22 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, return -EINVAL; } + lessor = drm_file_get_master(lessor_priv); + /* Do not allow sub-leases */ + if (lessor->lessor) { + DRM_DEBUG_LEASE("recursive leasing not allowed\n"); + ret = -EINVAL; + goto out_lessor; + } + object_count = cl->object_count; object_ids = memdup_user(u64_to_user_ptr(cl->object_ids), array_size(object_count, sizeof(__u32))); - if (IS_ERR(object_ids)) - return PTR_ERR(object_ids); + if (IS_ERR(object_ids)) { + ret = PTR_ERR(object_ids); + goto out_lessor; + } idr_init(&leases); @@ -534,14 +561,15 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, if (ret) { DRM_DEBUG_LEASE("lease object lookup failed: %i\n", ret); idr_destroy(&leases); - return ret; + goto out_lessor; } /* Allocate a file descriptor for the lease */ fd = get_unused_fd_flags(cl->flags & (O_CLOEXEC | O_NONBLOCK)); if (fd < 0) { idr_destroy(&leases); - return fd; + ret = fd; + goto out_lessor; } DRM_DEBUG_LEASE("Creating lease\n"); @@ -577,6 +605,7 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, /* Hook up the fd */ fd_install(fd, lessee_file); + drm_master_put(&lessor); DRM_DEBUG_LEASE("drm_mode_create_lease_ioctl succeeded\n"); return 0; @@ -586,6 +615,8 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, out_leases: put_unused_fd(fd); +out_lessor: + drm_master_put(&lessor); DRM_DEBUG_LEASE("drm_mode_create_lease_ioctl failed: %d\n", ret); return ret; } @@ -608,7 +639,7 @@ int drm_mode_list_lessees_ioctl(struct drm_device *dev, struct drm_mode_list_lessees *arg = data; __u32 __user *lessee_ids = (__u32 __user *) (uintptr_t) (arg->lessees_ptr); __u32 count_lessees = arg->count_lessees; - struct drm_master *lessor = lessor_priv->master, *lessee; + struct drm_master *lessor, *lessee; int count; int ret = 0; @@ -619,6 +650,7 @@ int drm_mode_list_lessees_ioctl(struct drm_device *dev, if (!drm_core_check_feature(dev, DRIVER_MODESET)) return -EOPNOTSUPP; + lessor = drm_file_get_master(lessor_priv); DRM_DEBUG_LEASE("List lessees for %d\n", lessor->lessee_id); mutex_lock(&dev->mode_config.idr_mutex); @@ -642,6 +674,7 @@ int drm_mode_list_lessees_ioctl(struct drm_device *dev, arg->count_lessees = count; mutex_unlock(&dev->mode_config.idr_mutex); + drm_master_put(&lessor); return ret; } @@ -661,7 +694,7 @@ int drm_mode_get_lease_ioctl(struct drm_device *dev, struct drm_mode_get_lease *arg = data; __u32 __user *object_ids = (__u32 __user *) (uintptr_t) (arg->objects_ptr); __u32 count_objects = arg->count_objects; - struct drm_master *lessee = lessee_priv->master; + struct drm_master *lessee; struct idr *object_idr; int count; void *entry; @@ -675,6 +708,7 @@ int drm_mode_get_lease_ioctl(struct drm_device *dev, if (!drm_core_check_feature(dev, DRIVER_MODESET)) return -EOPNOTSUPP; + lessee = drm_file_get_master(lessee_priv); DRM_DEBUG_LEASE("get lease for %d\n", lessee->lessee_id); mutex_lock(&dev->mode_config.idr_mutex); @@ -702,6 +736,7 @@ int drm_mode_get_lease_ioctl(struct drm_device *dev, arg->count_objects = count; mutex_unlock(&dev->mode_config.idr_mutex); + drm_master_put(&lessee); return ret; } @@ -720,7 +755,7 @@ int drm_mode_revoke_lease_ioctl(struct drm_device *dev, void *data, struct drm_file *lessor_priv) { struct drm_mode_revoke_lease *arg = data; - struct drm_master *lessor = lessor_priv->master; + struct drm_master *lessor; struct drm_master *lessee; int ret = 0; @@ -730,6 +765,7 @@ int drm_mode_revoke_lease_ioctl(struct drm_device *dev, if (!drm_core_check_feature(dev, DRIVER_MODESET)) return -EOPNOTSUPP; + lessor = drm_file_get_master(lessor_priv); mutex_lock(&dev->mode_config.idr_mutex); lessee = _drm_find_lessee(lessor, arg->lessee_id); @@ -750,6 +786,7 @@ int drm_mode_revoke_lease_ioctl(struct drm_device *dev, fail: mutex_unlock(&dev->mode_config.idr_mutex); + drm_master_put(&lessor); return ret; } diff --git a/include/drm/drm_auth.h b/include/drm/drm_auth.h index 6bf8b2b78991..f99d3417f304 100644 --- a/include/drm/drm_auth.h +++ b/include/drm/drm_auth.h @@ -107,6 +107,7 @@ struct drm_master { }; struct drm_master *drm_master_get(struct drm_master *master); +struct drm_master *drm_file_get_master(struct drm_file *file_priv); void drm_master_put(struct drm_master **master); bool drm_is_current_master(struct drm_file *fpriv); diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h index b81b3bfb08c8..e9931fca4ab7 100644 --- a/include/drm/drm_file.h +++ b/include/drm/drm_file.h @@ -226,9 +226,18 @@ struct drm_file { /** * @master: * - * Master this node is currently associated with. Only relevant if - * drm_is_primary_client() returns true. Note that this only - * matches &drm_device.master if the master is the currently active one. + * Master this node is currently associated with. Protected by struct + * &drm_device.master_mutex. + * + * Only relevant if drm_is_primary_client() returns true. Note that + * this only matches &drm_device.master if the master is the currently + * active one. + * + * When obtaining a copy of this pointer, it is recommended to either + * hold struct &drm_device.master_mutex for the duration of the + * pointer's use, or to use drm_file_get_master() if struct + * &drm_device.master_mutex is not currently held and there is no other + * need to hold it. This prevents @master from being freed during use. * * See also @authentication and @is_master and the :ref:`section on * primary nodes and authentication `. -- 2.25.1 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=-13.5 required=3.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED,DKIM_INVALID,DKIM_SIGNED,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 BBFD1C11F67 for ; Tue, 29 Jun 2021 03:38:18 +0000 (UTC) Received: from smtp1.osuosl.org (smtp1.osuosl.org [140.211.166.138]) (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 76A3D61D3C for ; 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Mon, 28 Jun 2021 20:38:14 -0700 (PDT) Received: from localhost.localdomain ([118.200.190.93]) by smtp.gmail.com with ESMTPSA id d129sm14769076pfd.218.2021.06.28.20.38.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Jun 2021 20:38:14 -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 Subject: [PATCH v5 3/3] drm: protect drm_master pointers in drm_lease.c Date: Tue, 29 Jun 2021 11:37:06 +0800 Message-Id: <20210629033706.20537-4-desmondcheongzx@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210629033706.20537-1-desmondcheongzx@gmail.com> References: <20210629033706.20537-1-desmondcheongzx@gmail.com> MIME-Version: 1.0 Cc: Daniel Vetter , intel-gfx@lists.freedesktop.org, emil.l.velikov@gmail.com, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, Desmond Cheong Zhi Xi , linux-kernel-mentees@lists.linuxfoundation.org, linux-media@vger.kernel.org X-BeenThere: linux-kernel-mentees@lists.linuxfoundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-kernel-mentees-bounces@lists.linuxfoundation.org Sender: "Linux-kernel-mentees" Currently, direct copies of drm_file->master pointers should be protected by drm_device.master_mutex when being dereferenced. This is because drm_file->master is not invariant for the lifetime of drm_file. If drm_file is not the creator of master, then drm_file->is_master is false, and a call to drm_setmaster_ioctl will invoke drm_new_set_master, which then allocates a new master for drm_file and puts the old master. Thus, without holding drm_device.master_mutex, the old value of drm_file->master could be freed while it is being used by another concurrent process. In drm_lease.c, there are multiple instances where drm_file->master is accessed and dereferenced while drm_device.master_mutex is not held. This makes drm_lease.c vulnerable to use-after-free bugs. We address this issue in 3 ways: 1. Clarify in the kerneldoc that drm_file->master is protected by drm_device.master_mutex. 2. Add a new drm_file_get_master() function that calls drm_master_get on drm_file->master while holding on to drm_device.master_mutex. Since drm_master_get increments the reference count of master, this prevents master from being freed until we unreference it with drm_master_put. 3. In each case where drm_file->master is directly accessed and eventually dereferenced in drm_lease.c, we wrap the access in a call to the new drm_file_get_master function, then unreference the master pointer once we are done using it. Reported-by: Daniel Vetter Signed-off-by: Desmond Cheong Zhi Xi --- drivers/gpu/drm/drm_auth.c | 25 ++++++++++++ drivers/gpu/drm/drm_lease.c | 77 +++++++++++++++++++++++++++---------- include/drm/drm_auth.h | 1 + include/drm/drm_file.h | 15 ++++++-- 4 files changed, 95 insertions(+), 23 deletions(-) diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c index ab1863c5a5a0..c36a0b72be26 100644 --- a/drivers/gpu/drm/drm_auth.c +++ b/drivers/gpu/drm/drm_auth.c @@ -384,6 +384,31 @@ struct drm_master *drm_master_get(struct drm_master *master) } EXPORT_SYMBOL(drm_master_get); +/** + * drm_file_get_master - reference &drm_file.master of @file_priv + * @file_priv: DRM file private + * + * Increments the reference count of @file_priv's &drm_file.master and returns + * the &drm_file.master. If @file_priv has no &drm_file.master, returns NULL. + * + * Master pointers returned from this function should be unreferenced using + * drm_master_put(). + */ +struct drm_master *drm_file_get_master(struct drm_file *file_priv) +{ + struct drm_master *master = NULL; + + mutex_lock(&file_priv->minor->dev->master_mutex); + if (!file_priv->master) + goto unlock; + master = drm_master_get(file_priv->master); + +unlock: + mutex_unlock(&file_priv->minor->dev->master_mutex); + return master; +} +EXPORT_SYMBOL(drm_file_get_master); + static void drm_master_destroy(struct kref *kref) { struct drm_master *master = container_of(kref, struct drm_master, refcount); diff --git a/drivers/gpu/drm/drm_lease.c b/drivers/gpu/drm/drm_lease.c index 00fb433bcef1..cdcc87fa9685 100644 --- a/drivers/gpu/drm/drm_lease.c +++ b/drivers/gpu/drm/drm_lease.c @@ -106,10 +106,19 @@ static bool _drm_has_leased(struct drm_master *master, int id) */ bool _drm_lease_held(struct drm_file *file_priv, int id) { - if (!file_priv || !file_priv->master) + bool ret; + struct drm_master *master; + + if (!file_priv) return true; - return _drm_lease_held_master(file_priv->master, id); + master = drm_file_get_master(file_priv); + if (master == NULL) + return true; + ret = _drm_lease_held_master(master, id); + drm_master_put(&master); + + return ret; } /** @@ -128,13 +137,20 @@ bool drm_lease_held(struct drm_file *file_priv, int id) struct drm_master *master; bool ret; - if (!file_priv || !file_priv->master || !file_priv->master->lessor) + if (!file_priv) return true; - master = file_priv->master; + master = drm_file_get_master(file_priv); + if (master == NULL) + return true; + if (!master->lessor) { + drm_master_put(&master); + return true; + } mutex_lock(&master->dev->mode_config.idr_mutex); ret = _drm_lease_held_master(master, id); mutex_unlock(&master->dev->mode_config.idr_mutex); + drm_master_put(&master); return ret; } @@ -154,10 +170,16 @@ uint32_t drm_lease_filter_crtcs(struct drm_file *file_priv, uint32_t crtcs_in) int count_in, count_out; uint32_t crtcs_out = 0; - if (!file_priv || !file_priv->master || !file_priv->master->lessor) + if (!file_priv) return crtcs_in; - master = file_priv->master; + master = drm_file_get_master(file_priv); + if (master == NULL) + return crtcs_in; + if (!master->lessor) { + drm_master_put(&master); + return crtcs_in; + } dev = master->dev; count_in = count_out = 0; @@ -176,6 +198,7 @@ uint32_t drm_lease_filter_crtcs(struct drm_file *file_priv, uint32_t crtcs_in) count_in++; } mutex_unlock(&master->dev->mode_config.idr_mutex); + drm_master_put(&master); return crtcs_out; } @@ -489,7 +512,7 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, size_t object_count; int ret = 0; struct idr leases; - struct drm_master *lessor = lessor_priv->master; + struct drm_master *lessor; struct drm_master *lessee = NULL; struct file *lessee_file = NULL; struct file *lessor_file = lessor_priv->filp; @@ -501,12 +524,6 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, if (!drm_core_check_feature(dev, DRIVER_MODESET)) return -EOPNOTSUPP; - /* Do not allow sub-leases */ - if (lessor->lessor) { - DRM_DEBUG_LEASE("recursive leasing not allowed\n"); - return -EINVAL; - } - /* need some objects */ if (cl->object_count == 0) { DRM_DEBUG_LEASE("no objects in lease\n"); @@ -518,12 +535,22 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, return -EINVAL; } + lessor = drm_file_get_master(lessor_priv); + /* Do not allow sub-leases */ + if (lessor->lessor) { + DRM_DEBUG_LEASE("recursive leasing not allowed\n"); + ret = -EINVAL; + goto out_lessor; + } + object_count = cl->object_count; object_ids = memdup_user(u64_to_user_ptr(cl->object_ids), array_size(object_count, sizeof(__u32))); - if (IS_ERR(object_ids)) - return PTR_ERR(object_ids); + if (IS_ERR(object_ids)) { + ret = PTR_ERR(object_ids); + goto out_lessor; + } idr_init(&leases); @@ -534,14 +561,15 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, if (ret) { DRM_DEBUG_LEASE("lease object lookup failed: %i\n", ret); idr_destroy(&leases); - return ret; + goto out_lessor; } /* Allocate a file descriptor for the lease */ fd = get_unused_fd_flags(cl->flags & (O_CLOEXEC | O_NONBLOCK)); if (fd < 0) { idr_destroy(&leases); - return fd; + ret = fd; + goto out_lessor; } DRM_DEBUG_LEASE("Creating lease\n"); @@ -577,6 +605,7 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, /* Hook up the fd */ fd_install(fd, lessee_file); + drm_master_put(&lessor); DRM_DEBUG_LEASE("drm_mode_create_lease_ioctl succeeded\n"); return 0; @@ -586,6 +615,8 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, out_leases: put_unused_fd(fd); +out_lessor: + drm_master_put(&lessor); DRM_DEBUG_LEASE("drm_mode_create_lease_ioctl failed: %d\n", ret); return ret; } @@ -608,7 +639,7 @@ int drm_mode_list_lessees_ioctl(struct drm_device *dev, struct drm_mode_list_lessees *arg = data; __u32 __user *lessee_ids = (__u32 __user *) (uintptr_t) (arg->lessees_ptr); __u32 count_lessees = arg->count_lessees; - struct drm_master *lessor = lessor_priv->master, *lessee; + struct drm_master *lessor, *lessee; int count; int ret = 0; @@ -619,6 +650,7 @@ int drm_mode_list_lessees_ioctl(struct drm_device *dev, if (!drm_core_check_feature(dev, DRIVER_MODESET)) return -EOPNOTSUPP; + lessor = drm_file_get_master(lessor_priv); DRM_DEBUG_LEASE("List lessees for %d\n", lessor->lessee_id); mutex_lock(&dev->mode_config.idr_mutex); @@ -642,6 +674,7 @@ int drm_mode_list_lessees_ioctl(struct drm_device *dev, arg->count_lessees = count; mutex_unlock(&dev->mode_config.idr_mutex); + drm_master_put(&lessor); return ret; } @@ -661,7 +694,7 @@ int drm_mode_get_lease_ioctl(struct drm_device *dev, struct drm_mode_get_lease *arg = data; __u32 __user *object_ids = (__u32 __user *) (uintptr_t) (arg->objects_ptr); __u32 count_objects = arg->count_objects; - struct drm_master *lessee = lessee_priv->master; + struct drm_master *lessee; struct idr *object_idr; int count; void *entry; @@ -675,6 +708,7 @@ int drm_mode_get_lease_ioctl(struct drm_device *dev, if (!drm_core_check_feature(dev, DRIVER_MODESET)) return -EOPNOTSUPP; + lessee = drm_file_get_master(lessee_priv); DRM_DEBUG_LEASE("get lease for %d\n", lessee->lessee_id); mutex_lock(&dev->mode_config.idr_mutex); @@ -702,6 +736,7 @@ int drm_mode_get_lease_ioctl(struct drm_device *dev, arg->count_objects = count; mutex_unlock(&dev->mode_config.idr_mutex); + drm_master_put(&lessee); return ret; } @@ -720,7 +755,7 @@ int drm_mode_revoke_lease_ioctl(struct drm_device *dev, void *data, struct drm_file *lessor_priv) { struct drm_mode_revoke_lease *arg = data; - struct drm_master *lessor = lessor_priv->master; + struct drm_master *lessor; struct drm_master *lessee; int ret = 0; @@ -730,6 +765,7 @@ int drm_mode_revoke_lease_ioctl(struct drm_device *dev, if (!drm_core_check_feature(dev, DRIVER_MODESET)) return -EOPNOTSUPP; + lessor = drm_file_get_master(lessor_priv); mutex_lock(&dev->mode_config.idr_mutex); lessee = _drm_find_lessee(lessor, arg->lessee_id); @@ -750,6 +786,7 @@ int drm_mode_revoke_lease_ioctl(struct drm_device *dev, fail: mutex_unlock(&dev->mode_config.idr_mutex); + drm_master_put(&lessor); return ret; } diff --git a/include/drm/drm_auth.h b/include/drm/drm_auth.h index 6bf8b2b78991..f99d3417f304 100644 --- a/include/drm/drm_auth.h +++ b/include/drm/drm_auth.h @@ -107,6 +107,7 @@ struct drm_master { }; struct drm_master *drm_master_get(struct drm_master *master); +struct drm_master *drm_file_get_master(struct drm_file *file_priv); void drm_master_put(struct drm_master **master); bool drm_is_current_master(struct drm_file *fpriv); diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h index b81b3bfb08c8..e9931fca4ab7 100644 --- a/include/drm/drm_file.h +++ b/include/drm/drm_file.h @@ -226,9 +226,18 @@ struct drm_file { /** * @master: * - * Master this node is currently associated with. Only relevant if - * drm_is_primary_client() returns true. Note that this only - * matches &drm_device.master if the master is the currently active one. + * Master this node is currently associated with. Protected by struct + * &drm_device.master_mutex. + * + * Only relevant if drm_is_primary_client() returns true. Note that + * this only matches &drm_device.master if the master is the currently + * active one. + * + * When obtaining a copy of this pointer, it is recommended to either + * hold struct &drm_device.master_mutex for the duration of the + * pointer's use, or to use drm_file_get_master() if struct + * &drm_device.master_mutex is not currently held and there is no other + * need to hold it. This prevents @master from being freed during use. * * See also @authentication and @is_master and the :ref:`section on * primary nodes and authentication `. -- 2.25.1 _______________________________________________ Linux-kernel-mentees mailing list Linux-kernel-mentees@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees 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=-13.5 required=3.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED,DKIM_INVALID,DKIM_SIGNED,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 00472C11F66 for ; Tue, 29 Jun 2021 03:38:17 +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 C08D061D3B for ; 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Mon, 28 Jun 2021 20:38:14 -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 Subject: [PATCH v5 3/3] drm: protect drm_master pointers in drm_lease.c Date: Tue, 29 Jun 2021 11:37:06 +0800 Message-Id: <20210629033706.20537-4-desmondcheongzx@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210629033706.20537-1-desmondcheongzx@gmail.com> References: <20210629033706.20537-1-desmondcheongzx@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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: , Cc: Daniel Vetter , gregkh@linuxfoundation.org, intel-gfx@lists.freedesktop.org, emil.l.velikov@gmail.com, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, skhan@linuxfoundation.org, Desmond Cheong Zhi Xi , linux-kernel-mentees@lists.linuxfoundation.org, linux-media@vger.kernel.org Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Currently, direct copies of drm_file->master pointers should be protected by drm_device.master_mutex when being dereferenced. This is because drm_file->master is not invariant for the lifetime of drm_file. If drm_file is not the creator of master, then drm_file->is_master is false, and a call to drm_setmaster_ioctl will invoke drm_new_set_master, which then allocates a new master for drm_file and puts the old master. Thus, without holding drm_device.master_mutex, the old value of drm_file->master could be freed while it is being used by another concurrent process. In drm_lease.c, there are multiple instances where drm_file->master is accessed and dereferenced while drm_device.master_mutex is not held. This makes drm_lease.c vulnerable to use-after-free bugs. We address this issue in 3 ways: 1. Clarify in the kerneldoc that drm_file->master is protected by drm_device.master_mutex. 2. Add a new drm_file_get_master() function that calls drm_master_get on drm_file->master while holding on to drm_device.master_mutex. Since drm_master_get increments the reference count of master, this prevents master from being freed until we unreference it with drm_master_put. 3. In each case where drm_file->master is directly accessed and eventually dereferenced in drm_lease.c, we wrap the access in a call to the new drm_file_get_master function, then unreference the master pointer once we are done using it. Reported-by: Daniel Vetter Signed-off-by: Desmond Cheong Zhi Xi --- drivers/gpu/drm/drm_auth.c | 25 ++++++++++++ drivers/gpu/drm/drm_lease.c | 77 +++++++++++++++++++++++++++---------- include/drm/drm_auth.h | 1 + include/drm/drm_file.h | 15 ++++++-- 4 files changed, 95 insertions(+), 23 deletions(-) diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c index ab1863c5a5a0..c36a0b72be26 100644 --- a/drivers/gpu/drm/drm_auth.c +++ b/drivers/gpu/drm/drm_auth.c @@ -384,6 +384,31 @@ struct drm_master *drm_master_get(struct drm_master *master) } EXPORT_SYMBOL(drm_master_get); +/** + * drm_file_get_master - reference &drm_file.master of @file_priv + * @file_priv: DRM file private + * + * Increments the reference count of @file_priv's &drm_file.master and returns + * the &drm_file.master. If @file_priv has no &drm_file.master, returns NULL. + * + * Master pointers returned from this function should be unreferenced using + * drm_master_put(). + */ +struct drm_master *drm_file_get_master(struct drm_file *file_priv) +{ + struct drm_master *master = NULL; + + mutex_lock(&file_priv->minor->dev->master_mutex); + if (!file_priv->master) + goto unlock; + master = drm_master_get(file_priv->master); + +unlock: + mutex_unlock(&file_priv->minor->dev->master_mutex); + return master; +} +EXPORT_SYMBOL(drm_file_get_master); + static void drm_master_destroy(struct kref *kref) { struct drm_master *master = container_of(kref, struct drm_master, refcount); diff --git a/drivers/gpu/drm/drm_lease.c b/drivers/gpu/drm/drm_lease.c index 00fb433bcef1..cdcc87fa9685 100644 --- a/drivers/gpu/drm/drm_lease.c +++ b/drivers/gpu/drm/drm_lease.c @@ -106,10 +106,19 @@ static bool _drm_has_leased(struct drm_master *master, int id) */ bool _drm_lease_held(struct drm_file *file_priv, int id) { - if (!file_priv || !file_priv->master) + bool ret; + struct drm_master *master; + + if (!file_priv) return true; - return _drm_lease_held_master(file_priv->master, id); + master = drm_file_get_master(file_priv); + if (master == NULL) + return true; + ret = _drm_lease_held_master(master, id); + drm_master_put(&master); + + return ret; } /** @@ -128,13 +137,20 @@ bool drm_lease_held(struct drm_file *file_priv, int id) struct drm_master *master; bool ret; - if (!file_priv || !file_priv->master || !file_priv->master->lessor) + if (!file_priv) return true; - master = file_priv->master; + master = drm_file_get_master(file_priv); + if (master == NULL) + return true; + if (!master->lessor) { + drm_master_put(&master); + return true; + } mutex_lock(&master->dev->mode_config.idr_mutex); ret = _drm_lease_held_master(master, id); mutex_unlock(&master->dev->mode_config.idr_mutex); + drm_master_put(&master); return ret; } @@ -154,10 +170,16 @@ uint32_t drm_lease_filter_crtcs(struct drm_file *file_priv, uint32_t crtcs_in) int count_in, count_out; uint32_t crtcs_out = 0; - if (!file_priv || !file_priv->master || !file_priv->master->lessor) + if (!file_priv) return crtcs_in; - master = file_priv->master; + master = drm_file_get_master(file_priv); + if (master == NULL) + return crtcs_in; + if (!master->lessor) { + drm_master_put(&master); + return crtcs_in; + } dev = master->dev; count_in = count_out = 0; @@ -176,6 +198,7 @@ uint32_t drm_lease_filter_crtcs(struct drm_file *file_priv, uint32_t crtcs_in) count_in++; } mutex_unlock(&master->dev->mode_config.idr_mutex); + drm_master_put(&master); return crtcs_out; } @@ -489,7 +512,7 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, size_t object_count; int ret = 0; struct idr leases; - struct drm_master *lessor = lessor_priv->master; + struct drm_master *lessor; struct drm_master *lessee = NULL; struct file *lessee_file = NULL; struct file *lessor_file = lessor_priv->filp; @@ -501,12 +524,6 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, if (!drm_core_check_feature(dev, DRIVER_MODESET)) return -EOPNOTSUPP; - /* Do not allow sub-leases */ - if (lessor->lessor) { - DRM_DEBUG_LEASE("recursive leasing not allowed\n"); - return -EINVAL; - } - /* need some objects */ if (cl->object_count == 0) { DRM_DEBUG_LEASE("no objects in lease\n"); @@ -518,12 +535,22 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, return -EINVAL; } + lessor = drm_file_get_master(lessor_priv); + /* Do not allow sub-leases */ + if (lessor->lessor) { + DRM_DEBUG_LEASE("recursive leasing not allowed\n"); + ret = -EINVAL; + goto out_lessor; + } + object_count = cl->object_count; object_ids = memdup_user(u64_to_user_ptr(cl->object_ids), array_size(object_count, sizeof(__u32))); - if (IS_ERR(object_ids)) - return PTR_ERR(object_ids); + if (IS_ERR(object_ids)) { + ret = PTR_ERR(object_ids); + goto out_lessor; + } idr_init(&leases); @@ -534,14 +561,15 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, if (ret) { DRM_DEBUG_LEASE("lease object lookup failed: %i\n", ret); idr_destroy(&leases); - return ret; + goto out_lessor; } /* Allocate a file descriptor for the lease */ fd = get_unused_fd_flags(cl->flags & (O_CLOEXEC | O_NONBLOCK)); if (fd < 0) { idr_destroy(&leases); - return fd; + ret = fd; + goto out_lessor; } DRM_DEBUG_LEASE("Creating lease\n"); @@ -577,6 +605,7 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, /* Hook up the fd */ fd_install(fd, lessee_file); + drm_master_put(&lessor); DRM_DEBUG_LEASE("drm_mode_create_lease_ioctl succeeded\n"); return 0; @@ -586,6 +615,8 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, out_leases: put_unused_fd(fd); +out_lessor: + drm_master_put(&lessor); DRM_DEBUG_LEASE("drm_mode_create_lease_ioctl failed: %d\n", ret); return ret; } @@ -608,7 +639,7 @@ int drm_mode_list_lessees_ioctl(struct drm_device *dev, struct drm_mode_list_lessees *arg = data; __u32 __user *lessee_ids = (__u32 __user *) (uintptr_t) (arg->lessees_ptr); __u32 count_lessees = arg->count_lessees; - struct drm_master *lessor = lessor_priv->master, *lessee; + struct drm_master *lessor, *lessee; int count; int ret = 0; @@ -619,6 +650,7 @@ int drm_mode_list_lessees_ioctl(struct drm_device *dev, if (!drm_core_check_feature(dev, DRIVER_MODESET)) return -EOPNOTSUPP; + lessor = drm_file_get_master(lessor_priv); DRM_DEBUG_LEASE("List lessees for %d\n", lessor->lessee_id); mutex_lock(&dev->mode_config.idr_mutex); @@ -642,6 +674,7 @@ int drm_mode_list_lessees_ioctl(struct drm_device *dev, arg->count_lessees = count; mutex_unlock(&dev->mode_config.idr_mutex); + drm_master_put(&lessor); return ret; } @@ -661,7 +694,7 @@ int drm_mode_get_lease_ioctl(struct drm_device *dev, struct drm_mode_get_lease *arg = data; __u32 __user *object_ids = (__u32 __user *) (uintptr_t) (arg->objects_ptr); __u32 count_objects = arg->count_objects; - struct drm_master *lessee = lessee_priv->master; + struct drm_master *lessee; struct idr *object_idr; int count; void *entry; @@ -675,6 +708,7 @@ int drm_mode_get_lease_ioctl(struct drm_device *dev, if (!drm_core_check_feature(dev, DRIVER_MODESET)) return -EOPNOTSUPP; + lessee = drm_file_get_master(lessee_priv); DRM_DEBUG_LEASE("get lease for %d\n", lessee->lessee_id); mutex_lock(&dev->mode_config.idr_mutex); @@ -702,6 +736,7 @@ int drm_mode_get_lease_ioctl(struct drm_device *dev, arg->count_objects = count; mutex_unlock(&dev->mode_config.idr_mutex); + drm_master_put(&lessee); return ret; } @@ -720,7 +755,7 @@ int drm_mode_revoke_lease_ioctl(struct drm_device *dev, void *data, struct drm_file *lessor_priv) { struct drm_mode_revoke_lease *arg = data; - struct drm_master *lessor = lessor_priv->master; + struct drm_master *lessor; struct drm_master *lessee; int ret = 0; @@ -730,6 +765,7 @@ int drm_mode_revoke_lease_ioctl(struct drm_device *dev, if (!drm_core_check_feature(dev, DRIVER_MODESET)) return -EOPNOTSUPP; + lessor = drm_file_get_master(lessor_priv); mutex_lock(&dev->mode_config.idr_mutex); lessee = _drm_find_lessee(lessor, arg->lessee_id); @@ -750,6 +786,7 @@ int drm_mode_revoke_lease_ioctl(struct drm_device *dev, fail: mutex_unlock(&dev->mode_config.idr_mutex); + drm_master_put(&lessor); return ret; } diff --git a/include/drm/drm_auth.h b/include/drm/drm_auth.h index 6bf8b2b78991..f99d3417f304 100644 --- a/include/drm/drm_auth.h +++ b/include/drm/drm_auth.h @@ -107,6 +107,7 @@ struct drm_master { }; struct drm_master *drm_master_get(struct drm_master *master); +struct drm_master *drm_file_get_master(struct drm_file *file_priv); void drm_master_put(struct drm_master **master); bool drm_is_current_master(struct drm_file *fpriv); diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h index b81b3bfb08c8..e9931fca4ab7 100644 --- a/include/drm/drm_file.h +++ b/include/drm/drm_file.h @@ -226,9 +226,18 @@ struct drm_file { /** * @master: * - * Master this node is currently associated with. Only relevant if - * drm_is_primary_client() returns true. Note that this only - * matches &drm_device.master if the master is the currently active one. + * Master this node is currently associated with. Protected by struct + * &drm_device.master_mutex. + * + * Only relevant if drm_is_primary_client() returns true. Note that + * this only matches &drm_device.master if the master is the currently + * active one. + * + * When obtaining a copy of this pointer, it is recommended to either + * hold struct &drm_device.master_mutex for the duration of the + * pointer's use, or to use drm_file_get_master() if struct + * &drm_device.master_mutex is not currently held and there is no other + * need to hold it. This prevents @master from being freed during use. * * See also @authentication and @is_master and the :ref:`section on * primary nodes and authentication `. -- 2.25.1 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=-13.6 required=3.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED,DKIM_INVALID,DKIM_SIGNED,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 3B9E0C11F67 for ; Tue, 29 Jun 2021 14:26:34 +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 09C9C61DC0 for ; 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Mon, 28 Jun 2021 20:38:14 -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 Date: Tue, 29 Jun 2021 11:37:06 +0800 Message-Id: <20210629033706.20537-4-desmondcheongzx@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210629033706.20537-1-desmondcheongzx@gmail.com> References: <20210629033706.20537-1-desmondcheongzx@gmail.com> MIME-Version: 1.0 X-Mailman-Approved-At: Tue, 29 Jun 2021 14:26:26 +0000 Subject: [Intel-gfx] [PATCH v5 3/3] drm: protect drm_master pointers in drm_lease.c X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Daniel Vetter , gregkh@linuxfoundation.org, intel-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, skhan@linuxfoundation.org, Desmond Cheong Zhi Xi , linux-kernel-mentees@lists.linuxfoundation.org, linux-media@vger.kernel.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" Currently, direct copies of drm_file->master pointers should be protected by drm_device.master_mutex when being dereferenced. This is because drm_file->master is not invariant for the lifetime of drm_file. If drm_file is not the creator of master, then drm_file->is_master is false, and a call to drm_setmaster_ioctl will invoke drm_new_set_master, which then allocates a new master for drm_file and puts the old master. Thus, without holding drm_device.master_mutex, the old value of drm_file->master could be freed while it is being used by another concurrent process. In drm_lease.c, there are multiple instances where drm_file->master is accessed and dereferenced while drm_device.master_mutex is not held. This makes drm_lease.c vulnerable to use-after-free bugs. We address this issue in 3 ways: 1. Clarify in the kerneldoc that drm_file->master is protected by drm_device.master_mutex. 2. Add a new drm_file_get_master() function that calls drm_master_get on drm_file->master while holding on to drm_device.master_mutex. Since drm_master_get increments the reference count of master, this prevents master from being freed until we unreference it with drm_master_put. 3. In each case where drm_file->master is directly accessed and eventually dereferenced in drm_lease.c, we wrap the access in a call to the new drm_file_get_master function, then unreference the master pointer once we are done using it. Reported-by: Daniel Vetter Signed-off-by: Desmond Cheong Zhi Xi --- drivers/gpu/drm/drm_auth.c | 25 ++++++++++++ drivers/gpu/drm/drm_lease.c | 77 +++++++++++++++++++++++++++---------- include/drm/drm_auth.h | 1 + include/drm/drm_file.h | 15 ++++++-- 4 files changed, 95 insertions(+), 23 deletions(-) diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c index ab1863c5a5a0..c36a0b72be26 100644 --- a/drivers/gpu/drm/drm_auth.c +++ b/drivers/gpu/drm/drm_auth.c @@ -384,6 +384,31 @@ struct drm_master *drm_master_get(struct drm_master *master) } EXPORT_SYMBOL(drm_master_get); +/** + * drm_file_get_master - reference &drm_file.master of @file_priv + * @file_priv: DRM file private + * + * Increments the reference count of @file_priv's &drm_file.master and returns + * the &drm_file.master. If @file_priv has no &drm_file.master, returns NULL. + * + * Master pointers returned from this function should be unreferenced using + * drm_master_put(). + */ +struct drm_master *drm_file_get_master(struct drm_file *file_priv) +{ + struct drm_master *master = NULL; + + mutex_lock(&file_priv->minor->dev->master_mutex); + if (!file_priv->master) + goto unlock; + master = drm_master_get(file_priv->master); + +unlock: + mutex_unlock(&file_priv->minor->dev->master_mutex); + return master; +} +EXPORT_SYMBOL(drm_file_get_master); + static void drm_master_destroy(struct kref *kref) { struct drm_master *master = container_of(kref, struct drm_master, refcount); diff --git a/drivers/gpu/drm/drm_lease.c b/drivers/gpu/drm/drm_lease.c index 00fb433bcef1..cdcc87fa9685 100644 --- a/drivers/gpu/drm/drm_lease.c +++ b/drivers/gpu/drm/drm_lease.c @@ -106,10 +106,19 @@ static bool _drm_has_leased(struct drm_master *master, int id) */ bool _drm_lease_held(struct drm_file *file_priv, int id) { - if (!file_priv || !file_priv->master) + bool ret; + struct drm_master *master; + + if (!file_priv) return true; - return _drm_lease_held_master(file_priv->master, id); + master = drm_file_get_master(file_priv); + if (master == NULL) + return true; + ret = _drm_lease_held_master(master, id); + drm_master_put(&master); + + return ret; } /** @@ -128,13 +137,20 @@ bool drm_lease_held(struct drm_file *file_priv, int id) struct drm_master *master; bool ret; - if (!file_priv || !file_priv->master || !file_priv->master->lessor) + if (!file_priv) return true; - master = file_priv->master; + master = drm_file_get_master(file_priv); + if (master == NULL) + return true; + if (!master->lessor) { + drm_master_put(&master); + return true; + } mutex_lock(&master->dev->mode_config.idr_mutex); ret = _drm_lease_held_master(master, id); mutex_unlock(&master->dev->mode_config.idr_mutex); + drm_master_put(&master); return ret; } @@ -154,10 +170,16 @@ uint32_t drm_lease_filter_crtcs(struct drm_file *file_priv, uint32_t crtcs_in) int count_in, count_out; uint32_t crtcs_out = 0; - if (!file_priv || !file_priv->master || !file_priv->master->lessor) + if (!file_priv) return crtcs_in; - master = file_priv->master; + master = drm_file_get_master(file_priv); + if (master == NULL) + return crtcs_in; + if (!master->lessor) { + drm_master_put(&master); + return crtcs_in; + } dev = master->dev; count_in = count_out = 0; @@ -176,6 +198,7 @@ uint32_t drm_lease_filter_crtcs(struct drm_file *file_priv, uint32_t crtcs_in) count_in++; } mutex_unlock(&master->dev->mode_config.idr_mutex); + drm_master_put(&master); return crtcs_out; } @@ -489,7 +512,7 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, size_t object_count; int ret = 0; struct idr leases; - struct drm_master *lessor = lessor_priv->master; + struct drm_master *lessor; struct drm_master *lessee = NULL; struct file *lessee_file = NULL; struct file *lessor_file = lessor_priv->filp; @@ -501,12 +524,6 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, if (!drm_core_check_feature(dev, DRIVER_MODESET)) return -EOPNOTSUPP; - /* Do not allow sub-leases */ - if (lessor->lessor) { - DRM_DEBUG_LEASE("recursive leasing not allowed\n"); - return -EINVAL; - } - /* need some objects */ if (cl->object_count == 0) { DRM_DEBUG_LEASE("no objects in lease\n"); @@ -518,12 +535,22 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, return -EINVAL; } + lessor = drm_file_get_master(lessor_priv); + /* Do not allow sub-leases */ + if (lessor->lessor) { + DRM_DEBUG_LEASE("recursive leasing not allowed\n"); + ret = -EINVAL; + goto out_lessor; + } + object_count = cl->object_count; object_ids = memdup_user(u64_to_user_ptr(cl->object_ids), array_size(object_count, sizeof(__u32))); - if (IS_ERR(object_ids)) - return PTR_ERR(object_ids); + if (IS_ERR(object_ids)) { + ret = PTR_ERR(object_ids); + goto out_lessor; + } idr_init(&leases); @@ -534,14 +561,15 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, if (ret) { DRM_DEBUG_LEASE("lease object lookup failed: %i\n", ret); idr_destroy(&leases); - return ret; + goto out_lessor; } /* Allocate a file descriptor for the lease */ fd = get_unused_fd_flags(cl->flags & (O_CLOEXEC | O_NONBLOCK)); if (fd < 0) { idr_destroy(&leases); - return fd; + ret = fd; + goto out_lessor; } DRM_DEBUG_LEASE("Creating lease\n"); @@ -577,6 +605,7 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, /* Hook up the fd */ fd_install(fd, lessee_file); + drm_master_put(&lessor); DRM_DEBUG_LEASE("drm_mode_create_lease_ioctl succeeded\n"); return 0; @@ -586,6 +615,8 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, out_leases: put_unused_fd(fd); +out_lessor: + drm_master_put(&lessor); DRM_DEBUG_LEASE("drm_mode_create_lease_ioctl failed: %d\n", ret); return ret; } @@ -608,7 +639,7 @@ int drm_mode_list_lessees_ioctl(struct drm_device *dev, struct drm_mode_list_lessees *arg = data; __u32 __user *lessee_ids = (__u32 __user *) (uintptr_t) (arg->lessees_ptr); __u32 count_lessees = arg->count_lessees; - struct drm_master *lessor = lessor_priv->master, *lessee; + struct drm_master *lessor, *lessee; int count; int ret = 0; @@ -619,6 +650,7 @@ int drm_mode_list_lessees_ioctl(struct drm_device *dev, if (!drm_core_check_feature(dev, DRIVER_MODESET)) return -EOPNOTSUPP; + lessor = drm_file_get_master(lessor_priv); DRM_DEBUG_LEASE("List lessees for %d\n", lessor->lessee_id); mutex_lock(&dev->mode_config.idr_mutex); @@ -642,6 +674,7 @@ int drm_mode_list_lessees_ioctl(struct drm_device *dev, arg->count_lessees = count; mutex_unlock(&dev->mode_config.idr_mutex); + drm_master_put(&lessor); return ret; } @@ -661,7 +694,7 @@ int drm_mode_get_lease_ioctl(struct drm_device *dev, struct drm_mode_get_lease *arg = data; __u32 __user *object_ids = (__u32 __user *) (uintptr_t) (arg->objects_ptr); __u32 count_objects = arg->count_objects; - struct drm_master *lessee = lessee_priv->master; + struct drm_master *lessee; struct idr *object_idr; int count; void *entry; @@ -675,6 +708,7 @@ int drm_mode_get_lease_ioctl(struct drm_device *dev, if (!drm_core_check_feature(dev, DRIVER_MODESET)) return -EOPNOTSUPP; + lessee = drm_file_get_master(lessee_priv); DRM_DEBUG_LEASE("get lease for %d\n", lessee->lessee_id); mutex_lock(&dev->mode_config.idr_mutex); @@ -702,6 +736,7 @@ int drm_mode_get_lease_ioctl(struct drm_device *dev, arg->count_objects = count; mutex_unlock(&dev->mode_config.idr_mutex); + drm_master_put(&lessee); return ret; } @@ -720,7 +755,7 @@ int drm_mode_revoke_lease_ioctl(struct drm_device *dev, void *data, struct drm_file *lessor_priv) { struct drm_mode_revoke_lease *arg = data; - struct drm_master *lessor = lessor_priv->master; + struct drm_master *lessor; struct drm_master *lessee; int ret = 0; @@ -730,6 +765,7 @@ int drm_mode_revoke_lease_ioctl(struct drm_device *dev, if (!drm_core_check_feature(dev, DRIVER_MODESET)) return -EOPNOTSUPP; + lessor = drm_file_get_master(lessor_priv); mutex_lock(&dev->mode_config.idr_mutex); lessee = _drm_find_lessee(lessor, arg->lessee_id); @@ -750,6 +786,7 @@ int drm_mode_revoke_lease_ioctl(struct drm_device *dev, fail: mutex_unlock(&dev->mode_config.idr_mutex); + drm_master_put(&lessor); return ret; } diff --git a/include/drm/drm_auth.h b/include/drm/drm_auth.h index 6bf8b2b78991..f99d3417f304 100644 --- a/include/drm/drm_auth.h +++ b/include/drm/drm_auth.h @@ -107,6 +107,7 @@ struct drm_master { }; struct drm_master *drm_master_get(struct drm_master *master); +struct drm_master *drm_file_get_master(struct drm_file *file_priv); void drm_master_put(struct drm_master **master); bool drm_is_current_master(struct drm_file *fpriv); diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h index b81b3bfb08c8..e9931fca4ab7 100644 --- a/include/drm/drm_file.h +++ b/include/drm/drm_file.h @@ -226,9 +226,18 @@ struct drm_file { /** * @master: * - * Master this node is currently associated with. Only relevant if - * drm_is_primary_client() returns true. Note that this only - * matches &drm_device.master if the master is the currently active one. + * Master this node is currently associated with. Protected by struct + * &drm_device.master_mutex. + * + * Only relevant if drm_is_primary_client() returns true. Note that + * this only matches &drm_device.master if the master is the currently + * active one. + * + * When obtaining a copy of this pointer, it is recommended to either + * hold struct &drm_device.master_mutex for the duration of the + * pointer's use, or to use drm_file_get_master() if struct + * &drm_device.master_mutex is not currently held and there is no other + * need to hold it. This prevents @master from being freed during use. * * See also @authentication and @is_master and the :ref:`section on * primary nodes and authentication `. -- 2.25.1 _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx