From patchwork Mon Jul 12 04:35:04 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: 12370167 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,URIBL_BLOCKED, 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 346A1C07E9B for ; Mon, 12 Jul 2021 04:35:58 +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 D589C60FF1 for ; Mon, 12 Jul 2021 04:35:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D589C60FF1 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 350A089BC0; Mon, 12 Jul 2021 04:35:57 +0000 (UTC) Received: from mail-pf1-x432.google.com (mail-pf1-x432.google.com [IPv6:2607:f8b0:4864:20::432]) by gabe.freedesktop.org (Postfix) with ESMTPS id 7B49189BC0; Mon, 12 Jul 2021 04:35:56 +0000 (UTC) Received: by mail-pf1-x432.google.com with SMTP id 17so15241619pfz.4; Sun, 11 Jul 2021 21:35:56 -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=vc5xi5ftWnxZlU1gt0+b48wT38LyZFngC4JD9PKuX7I=; b=Cb3M3vkk3FuoDtvFBvEh8156faQwTUThdp+n0uUYWQBYv3ouu9t5ZNGd5SwrKX67Kt vl0hi9W3WmsJuZDYRTmIOr+4DeklTVF04l28vjLZf5qufrBH0FT1YD5Pslug4BG3Wtoe 8AkwcOysJKQ6LzJP7JdbshGQu2qBgqICEslwnsXZ8jA0qGT1eqQko7RbSSIeNPZ0Wg4k HH6HAbsBVycseDYivQSwfVgRRi5N2iUJFGEcs38O1flBvrS0sNwNE4s7mek9uJCX67nY vZlOk9uRf2EmQ82ji96k3z3Z44BH3NKnBA78PtKalqTnCAMqh7uHRPCe7v3VojaTKZGx PGMQ== 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=vc5xi5ftWnxZlU1gt0+b48wT38LyZFngC4JD9PKuX7I=; b=TlGyg+PJAQrqDNbIwYkwQybzadtDXFeZ18FrHjlSBx/jiU845iXyy6fqcsue1KYx/t r5CX+sxqxRZqeS1gf9Kum+RTh7NKHltOU98EfOFblqhw3OBq3frp3CWWAVTlAWoH7dWs X6QVW8VDyIit6ojU0k/5+c2fZv8a/vIaayfrJLhVYBodUnyhrAuygb3X2Lk1+3G9/WUz ybVPojCmOvj91oKD6Sb+6A45E27NTzVnt11/2ah5Tv3oWtco6V71LvylWa+6KE0+w7xD PKuqWOUfmYrjBujxDpdXEzkphEp2QbGMskBpQdU8+n6EIELUzkX3Zw2HoLMoUsqkVgxG Xu6w== X-Gm-Message-State: AOAM5309lXGXwxPUzvcHu7UHClMCDzBPn3hWnkzQlR7Cq+F71Uwek2Le Z03YzDYfI5KAgG0OxCr8z/0= X-Google-Smtp-Source: ABdhPJxCujRkDQjCW3B0eNy7eTGjw4nq7M1Kn3DT88JRrgd3WhjryI26Pk/IICRmxm9iWx/UrR5ZbA== X-Received: by 2002:a63:f241:: with SMTP id d1mr2270900pgk.424.1626064556049; Sun, 11 Jul 2021 21:35:56 -0700 (PDT) Received: from localhost.localdomain ([118.200.190.93]) by smtp.gmail.com with ESMTPSA id n3sm14242764pfn.216.2021.07.11.21.35.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 11 Jul 2021 21:35:55 -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 v8 1/5] drm: avoid circular locks in drm_mode_getconnector Date: Mon, 12 Jul 2021 12:35:04 +0800 Message-Id: <20210712043508.11584-2-desmondcheongzx@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210712043508.11584-1-desmondcheongzx@gmail.com> References: <20210712043508.11584-1-desmondcheongzx@gmail.com> MIME-Version: 1.0 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" In preparation for a future patch to take a lock on drm_device.master_mutex inside drm_is_current_master(), we first move the call to drm_is_current_master() in drm_mode_getconnector out from the section locked by &dev->mode_config.mutex. This avoids creating a circular lock dependency. Failing to avoid this lock dependency produces the following lockdep splat: ====================================================== WARNING: possible circular locking dependency detected 5.13.0-rc7-CI-CI_DRM_10254+ #1 Not tainted ------------------------------------------------------ kms_frontbuffer/1087 is trying to acquire lock: ffff88810dcd01a8 (&dev->master_mutex){+.+.}-{3:3}, at: drm_is_current_master+0x1b/0x40 but task is already holding lock: ffff88810dcd0488 (&dev->mode_config.mutex){+.+.}-{3:3}, at: drm_mode_getconnector+0x1c6/0x4a0 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&dev->mode_config.mutex){+.+.}-{3:3}: __mutex_lock+0xab/0x970 drm_client_modeset_probe+0x22e/0xca0 __drm_fb_helper_initial_config_and_unlock+0x42/0x540 intel_fbdev_initial_config+0xf/0x20 [i915] async_run_entry_fn+0x28/0x130 process_one_work+0x26d/0x5c0 worker_thread+0x37/0x380 kthread+0x144/0x170 ret_from_fork+0x1f/0x30 -> #1 (&client->modeset_mutex){+.+.}-{3:3}: __mutex_lock+0xab/0x970 drm_client_modeset_commit_locked+0x1c/0x180 drm_client_modeset_commit+0x1c/0x40 __drm_fb_helper_restore_fbdev_mode_unlocked+0x88/0xb0 drm_fb_helper_set_par+0x34/0x40 intel_fbdev_set_par+0x11/0x40 [i915] fbcon_init+0x270/0x4f0 visual_init+0xc6/0x130 do_bind_con_driver+0x1e5/0x2d0 do_take_over_console+0x10e/0x180 do_fbcon_takeover+0x53/0xb0 register_framebuffer+0x22d/0x310 __drm_fb_helper_initial_config_and_unlock+0x36c/0x540 intel_fbdev_initial_config+0xf/0x20 [i915] async_run_entry_fn+0x28/0x130 process_one_work+0x26d/0x5c0 worker_thread+0x37/0x380 kthread+0x144/0x170 ret_from_fork+0x1f/0x30 -> #0 (&dev->master_mutex){+.+.}-{3:3}: __lock_acquire+0x151e/0x2590 lock_acquire+0xd1/0x3d0 __mutex_lock+0xab/0x970 drm_is_current_master+0x1b/0x40 drm_mode_getconnector+0x37e/0x4a0 drm_ioctl_kernel+0xa8/0xf0 drm_ioctl+0x1e8/0x390 __x64_sys_ioctl+0x6a/0xa0 do_syscall_64+0x39/0xb0 entry_SYSCALL_64_after_hwframe+0x44/0xae other info that might help us debug this: Chain exists of: &dev->master_mutex --> &client->modeset_mutex --> &dev->mode_config.mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&dev->mode_config.mutex); lock(&client->modeset_mutex); lock(&dev->mode_config.mutex); lock(&dev->master_mutex); *** DEADLOCK *** 1 lock held by kms_frontbuffer/1087: #0: ffff88810dcd0488 (&dev->mode_config.mutex){+.+.}-{3:3}, at: drm_mode_getconnector+0x1c6/0x4a0 stack backtrace: CPU: 7 PID: 1087 Comm: kms_frontbuffer Not tainted 5.13.0-rc7-CI-CI_DRM_10254+ #1 Hardware name: Intel Corporation Ice Lake Client Platform/IceLake U DDR4 SODIMM PD RVP TLC, BIOS ICLSFWR1.R00.3234.A01.1906141750 06/14/2019 Call Trace: dump_stack+0x7f/0xad check_noncircular+0x12e/0x150 __lock_acquire+0x151e/0x2590 lock_acquire+0xd1/0x3d0 __mutex_lock+0xab/0x970 drm_is_current_master+0x1b/0x40 drm_mode_getconnector+0x37e/0x4a0 drm_ioctl_kernel+0xa8/0xf0 drm_ioctl+0x1e8/0x390 __x64_sys_ioctl+0x6a/0xa0 do_syscall_64+0x39/0xb0 entry_SYSCALL_64_after_hwframe+0x44/0xae Reported-by: Daniel Vetter Signed-off-by: Desmond Cheong Zhi Xi Reviewed-by: Emil Velikov --- drivers/gpu/drm/drm_connector.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c index da39e7ff6965..2ba257b1ae20 100644 --- a/drivers/gpu/drm/drm_connector.c +++ b/drivers/gpu/drm/drm_connector.c @@ -2414,6 +2414,7 @@ int drm_mode_getconnector(struct drm_device *dev, void *data, struct drm_mode_modeinfo u_mode; struct drm_mode_modeinfo __user *mode_ptr; uint32_t __user *encoder_ptr; + bool is_current_master; if (!drm_core_check_feature(dev, DRIVER_MODESET)) return -EOPNOTSUPP; @@ -2444,9 +2445,11 @@ int drm_mode_getconnector(struct drm_device *dev, void *data, out_resp->connector_type = connector->connector_type; out_resp->connector_type_id = connector->connector_type_id; + is_current_master = drm_is_current_master(file_priv); + mutex_lock(&dev->mode_config.mutex); if (out_resp->count_modes == 0) { - if (drm_is_current_master(file_priv)) + if (is_current_master) connector->funcs->fill_modes(connector, dev->mode_config.max_width, dev->mode_config.max_height); From patchwork Mon Jul 12 04:35:05 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: 12370169 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=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 75344C07E99 for ; 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Sun, 11 Jul 2021 21:36:01 -0700 (PDT) Received: from localhost.localdomain ([118.200.190.93]) by smtp.gmail.com with ESMTPSA id n3sm14242764pfn.216.2021.07.11.21.35.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 11 Jul 2021 21:36:01 -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 v8 2/5] drm: avoid blocking in drm_clients_info's rcu section Date: Mon, 12 Jul 2021 12:35:05 +0800 Message-Id: <20210712043508.11584-3-desmondcheongzx@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210712043508.11584-1-desmondcheongzx@gmail.com> References: <20210712043508.11584-1-desmondcheongzx@gmail.com> MIME-Version: 1.0 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: 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" Inside drm_clients_info, the rcu_read_lock is held to lock pid_task()->comm. However, within this protected section, a call to drm_is_current_master is made, which involves a mutex lock in a future patch. However, this is illegal because the mutex lock might block while in the RCU read-side critical section. Since drm_is_current_master isn't protected by rcu_read_lock, we avoid this by moving it out of the RCU critical section. The following report came from intel-gfx ci's igt@debugfs_test@read_all_entries testcase: ============================= [ BUG: Invalid wait context ] 5.13.0-CI-Patchwork_20515+ #1 Tainted: G W ----------------------------- debugfs_test/1101 is trying to lock: ffff888132d901a8 (&dev->master_mutex){+.+.}-{3:3}, at: drm_is_current_master+0x1e/0x50 other info that might help us debug this: context-{4:4} 3 locks held by debugfs_test/1101: #0: ffff88810fdffc90 (&p->lock){+.+.}-{3:3}, at: seq_read_iter+0x53/0x3b0 #1: ffff888132d90240 (&dev->filelist_mutex){+.+.}-{3:3}, at: drm_clients_info+0x63/0x2a0 #2: ffffffff82734220 (rcu_read_lock){....}-{1:2}, at: drm_clients_info+0x1b1/0x2a0 stack backtrace: CPU: 8 PID: 1101 Comm: debugfs_test Tainted: G W 5.13.0-CI-Patchwork_20515+ #1 Hardware name: Intel Corporation CometLake Client Platform/CometLake S UDIMM (ERB/CRB), BIOS CMLSFWR1.R00.1263.D00.1906260926 06/26/2019 Call Trace: dump_stack+0x7f/0xad __lock_acquire.cold.78+0x2af/0x2ca lock_acquire+0xd3/0x300 ? drm_is_current_master+0x1e/0x50 ? __mutex_lock+0x76/0x970 ? lockdep_hardirqs_on+0xbf/0x130 __mutex_lock+0xab/0x970 ? drm_is_current_master+0x1e/0x50 ? drm_is_current_master+0x1e/0x50 ? drm_is_current_master+0x1e/0x50 drm_is_current_master+0x1e/0x50 drm_clients_info+0x107/0x2a0 seq_read_iter+0x178/0x3b0 seq_read+0x104/0x150 full_proxy_read+0x4e/0x80 vfs_read+0xa5/0x1b0 ksys_read+0x5a/0xd0 do_syscall_64+0x39/0xb0 entry_SYSCALL_64_after_hwframe+0x44/0xae Signed-off-by: Desmond Cheong Zhi Xi --- drivers/gpu/drm/drm_debugfs.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/drm_debugfs.c b/drivers/gpu/drm/drm_debugfs.c index 3d7182001004..b0a826489488 100644 --- a/drivers/gpu/drm/drm_debugfs.c +++ b/drivers/gpu/drm/drm_debugfs.c @@ -91,6 +91,7 @@ static int drm_clients_info(struct seq_file *m, void *data) mutex_lock(&dev->filelist_mutex); list_for_each_entry_reverse(priv, &dev->filelist, lhead) { struct task_struct *task; + bool is_current_master = drm_is_current_master(priv); rcu_read_lock(); /* locks pid_task()->comm */ task = pid_task(priv->pid, PIDTYPE_PID); @@ -99,7 +100,7 @@ static int drm_clients_info(struct seq_file *m, void *data) task ? task->comm : "", pid_vnr(priv->pid), priv->minor->index, - drm_is_current_master(priv) ? 'y' : 'n', + is_current_master ? 'y' : 'n', priv->authenticated ? 'y' : 'n', from_kuid_munged(seq_user_ns(m), uid), priv->magic); From patchwork Mon Jul 12 04:35:06 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Desmond Cheong Zhi Xi X-Patchwork-Id: 12370171 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,URIBL_BLOCKED, 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 A65C3C07E9C for ; Mon, 12 Jul 2021 04:36:08 +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 6C0F0610D0 for ; Mon, 12 Jul 2021 04:36:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6C0F0610D0 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id E9F7189BF1; Mon, 12 Jul 2021 04:36:07 +0000 (UTC) Received: from mail-pg1-x534.google.com (mail-pg1-x534.google.com [IPv6:2607:f8b0:4864:20::534]) by gabe.freedesktop.org (Postfix) with ESMTPS id 7455C89BF1; Mon, 12 Jul 2021 04:36:07 +0000 (UTC) Received: by mail-pg1-x534.google.com with SMTP id 62so17012295pgf.1; Sun, 11 Jul 2021 21:36:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=CtdxbqSeV/2csKmNSvUS45gYT6/rPtvycxiemXQFqoE=; b=RkEVvjOYkpwdKOPg3pFGyZ+MmtY9Q6jyGy9uT18j8G2Y0B21jpq+qci03i9JMuQ+iv 3z/kr1Pf/aVNk9F5G8cbnU8ty+vr9/Dd4WL1XF9A1LmI8s6cHN4pAS6JC1o38oeJF5ek Eofy/TrzJ2b7IeTtAT7Ry1D9RINbF3rkJMgaHRIn5z/quGWmtgDA4WiBElGU2ZSXWb95 hZ6A+KULPqjOnqaADbeO1+cmK6skjVX4QzorBIolm1wJqxEgELwdZ1ZrS8h+RuhvSI4g 8bcmmqHqYyqjSrWhO4oBSFpXxHI4lW5yz/IM1saDLqFfDcDcNqDY9epj3nY6/nroIogX +q1A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=CtdxbqSeV/2csKmNSvUS45gYT6/rPtvycxiemXQFqoE=; b=IrfZC+57vbWVLmcorkdCIZYuXehZUudqJYqjvXw+p8AdhB9ETY+YFuyZW1svpBxQFC mZyPpP+mkyu2BeEH+GtJO1+M+H4W2+z7Nz/oyVw5ABs25ioLt621WWezEijWH5ErL2Bn bwe+YhyaliKw4oGJujGXBmL7+H8zWM8wrAy3z40CHugf5EJ4jByefc+zLDYRUllTJ7pF SRh4TZOtpUGUKeIzupgtSSktOs/LGr0TQkB25UcSrmXvb1DjzPG1vzHohBecaXoBOFEQ FJrLGtxDw60An15/27RP1/H3bZR/4NoGlK+Gr2gIoZTEkVxlLVJgIiHYxZtwh014/iAJ M2Ig== X-Gm-Message-State: AOAM530uD41kUJ9iwoms/lM/HB2uf+yH9i2Mxrm+Vvud8Nq5lEcvkNZg yxiy2nSyE4BeAIzjmR97p0I= X-Google-Smtp-Source: ABdhPJz7q2t2Aox3iXnYKLt/9A+I+u5rTDJ6gGyg8eEi+vSuax0InwQFllAbLpOOEG/5WtqX4FbZPA== X-Received: by 2002:a63:de18:: with SMTP id f24mr45282752pgg.112.1626064567107; Sun, 11 Jul 2021 21:36:07 -0700 (PDT) Received: from localhost.localdomain ([118.200.190.93]) by smtp.gmail.com with ESMTPSA id n3sm14242764pfn.216.2021.07.11.21.36.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 11 Jul 2021 21:36:06 -0700 (PDT) From: Desmond Cheong Zhi Xi To: maarten.lankhorst@linux.intel.com, mripard@kernel.org, tzimmermann@suse.de, airlied@linux.ie, daniel@ffwll.ch, sumit.semwal@linaro.org, christian.koenig@amd.com Subject: [PATCH v8 3/5] drm: add a locked version of drm_is_current_master Date: Mon, 12 Jul 2021 12:35:06 +0800 Message-Id: <20210712043508.11584-4-desmondcheongzx@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210712043508.11584-1-desmondcheongzx@gmail.com> References: <20210712043508.11584-1-desmondcheongzx@gmail.com> MIME-Version: 1.0 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" While checking the master status of the DRM file in drm_is_current_master(), the device's master mutex should be held. Without the mutex, the pointer fpriv->master may be freed concurrently by another process calling drm_setmaster_ioctl(). This could lead to use-after-free errors when the pointer is subsequently dereferenced in drm_lease_owner(). The callers of drm_is_current_master() from drm_auth.c hold the device's master mutex, but external callers do not. Hence, we implement drm_is_current_master_locked() to be used within drm_auth.c, and modify drm_is_current_master() to grab the device's master mutex before checking the master status. Reported-by: Daniel Vetter Signed-off-by: Desmond Cheong Zhi Xi Reviewed-by: Emil Velikov --- drivers/gpu/drm/drm_auth.c | 51 ++++++++++++++++++++++++-------------- 1 file changed, 32 insertions(+), 19 deletions(-) diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c index f00e5abdbbf4..ab1863c5a5a0 100644 --- a/drivers/gpu/drm/drm_auth.c +++ b/drivers/gpu/drm/drm_auth.c @@ -61,6 +61,35 @@ * trusted clients. */ +static bool drm_is_current_master_locked(struct drm_file *fpriv) +{ + lockdep_assert_held_once(&fpriv->minor->dev->master_mutex); + + return fpriv->is_master && drm_lease_owner(fpriv->master) == fpriv->minor->dev->master; +} + +/** + * drm_is_current_master - checks whether @priv is the current master + * @fpriv: DRM file private + * + * Checks whether @fpriv is current master on its device. This decides whether a + * client is allowed to run DRM_MASTER IOCTLs. + * + * Most of the modern IOCTL which require DRM_MASTER are for kernel modesetting + * - the current master is assumed to own the non-shareable display hardware. + */ +bool drm_is_current_master(struct drm_file *fpriv) +{ + bool ret; + + mutex_lock(&fpriv->minor->dev->master_mutex); + ret = drm_is_current_master_locked(fpriv); + mutex_unlock(&fpriv->minor->dev->master_mutex); + + return ret; +} +EXPORT_SYMBOL(drm_is_current_master); + int drm_getmagic(struct drm_device *dev, void *data, struct drm_file *file_priv) { struct drm_auth *auth = data; @@ -223,7 +252,7 @@ int drm_setmaster_ioctl(struct drm_device *dev, void *data, if (ret) goto out_unlock; - if (drm_is_current_master(file_priv)) + if (drm_is_current_master_locked(file_priv)) goto out_unlock; if (dev->master) { @@ -272,7 +301,7 @@ int drm_dropmaster_ioctl(struct drm_device *dev, void *data, if (ret) goto out_unlock; - if (!drm_is_current_master(file_priv)) { + if (!drm_is_current_master_locked(file_priv)) { ret = -EINVAL; goto out_unlock; } @@ -321,7 +350,7 @@ void drm_master_release(struct drm_file *file_priv) if (file_priv->magic) idr_remove(&file_priv->master->magic_map, file_priv->magic); - if (!drm_is_current_master(file_priv)) + if (!drm_is_current_master_locked(file_priv)) goto out; drm_legacy_lock_master_cleanup(dev, master); @@ -342,22 +371,6 @@ void drm_master_release(struct drm_file *file_priv) mutex_unlock(&dev->master_mutex); } -/** - * drm_is_current_master - checks whether @priv is the current master - * @fpriv: DRM file private - * - * Checks whether @fpriv is current master on its device. This decides whether a - * client is allowed to run DRM_MASTER IOCTLs. - * - * Most of the modern IOCTL which require DRM_MASTER are for kernel modesetting - * - the current master is assumed to own the non-shareable display hardware. - */ -bool drm_is_current_master(struct drm_file *fpriv) -{ - return fpriv->is_master && drm_lease_owner(fpriv->master) == fpriv->minor->dev->master; -} -EXPORT_SYMBOL(drm_is_current_master); - /** * drm_master_get - reference a master pointer * @master: &struct drm_master From patchwork Mon Jul 12 04:35:07 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: 12370173 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,URIBL_BLOCKED, 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 98B0CC11F67 for ; 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Sun, 11 Jul 2021 21:36:12 -0700 (PDT) Received: from localhost.localdomain ([118.200.190.93]) by smtp.gmail.com with ESMTPSA id n3sm14242764pfn.216.2021.07.11.21.36.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 11 Jul 2021 21:36:12 -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 v8 4/5] drm: serialize drm_file.master with a new spinlock Date: Mon, 12 Jul 2021 12:35:07 +0800 Message-Id: <20210712043508.11584-5-desmondcheongzx@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210712043508.11584-1-desmondcheongzx@gmail.com> References: <20210712043508.11584-1-desmondcheongzx@gmail.com> MIME-Version: 1.0 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, 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. However, it is not always possible to lock drm_device.master_mutex to dereference drm_file.master. Through the fbdev emulation code, this might occur in a deep nest of other locks. But drm_device.master_mutex is also the outermost lock in the nesting hierarchy, so this leads to potential deadlocks. To address this, we introduce a new spin lock at the bottom of the lock hierarchy that only serializes drm_file.master. With this change, the value of drm_file.master changes only when both drm_device.master_mutex and drm_file.master_lookup_lock are held. Hence, any process holding either of those locks can ensure that the value of drm_file.master will not change concurrently. Since no lock depends on the new drm_file.master_lookup_lock, when drm_file.master is dereferenced, but drm_device.master_mutex cannot be held, we can safely protect the master pointer with drm_file.master_lookup_lock. Reported-by: Daniel Vetter Signed-off-by: Desmond Cheong Zhi Xi --- drivers/gpu/drm/drm_auth.c | 17 +++++++++++------ drivers/gpu/drm/drm_file.c | 1 + include/drm/drm_file.h | 12 +++++++++--- 3 files changed, 21 insertions(+), 9 deletions(-) diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c index ab1863c5a5a0..30a239901b36 100644 --- a/drivers/gpu/drm/drm_auth.c +++ b/drivers/gpu/drm/drm_auth.c @@ -164,16 +164,18 @@ static void drm_set_master(struct drm_device *dev, struct drm_file *fpriv, 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); WARN_ON(fpriv->is_master); old_master = fpriv->master; - fpriv->master = drm_master_create(dev); - if (!fpriv->master) { - fpriv->master = old_master; + new_master = drm_master_create(dev); + if (!new_master) return -ENOMEM; - } + spin_lock(&fpriv->master_lookup_lock); + fpriv->master = new_master; + spin_unlock(&fpriv->master_lookup_lock); fpriv->is_master = 1; fpriv->authenticated = 1; @@ -332,10 +334,13 @@ int drm_master_open(struct drm_file *file_priv) * any master object for render clients */ mutex_lock(&dev->master_mutex); - if (!dev->master) + if (!dev->master) { ret = drm_new_set_master(dev, file_priv); - else + } else { + spin_lock(&file_priv->master_lookup_lock); file_priv->master = drm_master_get(dev->master); + spin_unlock(&file_priv->master_lookup_lock); + } mutex_unlock(&dev->master_mutex); return ret; diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c index d4f0bac6f8f8..ceb1a9723855 100644 --- a/drivers/gpu/drm/drm_file.c +++ b/drivers/gpu/drm/drm_file.c @@ -176,6 +176,7 @@ struct drm_file *drm_file_alloc(struct drm_minor *minor) init_waitqueue_head(&file->event_wait); file->event_space = 4096; /* set aside 4k for event buffer */ + spin_lock_init(&file->master_lookup_lock); mutex_init(&file->event_read_lock); if (drm_core_check_feature(dev, DRIVER_GEM)) diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h index b81b3bfb08c8..9b82988e3427 100644 --- a/include/drm/drm_file.h +++ b/include/drm/drm_file.h @@ -226,15 +226,21 @@ 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, 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. * * See also @authentication and @is_master and the :ref:`section on * primary nodes and authentication `. */ struct drm_master *master; + /** @master_lock: Serializes @master. */ + spinlock_t master_lookup_lock; + /** @pid: Process that opened this file. */ struct pid *pid; From patchwork Mon Jul 12 04:35:08 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: 12370175 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,URIBL_BLOCKED, 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 42A4EC07E99 for ; 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Sun, 11 Jul 2021 21:36:18 -0700 (PDT) Received: from localhost.localdomain ([118.200.190.93]) by smtp.gmail.com with ESMTPSA id n3sm14242764pfn.216.2021.07.11.21.36.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 11 Jul 2021 21:36:18 -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 v8 5/5] drm: protect drm_master pointers in drm_lease.c Date: Mon, 12 Jul 2021 12:35:08 +0800 Message-Id: <20210712043508.11584-6-desmondcheongzx@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210712043508.11584-1-desmondcheongzx@gmail.com> References: <20210712043508.11584-1-desmondcheongzx@gmail.com> MIME-Version: 1.0 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" drm_file->master pointers should be protected by drm_device.master_mutex or drm_file.master_lookup_lock when being dereferenced. However, in drm_lease.c, there are multiple instances where drm_file->master is accessed and dereferenced while neither lock is held. This makes drm_lease.c vulnerable to use-after-free bugs. We address this issue in 2 ways: 1. Add a new drm_file_get_master() function that calls drm_master_get on drm_file->master while holding on to drm_file.master_lookup_lock. Since drm_master_get increments the reference count of master, this prevents master from being freed until we unreference it with drm_master_put. 2. 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 Reviewed-by: Emil Velikov --- drivers/gpu/drm/drm_auth.c | 25 ++++++++++++ drivers/gpu/drm/drm_lease.c | 81 ++++++++++++++++++++++++++++--------- include/drm/drm_auth.h | 1 + include/drm/drm_file.h | 6 +++ 4 files changed, 93 insertions(+), 20 deletions(-) diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c index 30a239901b36..f00354bec3fb 100644 --- a/drivers/gpu/drm/drm_auth.c +++ b/drivers/gpu/drm/drm_auth.c @@ -389,6 +389,31 @@ 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; + + spin_lock(&file_priv->master_lookup_lock); + if (!file_priv->master) + goto unlock; + master = drm_master_get(file_priv->master); + +unlock: + spin_unlock(&file_priv->master_lookup_lock); + 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..92eac73d9001 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) + return true; + ret = _drm_lease_held_master(master, id); + drm_master_put(&master); + + return ret; } /** @@ -128,13 +137,22 @@ 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) + 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); + +out: + drm_master_put(&master); return ret; } @@ -154,10 +172,16 @@ 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) + return crtcs_in; + if (!master->lessor) { + crtcs_out = crtcs_in; + goto out; + } dev = master->dev; count_in = count_out = 0; @@ -176,6 +200,9 @@ 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); + +out: + drm_master_put(&master); return crtcs_out; } @@ -489,7 +516,7 @@ 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 +528,6 @@ 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 +539,22 @@ 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 +565,15 @@ 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 +609,7 @@ 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 +619,8 @@ 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 +643,7 @@ 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 +654,7 @@ 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 +678,7 @@ 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 +698,7 @@ 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 +712,7 @@ 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 +740,7 @@ 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 +759,7 @@ 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 +769,7 @@ 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 +790,7 @@ 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 9b82988e3427..726cfe0ff5f5 100644 --- a/include/drm/drm_file.h +++ b/include/drm/drm_file.h @@ -233,6 +233,12 @@ struct drm_file { * this only matches &drm_device.master if the master is the currently * active one. * + * 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 + * 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 `. */