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Hence, convert master_mutex into a rwsem to enable concurrent readers. Signed-off-by: Desmond Cheong Zhi Xi --- drivers/gpu/drm/drm_auth.c | 35 ++++++++++++++++++----------------- drivers/gpu/drm/drm_debugfs.c | 4 ++-- drivers/gpu/drm/drm_drv.c | 3 +-- drivers/gpu/drm/drm_ioctl.c | 10 +++++----- include/drm/drm_auth.h | 6 +++--- include/drm/drm_device.h | 10 ++++++---- include/drm/drm_file.h | 12 ++++++------ 7 files changed, 41 insertions(+), 39 deletions(-) diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c index 60a6b21474b1..73ade0513ccb 100644 --- a/drivers/gpu/drm/drm_auth.c +++ b/drivers/gpu/drm/drm_auth.c @@ -64,7 +64,7 @@ static bool drm_is_current_master_locked(struct drm_file *fpriv) { lockdep_assert_once(lockdep_is_held(&fpriv->master_lookup_lock) || - lockdep_is_held(&fpriv->minor->dev->master_mutex)); + lockdep_is_held(&fpriv->minor->dev->master_rwsem)); return fpriv->is_master && drm_lease_owner(fpriv->master) == fpriv->minor->dev->master; } @@ -96,7 +96,7 @@ int drm_getmagic(struct drm_device *dev, void *data, struct drm_file *file_priv) struct drm_auth *auth = data; int ret = 0; - mutex_lock(&dev->master_mutex); + down_write(&dev->master_rwsem); if (!file_priv->magic) { ret = idr_alloc(&file_priv->master->magic_map, file_priv, 1, 0, GFP_KERNEL); @@ -104,7 +104,7 @@ int drm_getmagic(struct drm_device *dev, void *data, struct drm_file *file_priv) file_priv->magic = ret; } auth->magic = file_priv->magic; - mutex_unlock(&dev->master_mutex); + up_write(&dev->master_rwsem); DRM_DEBUG("%u\n", auth->magic); @@ -119,13 +119,13 @@ int drm_authmagic(struct drm_device *dev, void *data, DRM_DEBUG("%u\n", auth->magic); - mutex_lock(&dev->master_mutex); + down_write(&dev->master_rwsem); file = idr_find(&file_priv->master->magic_map, auth->magic); if (file) { file->authenticated = 1; idr_replace(&file_priv->master->magic_map, NULL, auth->magic); } - mutex_unlock(&dev->master_mutex); + up_write(&dev->master_rwsem); return file ? 0 : -EINVAL; } @@ -167,7 +167,7 @@ static int drm_new_set_master(struct drm_device *dev, struct drm_file *fpriv) struct drm_master *old_master; struct drm_master *new_master; - lockdep_assert_held_once(&dev->master_mutex); + lockdep_assert_held_once(&dev->master_rwsem); WARN_ON(fpriv->is_master); old_master = fpriv->master; @@ -249,7 +249,7 @@ int drm_setmaster_ioctl(struct drm_device *dev, void *data, { int ret; - mutex_lock(&dev->master_mutex); + down_write(&dev->master_rwsem); ret = drm_master_check_perm(dev, file_priv); if (ret) @@ -281,7 +281,7 @@ int drm_setmaster_ioctl(struct drm_device *dev, void *data, drm_set_master(dev, file_priv, false); out_unlock: - mutex_unlock(&dev->master_mutex); + up_write(&dev->master_rwsem); return ret; } @@ -298,7 +298,7 @@ int drm_dropmaster_ioctl(struct drm_device *dev, void *data, { int ret; - mutex_lock(&dev->master_mutex); + down_write(&dev->master_rwsem); ret = drm_master_check_perm(dev, file_priv); if (ret) @@ -321,8 +321,9 @@ int drm_dropmaster_ioctl(struct drm_device *dev, void *data, } drm_drop_master(dev, file_priv); + out_unlock: - mutex_unlock(&dev->master_mutex); + up_write(&dev->master_rwsem); return ret; } @@ -334,7 +335,7 @@ int drm_master_open(struct drm_file *file_priv) /* if there is no current master make this fd it, but do not create * any master object for render clients */ - mutex_lock(&dev->master_mutex); + down_write(&dev->master_rwsem); if (!dev->master) { ret = drm_new_set_master(dev, file_priv); } else { @@ -342,7 +343,7 @@ int drm_master_open(struct drm_file *file_priv) file_priv->master = drm_master_get(dev->master); spin_unlock(&file_priv->master_lookup_lock); } - mutex_unlock(&dev->master_mutex); + up_write(&dev->master_rwsem); return ret; } @@ -352,7 +353,7 @@ void drm_master_release(struct drm_file *file_priv) struct drm_device *dev = file_priv->minor->dev; struct drm_master *master; - mutex_lock(&dev->master_mutex); + down_write(&dev->master_rwsem); master = file_priv->master; if (file_priv->magic) idr_remove(&file_priv->master->magic_map, file_priv->magic); @@ -375,7 +376,7 @@ void drm_master_release(struct drm_file *file_priv) /* drop the master reference held by the file priv */ if (file_priv->master) drm_master_put(&file_priv->master); - mutex_unlock(&dev->master_mutex); + up_write(&dev->master_rwsem); } /** @@ -450,9 +451,9 @@ EXPORT_SYMBOL(drm_master_put); /* Used by drm_client and drm_fb_helper */ bool drm_master_internal_acquire(struct drm_device *dev) { - mutex_lock(&dev->master_mutex); + down_read(&dev->master_rwsem); if (dev->master) { - mutex_unlock(&dev->master_mutex); + up_read(&dev->master_rwsem); return false; } @@ -463,6 +464,6 @@ EXPORT_SYMBOL(drm_master_internal_acquire); /* Used by drm_client and drm_fb_helper */ void drm_master_internal_release(struct drm_device *dev) { - mutex_unlock(&dev->master_mutex); + up_read(&dev->master_rwsem); } EXPORT_SYMBOL(drm_master_internal_release); diff --git a/drivers/gpu/drm/drm_debugfs.c b/drivers/gpu/drm/drm_debugfs.c index b0a826489488..b34c9c263188 100644 --- a/drivers/gpu/drm/drm_debugfs.c +++ b/drivers/gpu/drm/drm_debugfs.c @@ -55,7 +55,7 @@ static int drm_name_info(struct seq_file *m, void *data) struct drm_device *dev = minor->dev; struct drm_master *master; - mutex_lock(&dev->master_mutex); + down_read(&dev->master_rwsem); master = dev->master; seq_printf(m, "%s", dev->driver->name); if (dev->dev) @@ -65,7 +65,7 @@ static int drm_name_info(struct seq_file *m, void *data) if (dev->unique) seq_printf(m, " unique=%s", dev->unique); seq_printf(m, "\n"); - mutex_unlock(&dev->master_mutex); + up_read(&dev->master_rwsem); return 0; } diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c index 7a5097467ba5..4556bf42954c 100644 --- a/drivers/gpu/drm/drm_drv.c +++ b/drivers/gpu/drm/drm_drv.c @@ -570,7 +570,6 @@ static void drm_dev_init_release(struct drm_device *dev, void *res) /* Prevent use-after-free in drm_managed_release when debugging is * enabled. Slightly awkward, but can't really be helped. */ dev->dev = NULL; - mutex_destroy(&dev->master_mutex); mutex_destroy(&dev->clientlist_mutex); mutex_destroy(&dev->filelist_mutex); mutex_destroy(&dev->struct_mutex); @@ -611,7 +610,7 @@ static int drm_dev_init(struct drm_device *dev, mutex_init(&dev->struct_mutex); mutex_init(&dev->filelist_mutex); mutex_init(&dev->clientlist_mutex); - mutex_init(&dev->master_mutex); + init_rwsem(&dev->master_rwsem); ret = drmm_add_action(dev, drm_dev_init_release, NULL); if (ret) diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c index 26f3a9ede8fe..d25713b09b80 100644 --- a/drivers/gpu/drm/drm_ioctl.c +++ b/drivers/gpu/drm/drm_ioctl.c @@ -119,16 +119,16 @@ int drm_getunique(struct drm_device *dev, void *data, struct drm_unique *u = data; struct drm_master *master; - mutex_lock(&dev->master_mutex); + down_read(&dev->master_rwsem); master = file_priv->master; if (u->unique_len >= master->unique_len) { if (copy_to_user(u->unique, master->unique, master->unique_len)) { - mutex_unlock(&dev->master_mutex); + up_read(&dev->master_rwsem); return -EFAULT; } } u->unique_len = master->unique_len; - mutex_unlock(&dev->master_mutex); + up_read(&dev->master_rwsem); return 0; } @@ -385,7 +385,7 @@ static int drm_setversion(struct drm_device *dev, void *data, struct drm_file *f struct drm_set_version *sv = data; int if_version, retcode = 0; - mutex_lock(&dev->master_mutex); + down_write(&dev->master_rwsem); if (sv->drm_di_major != -1) { if (sv->drm_di_major != DRM_IF_MAJOR || sv->drm_di_minor < 0 || sv->drm_di_minor > DRM_IF_MINOR) { @@ -420,7 +420,7 @@ static int drm_setversion(struct drm_device *dev, void *data, struct drm_file *f sv->drm_di_minor = DRM_IF_MINOR; sv->drm_dd_major = dev->driver->major; sv->drm_dd_minor = dev->driver->minor; - mutex_unlock(&dev->master_mutex); + up_write(&dev->master_rwsem); return retcode; } diff --git a/include/drm/drm_auth.h b/include/drm/drm_auth.h index ba248ca8866f..f0a89e5fcaad 100644 --- a/include/drm/drm_auth.h +++ b/include/drm/drm_auth.h @@ -67,17 +67,17 @@ struct drm_master { struct drm_device *dev; /** * @unique: Unique identifier: e.g. busid. Protected by - * &drm_device.master_mutex. + * &drm_device.master_rwsem. */ char *unique; /** * @unique_len: Length of unique field. Protected by - * &drm_device.master_mutex. + * &drm_device.master_rwsem. */ int unique_len; /** * @magic_map: Map of used authentication tokens. Protected by - * &drm_device.master_mutex. + * &drm_device.master_rwsem. */ struct idr magic_map; void *driver_priv; diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h index 604b1d1b2d72..142fb2f6e74d 100644 --- a/include/drm/drm_device.h +++ b/include/drm/drm_device.h @@ -107,7 +107,7 @@ struct drm_device { * @master: * * Currently active master for this device. - * Protected by &master_mutex + * Protected by &master_rwsem */ struct drm_master *master; @@ -146,11 +146,13 @@ struct drm_device { struct mutex struct_mutex; /** - * @master_mutex: + * @master_rwsem: * - * Lock for &drm_minor.master and &drm_file.is_master + * Lock for &drm_device.master, &drm_file.was_master, + * &drm_file.is_master, &drm_file.master, &drm_master.unique, + * &drm_master.unique_len, and &drm_master.magic_map. */ - struct mutex master_mutex; + struct rw_semaphore master_rwsem; /** * @open_count: diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h index a3acb7ac3550..d12bb2ba7814 100644 --- a/include/drm/drm_file.h +++ b/include/drm/drm_file.h @@ -205,7 +205,7 @@ struct drm_file { * @was_master: * * This client has or had, master capability. Protected by struct - * &drm_device.master_mutex. + * &drm_device.master_rwsem. * * This is used to ensure that CAP_SYS_ADMIN is not enforced, if the * client is or was master in the past. @@ -216,7 +216,7 @@ struct drm_file { * @is_master: * * This client is the creator of @master. Protected by struct - * &drm_device.master_mutex. + * &drm_device.master_rwsem. * * See also the :ref:`section on primary nodes and authentication * `. @@ -227,19 +227,19 @@ struct drm_file { * @master: * * Master this node is currently associated with. Protected by struct - * &drm_device.master_mutex, and serialized by @master_lookup_lock. + * &drm_device.master_rwsem, and serialized by @master_lookup_lock. * * 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. * - * To update @master, both &drm_device.master_mutex and + * To update @master, both &drm_device.master_rwsem and * @master_lookup_lock need to be held, therefore holding either of * them is safe and enough for the read side. * * When dereferencing this pointer, either hold struct - * &drm_device.master_mutex for the duration of the pointer's use, or - * use drm_file_get_master() if struct &drm_device.master_mutex is not + * &drm_device.master_rwsem for the duration of the pointer's use, or + * use drm_file_get_master() if struct &drm_device.master_rwsem is not * currently held and there is no other need to hold it. This prevents * @master from being freed during use. * From patchwork Mon Aug 23 17:14:35 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: 501665 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 D0D49C4338F for ; Mon, 23 Aug 2021 17:15:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B777D6140F for ; Mon, 23 Aug 2021 17:15:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231772AbhHWRQT (ORCPT ); Mon, 23 Aug 2021 13:16:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40524 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231686AbhHWRQS (ORCPT ); Mon, 23 Aug 2021 13:16:18 -0400 Received: from mail-pl1-x62c.google.com (mail-pl1-x62c.google.com [IPv6:2607:f8b0:4864:20::62c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 16466C061575; Mon, 23 Aug 2021 10:15:36 -0700 (PDT) Received: by mail-pl1-x62c.google.com with SMTP id b9so6174655plx.2; Mon, 23 Aug 2021 10:15:36 -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=rtuBBmsJ+FZGp2Lavog/mblfNKKX32jG6r2O7uMrLj0=; b=e7uGGTmhO+HW1Nizy73RZhNXpoJcMOyUBRatHDEtcSEbl4wH5flpNGeotwgb4sFZ1d uLh0hZ5tWOj48C1zoLlCLjUBSGCxC0fS7N91OOvc4fa1fkOEqECuXy5ZAnOWmIq6Yqj9 TwxQsOiN9kxnU0IEKnl1qG9/dvDdoGonR3D8o4jyPv6SG66Bfe3OviRM3A70aDuwtiqp KEO5ddg5hkcLV0iDjLO7Y+hAU2UhgzsVSTI8WMd1Vka5+HuS61n7TojMfImVSpwkVJtP k8KXyWyaVcLlsT+B7mNKDUfoyOxOadvUD1DDrvpMrMMLvQfbk/XB+AOU+BB0C5G8FAEs ZerQ== 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=rtuBBmsJ+FZGp2Lavog/mblfNKKX32jG6r2O7uMrLj0=; b=k4yEEsghdX35cUiWsd2JB0CIYmB8hEd24qDB77L4Ft1CtPzHtKcCO31nGM7jVDChrw jszenUFsfSwXDZVu2lhCntLWKBxl9axG5bw1FqKkHbnyJjbsUGs2tPuDD+p3i1EIjTlY RCya1PQHRHQu/6lx8d3YiA8AFRN02hRzLFE3xz6dd5Q4mKw7/QZAEsV99zeP6c8sBHMo cnuk86bJXsq8QBXHhhLREFg5Gq/X6wPcxlyi/Hq9oAiDl+717BSU3MWANIgZ+MEqT0LS a9Jx6WsEuIs8I7MyyS+AZ0U3KytQ5d7mjQiA+0zWSV0yhMVLuC42tlM2Vf5Jh9cUZK2S M+MQ== X-Gm-Message-State: AOAM5328h+uF8ZGoYWb2J7aqH7tPgiVR7Q3uUY1DXyFid/F7+sL8HG6x LtmeDJOYQ6/7p3I4OSIH0oM= X-Google-Smtp-Source: ABdhPJx+F+vy3/OxAlCs6LGIrtGmdduva4wi4tRr9T6hBpSbW9CIXvc7HHH7d9jGUoAUUdQgrWfViQ== X-Received: by 2002:a17:903:31cd:b0:134:5b6f:2ff8 with SMTP id v13-20020a17090331cd00b001345b6f2ff8mr5521620ple.46.1629738935621; Mon, 23 Aug 2021 10:15:35 -0700 (PDT) Received: from localhost.localdomain ([118.200.190.93]) by smtp.gmail.com with ESMTPSA id q4sm14290830pjd.52.2021.08.23.10.15.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 23 Aug 2021 10:15:35 -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, Daniel Vetter Subject: [PATCH v5 4/6] drm: avoid races with modesetting rights Date: Tue, 24 Aug 2021 01:14:35 +0800 Message-Id: <20210823171437.829404-5-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 Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org In drm_client_modeset.c and drm_fb_helper.c, drm_master_internal_{acquire,release} are used to avoid races with DRM userspace. These functions hold onto drm_device.master_rwsem while committing, and bail if there's already a master. However, there are other places where modesetting rights can race. A time-of-check-to-time-of-use error can occur if an ioctl that changes the modeset has its rights revoked after it validates its permissions, but before it completes. There are four places where modesetting permissions can change: - DROP_MASTER ioctl removes rights for a master and its leases - REVOKE_LEASE ioctl revokes rights for a specific lease - SET_MASTER ioctl sets the device master if the master role hasn't been acquired yet - drm_open which can create a new master for a device if one does not currently exist These races can be avoided using drm_device.master_rwsem: users that perform modesetting should hold a read lock on the new drm_device.master_rwsem, and users that change these permissions should hold a write lock. To avoid deadlocks with master_rwsem, for ioctls that need to check for modesetting permissions, but also need to hold a write lock on master_rwsem to protect some other attribute (or recurses to some function that holds a write lock, like drm_mode_create_lease_ioctl which eventually calls drm_master_open), we remove the DRM_MASTER flag and push the master_rwsem lock and permissions check into the ioctl. Reported-by: Daniel Vetter Signed-off-by: Desmond Cheong Zhi Xi --- drivers/gpu/drm/drm_auth.c | 4 ++++ drivers/gpu/drm/drm_ioctl.c | 20 +++++++++++++++----- drivers/gpu/drm/drm_lease.c | 35 ++++++++++++++++++++++++----------- include/drm/drm_device.h | 5 +++++ 4 files changed, 48 insertions(+), 16 deletions(-) diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c index 73ade0513ccb..65065f7e1499 100644 --- a/drivers/gpu/drm/drm_auth.c +++ b/drivers/gpu/drm/drm_auth.c @@ -120,6 +120,10 @@ int drm_authmagic(struct drm_device *dev, void *data, DRM_DEBUG("%u\n", auth->magic); down_write(&dev->master_rwsem); + if (unlikely(!drm_is_current_master(file_priv))) { + up_write(&dev->master_rwsem); + return -EACCES; + } file = idr_find(&file_priv->master->magic_map, auth->magic); if (file) { file->authenticated = 1; diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c index 158629d88319..8bea39ffc5c0 100644 --- a/drivers/gpu/drm/drm_ioctl.c +++ b/drivers/gpu/drm/drm_ioctl.c @@ -386,6 +386,10 @@ static int drm_setversion(struct drm_device *dev, void *data, struct drm_file *f int if_version, retcode = 0; down_write(&dev->master_rwsem); + if (unlikely(!drm_is_current_master(file_priv))) { + retcode = -EACCES; + goto unlock; + } if (sv->drm_di_major != -1) { if (sv->drm_di_major != DRM_IF_MAJOR || sv->drm_di_minor < 0 || sv->drm_di_minor > DRM_IF_MINOR) { @@ -420,8 +424,9 @@ static int drm_setversion(struct drm_device *dev, void *data, struct drm_file *f sv->drm_di_minor = DRM_IF_MINOR; sv->drm_dd_major = dev->driver->major; sv->drm_dd_minor = dev->driver->minor; - up_write(&dev->master_rwsem); +unlock: + up_write(&dev->master_rwsem); return retcode; } @@ -574,12 +579,12 @@ static const struct drm_ioctl_desc drm_ioctls[] = { DRM_IOCTL_DEF(DRM_IOCTL_GET_STATS, drm_getstats, 0), DRM_IOCTL_DEF(DRM_IOCTL_GET_CAP, drm_getcap, DRM_RENDER_ALLOW), DRM_IOCTL_DEF(DRM_IOCTL_SET_CLIENT_CAP, drm_setclientcap, 0), - DRM_IOCTL_DEF(DRM_IOCTL_SET_VERSION, drm_setversion, DRM_MASTER), + DRM_IOCTL_DEF(DRM_IOCTL_SET_VERSION, drm_setversion, 0), DRM_IOCTL_DEF(DRM_IOCTL_SET_UNIQUE, drm_invalid_op, DRM_AUTH|DRM_MASTER|DRM_ROOT_ONLY), DRM_IOCTL_DEF(DRM_IOCTL_BLOCK, drm_noop, DRM_AUTH|DRM_MASTER|DRM_ROOT_ONLY), DRM_IOCTL_DEF(DRM_IOCTL_UNBLOCK, drm_noop, DRM_AUTH|DRM_MASTER|DRM_ROOT_ONLY), - DRM_IOCTL_DEF(DRM_IOCTL_AUTH_MAGIC, drm_authmagic, DRM_MASTER), + DRM_IOCTL_DEF(DRM_IOCTL_AUTH_MAGIC, drm_authmagic, 0), DRM_LEGACY_IOCTL_DEF(DRM_IOCTL_ADD_MAP, drm_legacy_addmap_ioctl, DRM_AUTH|DRM_MASTER|DRM_ROOT_ONLY), DRM_LEGACY_IOCTL_DEF(DRM_IOCTL_RM_MAP, drm_legacy_rmmap_ioctl, DRM_AUTH), @@ -706,10 +711,10 @@ static const struct drm_ioctl_desc drm_ioctls[] = { DRM_RENDER_ALLOW), DRM_IOCTL_DEF(DRM_IOCTL_CRTC_GET_SEQUENCE, drm_crtc_get_sequence_ioctl, 0), DRM_IOCTL_DEF(DRM_IOCTL_CRTC_QUEUE_SEQUENCE, drm_crtc_queue_sequence_ioctl, 0), - DRM_IOCTL_DEF(DRM_IOCTL_MODE_CREATE_LEASE, drm_mode_create_lease_ioctl, DRM_MASTER), + DRM_IOCTL_DEF(DRM_IOCTL_MODE_CREATE_LEASE, drm_mode_create_lease_ioctl, 0), DRM_IOCTL_DEF(DRM_IOCTL_MODE_LIST_LESSEES, drm_mode_list_lessees_ioctl, DRM_MASTER), DRM_IOCTL_DEF(DRM_IOCTL_MODE_GET_LEASE, drm_mode_get_lease_ioctl, DRM_MASTER), - DRM_IOCTL_DEF(DRM_IOCTL_MODE_REVOKE_LEASE, drm_mode_revoke_lease_ioctl, DRM_MASTER), + DRM_IOCTL_DEF(DRM_IOCTL_MODE_REVOKE_LEASE, drm_mode_revoke_lease_ioctl, 0), }; #define DRM_CORE_IOCTL_COUNT ARRAY_SIZE( drm_ioctls ) @@ -776,6 +781,9 @@ long drm_ioctl_kernel(struct file *file, drm_ioctl_t *func, void *kdata, if (unlikely(drm_core_check_feature(dev, DRIVER_LEGACY)) && !(flags & DRM_UNLOCKED)) mutex_lock(&drm_global_mutex); + if (unlikely(flags & DRM_MASTER)) + down_read(&dev->master_rwsem); + retcode = drm_ioctl_permit(flags, file_priv); if (unlikely(retcode)) goto out; @@ -783,6 +791,8 @@ long drm_ioctl_kernel(struct file *file, drm_ioctl_t *func, void *kdata, retcode = func(dev, kdata, file_priv); out: + if (unlikely(flags & DRM_MASTER)) + up_read(&dev->master_rwsem); if (unlikely(drm_core_check_feature(dev, DRIVER_LEGACY)) && !(flags & DRM_UNLOCKED)) mutex_unlock(&drm_global_mutex); return retcode; diff --git a/drivers/gpu/drm/drm_lease.c b/drivers/gpu/drm/drm_lease.c index dee4f24a1808..bed6f7636cbe 100644 --- a/drivers/gpu/drm/drm_lease.c +++ b/drivers/gpu/drm/drm_lease.c @@ -500,6 +500,18 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, return -EINVAL; } + /* Clone the lessor file to create a new file for us */ + DRM_DEBUG_LEASE("Allocating lease file\n"); + lessee_file = file_clone_open(lessor_file); + if (IS_ERR(lessee_file)) + return PTR_ERR(lessee_file); + + down_read(&dev->master_rwsem); + if (unlikely(!drm_is_current_master(lessor_priv))) { + ret = -EACCES; + goto out_file; + } + lessor = drm_file_get_master(lessor_priv); /* Do not allow sub-leases */ if (lessor->lessor) { @@ -547,14 +559,6 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, goto out_leases; } - /* Clone the lessor file to create a new file for us */ - DRM_DEBUG_LEASE("Allocating lease file\n"); - lessee_file = file_clone_open(lessor_file); - if (IS_ERR(lessee_file)) { - ret = PTR_ERR(lessee_file); - goto out_lessee; - } - lessee_priv = lessee_file->private_data; /* Change the file to a master one */ drm_master_put(&lessee_priv->master); @@ -571,17 +575,19 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, fd_install(fd, lessee_file); drm_master_put(&lessor); + up_read(&dev->master_rwsem); DRM_DEBUG_LEASE("drm_mode_create_lease_ioctl succeeded\n"); return 0; -out_lessee: - drm_master_put(&lessee); - out_leases: put_unused_fd(fd); out_lessor: drm_master_put(&lessor); + +out_file: + up_read(&dev->master_rwsem); + fput(lessee_file); DRM_DEBUG_LEASE("drm_mode_create_lease_ioctl failed: %d\n", ret); return ret; } @@ -705,6 +711,11 @@ int drm_mode_revoke_lease_ioctl(struct drm_device *dev, if (!drm_core_check_feature(dev, DRIVER_MODESET)) return -EOPNOTSUPP; + down_write(&dev->master_rwsem); + if (unlikely(!drm_is_current_master(lessor_priv))) { + ret = -EACCES; + goto unlock; + } lessor = drm_file_get_master(lessor_priv); mutex_lock(&dev->mode_config.idr_mutex); @@ -728,5 +739,7 @@ int drm_mode_revoke_lease_ioctl(struct drm_device *dev, mutex_unlock(&dev->mode_config.idr_mutex); drm_master_put(&lessor); +unlock: + up_write(&dev->master_rwsem); return ret; } diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h index 142fb2f6e74d..7d32bb69e6db 100644 --- a/include/drm/drm_device.h +++ b/include/drm/drm_device.h @@ -151,6 +151,11 @@ struct drm_device { * Lock for &drm_device.master, &drm_file.was_master, * &drm_file.is_master, &drm_file.master, &drm_master.unique, * &drm_master.unique_len, and &drm_master.magic_map. + * + * Additionally, synchronizes modesetting rights between multiple users. + * Users that can change the modeset or display state must hold a read + * lock on @master_rwsem, and users that change modesetting rights + * should hold a write lock. */ struct rw_semaphore master_rwsem; 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Mon, 23 Aug 2021 10:15:41 -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 5/6] drm: avoid circular locks with modeset_mutex and master_rwsem Date: Tue, 24 Aug 2021 01:14:36 +0800 Message-Id: <20210823171437.829404-6-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 Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org drm_device.master_rwsem is an outer lock that's grabbed in the ioctl handler. However, in a future patch, master_rwsem will replace drm_file.master_lookup_lock in drm_file_get_master, which is sometimes called while holding other locks that depend on master_rwsem. This circular locking should be avoided to prevent deadlocks. _drm_lease_held and drm_lease_held call drm_file_get_master. However, both functions are called while holding on to modeset_mutex, inverting the master_rwsem --> modeset_mutex lock hierarchy. To fix this, we do two things: 1. Wrap __drm_mode_object_find with read locks on master_rwsem before locking modeset mutex so that we can still safely access drm_file.master without drm_file_get_master 2. Call drm_file_get_master before locking modeset_mutex, then check for leases with the new drm_lease_held_master function instead of drm_lease_held Signed-off-by: Desmond Cheong Zhi Xi --- drivers/gpu/drm/drm_atomic_uapi.c | 4 +++- drivers/gpu/drm/drm_auth.c | 3 +++ drivers/gpu/drm/drm_encoder.c | 7 ++++++- drivers/gpu/drm/drm_framebuffer.c | 2 +- drivers/gpu/drm/drm_lease.c | 34 ++++++++----------------------- drivers/gpu/drm/drm_mode_object.c | 16 +++++++++++---- drivers/gpu/drm/drm_plane.c | 17 +++++++++++++--- drivers/gpu/drm/drm_property.c | 6 +++--- include/drm/drm_lease.h | 4 +++- 9 files changed, 53 insertions(+), 40 deletions(-) diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c index 909f31833181..203b0936f7f4 100644 --- a/drivers/gpu/drm/drm_atomic_uapi.c +++ b/drivers/gpu/drm/drm_atomic_uapi.c @@ -1366,6 +1366,7 @@ int drm_mode_atomic_ioctl(struct drm_device *dev, if (!state) return -ENOMEM; + down_read(&dev->master_rwsem); drm_modeset_acquire_init(&ctx, DRM_MODESET_ACQUIRE_INTERRUPTIBLE); state->acquire_ctx = &ctx; state->allow_modeset = !!(arg->flags & DRM_MODE_ATOMIC_ALLOW_MODESET); @@ -1385,7 +1386,7 @@ int drm_mode_atomic_ioctl(struct drm_device *dev, goto out; } - obj = drm_mode_object_find(dev, file_priv, obj_id, DRM_MODE_OBJECT_ANY); + obj = __drm_mode_object_find(dev, file_priv, obj_id, DRM_MODE_OBJECT_ANY); if (!obj) { ret = -ENOENT; goto out; @@ -1474,6 +1475,7 @@ int drm_mode_atomic_ioctl(struct drm_device *dev, drm_modeset_drop_locks(&ctx); drm_modeset_acquire_fini(&ctx); + up_read(&dev->master_rwsem); return ret; } diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c index 65065f7e1499..f2b2f197052a 100644 --- a/drivers/gpu/drm/drm_auth.c +++ b/drivers/gpu/drm/drm_auth.c @@ -410,6 +410,9 @@ struct drm_master *drm_file_get_master(struct drm_file *file_priv) { struct drm_master *master = NULL; + if (!file_priv) + return NULL; + spin_lock(&file_priv->master_lookup_lock); if (!file_priv->master) goto unlock; diff --git a/drivers/gpu/drm/drm_encoder.c b/drivers/gpu/drm/drm_encoder.c index 72e982323a5e..a4852876f91f 100644 --- a/drivers/gpu/drm/drm_encoder.c +++ b/drivers/gpu/drm/drm_encoder.c @@ -22,6 +22,7 @@ #include +#include #include #include #include @@ -281,6 +282,7 @@ int drm_mode_getencoder(struct drm_device *dev, void *data, struct drm_mode_get_encoder *enc_resp = data; struct drm_encoder *encoder; struct drm_crtc *crtc; + struct drm_master *master = NULL; if (!drm_core_check_feature(dev, DRIVER_MODESET)) return -EOPNOTSUPP; @@ -289,13 +291,16 @@ int drm_mode_getencoder(struct drm_device *dev, void *data, if (!encoder) return -ENOENT; + master = drm_file_get_master(file_priv); drm_modeset_lock(&dev->mode_config.connection_mutex, NULL); crtc = drm_encoder_get_crtc(encoder); - if (crtc && drm_lease_held(file_priv, crtc->base.id)) + if (crtc && drm_lease_held_master(master, crtc->base.id)) enc_resp->crtc_id = crtc->base.id; else enc_resp->crtc_id = 0; drm_modeset_unlock(&dev->mode_config.connection_mutex); + if (master) + drm_master_put(&master); enc_resp->encoder_type = encoder->encoder_type; enc_resp->encoder_id = encoder->base.id; diff --git a/drivers/gpu/drm/drm_framebuffer.c b/drivers/gpu/drm/drm_framebuffer.c index 07f5abc875e9..9c1db91b150d 100644 --- a/drivers/gpu/drm/drm_framebuffer.c +++ b/drivers/gpu/drm/drm_framebuffer.c @@ -887,7 +887,7 @@ struct drm_framebuffer *drm_framebuffer_lookup(struct drm_device *dev, struct drm_mode_object *obj; struct drm_framebuffer *fb = NULL; - obj = __drm_mode_object_find(dev, file_priv, id, DRM_MODE_OBJECT_FB); + obj = drm_mode_object_find(dev, file_priv, id, DRM_MODE_OBJECT_FB); if (obj) fb = obj_to_fb(obj); return fb; diff --git a/drivers/gpu/drm/drm_lease.c b/drivers/gpu/drm/drm_lease.c index bed6f7636cbe..4d434ee6730d 100644 --- a/drivers/gpu/drm/drm_lease.c +++ b/drivers/gpu/drm/drm_lease.c @@ -85,7 +85,7 @@ _drm_find_lessee(struct drm_master *master, int lessee_id) return idr_find(&drm_lease_owner(master)->lessee_idr, lessee_id); } -static int _drm_lease_held_master(struct drm_master *master, int id) +bool _drm_lease_held_master(struct drm_master *master, int id) { lockdep_assert_held(&master->dev->mode_config.idr_mutex); if (master->lessor) @@ -105,20 +105,16 @@ static bool _drm_has_leased(struct drm_master *master, int id) return false; } -/* Called with idr_mutex held */ -bool _drm_lease_held(struct drm_file *file_priv, int id) +bool drm_lease_held_master(struct drm_master *master, int id) { bool ret; - struct drm_master *master; - if (!file_priv) + if (!master || !master->lessor) return true; - master = drm_file_get_master(file_priv); - if (!master) - return true; + mutex_lock(&master->dev->mode_config.idr_mutex); ret = _drm_lease_held_master(master, id); - drm_master_put(&master); + mutex_unlock(&master->dev->mode_config.idr_mutex); return ret; } @@ -128,22 +124,11 @@ bool drm_lease_held(struct drm_file *file_priv, int id) struct drm_master *master; bool ret; - if (!file_priv) - return true; - master = drm_file_get_master(file_priv); - if (!master) - return true; - if (!master->lessor) { - ret = true; - goto out; - } - mutex_lock(&master->dev->mode_config.idr_mutex); - ret = _drm_lease_held_master(master, id); - mutex_unlock(&master->dev->mode_config.idr_mutex); + ret = drm_lease_held_master(master, id); + if (master) + drm_master_put(&master); -out: - drm_master_put(&master); return ret; } @@ -159,9 +144,6 @@ 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) - return crtcs_in; - master = drm_file_get_master(file_priv); if (!master) return crtcs_in; diff --git a/drivers/gpu/drm/drm_mode_object.c b/drivers/gpu/drm/drm_mode_object.c index 86d9e907c0b2..911f658a8ffc 100644 --- a/drivers/gpu/drm/drm_mode_object.c +++ b/drivers/gpu/drm/drm_mode_object.c @@ -139,6 +139,7 @@ struct drm_mode_object *__drm_mode_object_find(struct drm_device *dev, { struct drm_mode_object *obj = NULL; + lockdep_assert_held_once(&dev->master_rwsem); mutex_lock(&dev->mode_config.idr_mutex); obj = idr_find(&dev->mode_config.object_idr, id); if (obj && type != DRM_MODE_OBJECT_ANY && obj->type != type) @@ -146,9 +147,11 @@ struct drm_mode_object *__drm_mode_object_find(struct drm_device *dev, if (obj && obj->id != id) obj = NULL; - if (obj && drm_mode_object_lease_required(obj->type) && - !_drm_lease_held(file_priv, obj->id)) - obj = NULL; + if (obj && drm_mode_object_lease_required(obj->type)) { + if (file_priv && file_priv->master && + !_drm_lease_held_master(file_priv->master, obj->id)) + obj = NULL; + } if (obj && obj->free_cb) { if (!kref_get_unless_zero(&obj->refcount)) @@ -176,7 +179,9 @@ struct drm_mode_object *drm_mode_object_find(struct drm_device *dev, { struct drm_mode_object *obj = NULL; + down_read(&dev->master_rwsem); obj = __drm_mode_object_find(dev, file_priv, id, type); + up_read(&dev->master_rwsem); return obj; } EXPORT_SYMBOL(drm_mode_object_find); @@ -408,9 +413,12 @@ int drm_mode_obj_get_properties_ioctl(struct drm_device *dev, void *data, if (!drm_core_check_feature(dev, DRIVER_MODESET)) return -EOPNOTSUPP; + down_read(&dev->master_rwsem); DRM_MODESET_LOCK_ALL_BEGIN(dev, ctx, 0, ret); - obj = drm_mode_object_find(dev, file_priv, arg->obj_id, arg->obj_type); + obj = __drm_mode_object_find(dev, file_priv, arg->obj_id, + arg->obj_type); + up_read(&dev->master_rwsem); if (!obj) { ret = -ENOENT; goto out; diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c index 82afb854141b..90f056169331 100644 --- a/drivers/gpu/drm/drm_plane.c +++ b/drivers/gpu/drm/drm_plane.c @@ -23,6 +23,7 @@ #include #include +#include #include #include #include @@ -687,6 +688,7 @@ int drm_mode_getplane(struct drm_device *dev, void *data, struct drm_mode_get_plane *plane_resp = data; struct drm_plane *plane; uint32_t __user *format_ptr; + struct drm_master *master = NULL; if (!drm_core_check_feature(dev, DRIVER_MODESET)) return -EOPNOTSUPP; @@ -695,10 +697,13 @@ int drm_mode_getplane(struct drm_device *dev, void *data, if (!plane) return -ENOENT; + master = drm_file_get_master(file_priv); drm_modeset_lock(&plane->mutex, NULL); - if (plane->state && plane->state->crtc && drm_lease_held(file_priv, plane->state->crtc->base.id)) + if (plane->state && plane->state->crtc && + drm_lease_held_master(master, plane->state->crtc->base.id)) plane_resp->crtc_id = plane->state->crtc->base.id; - else if (!plane->state && plane->crtc && drm_lease_held(file_priv, plane->crtc->base.id)) + else if (!plane->state && plane->crtc && + drm_lease_held_master(master, plane->crtc->base.id)) plane_resp->crtc_id = plane->crtc->base.id; else plane_resp->crtc_id = 0; @@ -710,6 +715,8 @@ int drm_mode_getplane(struct drm_device *dev, void *data, else plane_resp->fb_id = 0; drm_modeset_unlock(&plane->mutex); + if (master) + drm_master_put(&master); plane_resp->plane_id = plane->base.id; plane_resp->possible_crtcs = drm_lease_filter_crtcs(file_priv, @@ -1100,6 +1107,7 @@ static int drm_mode_cursor_common(struct drm_device *dev, { struct drm_crtc *crtc; struct drm_modeset_acquire_ctx ctx; + struct drm_master *master = NULL; int ret = 0; if (!drm_core_check_feature(dev, DRIVER_MODESET)) @@ -1114,6 +1122,7 @@ static int drm_mode_cursor_common(struct drm_device *dev, return -ENOENT; } + master = drm_file_get_master(file_priv); drm_modeset_acquire_init(&ctx, DRM_MODESET_ACQUIRE_INTERRUPTIBLE); retry: ret = drm_modeset_lock(&crtc->mutex, &ctx); @@ -1128,7 +1137,7 @@ static int drm_mode_cursor_common(struct drm_device *dev, if (ret) goto out; - if (!drm_lease_held(file_priv, crtc->cursor->base.id)) { + if (!drm_lease_held_master(master, crtc->cursor->base.id)) { ret = -EACCES; goto out; } @@ -1168,6 +1177,8 @@ static int drm_mode_cursor_common(struct drm_device *dev, drm_modeset_drop_locks(&ctx); drm_modeset_acquire_fini(&ctx); + if (master) + drm_master_put(&master); return ret; diff --git a/drivers/gpu/drm/drm_property.c b/drivers/gpu/drm/drm_property.c index 6c353c9dc772..9f04dcb81d07 100644 --- a/drivers/gpu/drm/drm_property.c +++ b/drivers/gpu/drm/drm_property.c @@ -656,7 +656,7 @@ struct drm_property_blob *drm_property_lookup_blob(struct drm_device *dev, struct drm_mode_object *obj; struct drm_property_blob *blob = NULL; - obj = __drm_mode_object_find(dev, NULL, id, DRM_MODE_OBJECT_BLOB); + obj = drm_mode_object_find(dev, NULL, id, DRM_MODE_OBJECT_BLOB); if (obj) blob = obj_to_blob(obj); return blob; @@ -919,8 +919,8 @@ bool drm_property_change_valid_get(struct drm_property *property, if (value == 0) return true; - *ref = __drm_mode_object_find(property->dev, NULL, value, - property->values[0]); + *ref = drm_mode_object_find(property->dev, NULL, value, + property->values[0]); return *ref != NULL; } diff --git a/include/drm/drm_lease.h b/include/drm/drm_lease.h index 5c9ef6a2aeae..62d9de6ecada 100644 --- a/include/drm/drm_lease.h +++ b/include/drm/drm_lease.h @@ -16,7 +16,9 @@ void drm_lease_destroy(struct drm_master *lessee); bool drm_lease_held(struct drm_file *file_priv, int id); -bool _drm_lease_held(struct drm_file *file_priv, int id); +bool _drm_lease_held_master(struct drm_master *master, int id); + +bool drm_lease_held_master(struct drm_master *master, int id); void drm_lease_revoke(struct drm_master *master);