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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2B490C11F65 for ; Wed, 30 Jun 2021 14:55:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 063956143B for ; Wed, 30 Jun 2021 14:55:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235585AbhF3O5x (ORCPT ); Wed, 30 Jun 2021 10:57:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60878 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235177AbhF3O5v (ORCPT ); Wed, 30 Jun 2021 10:57:51 -0400 Received: from mail-pf1-x42b.google.com (mail-pf1-x42b.google.com [IPv6:2607:f8b0:4864:20::42b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4D78BC061756; Wed, 30 Jun 2021 07:55:22 -0700 (PDT) Received: by mail-pf1-x42b.google.com with SMTP id a127so2653308pfa.10; Wed, 30 Jun 2021 07:55:22 -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:mime-version :content-transfer-encoding; bh=DbLagrqX9GyFiYDlx5GodYpslzbdCAvx8G0gowIUudY=; b=rnIF81Edc3BhqlLAhT7hsmv4IGJ2tTSllDOEblCmt2DkJCoHAiTvkhLTKVabX/zEIp jVmFNxGLpzqMD79Pwcu+S7EkwFEuzn0yfiy5i1M1TxQD6Io14xq7f1hVfw7ORpo24yXs u9Zx3dPG0dOmI5ovMmchBx9LUXfwLVeiJOTMUsPvr5ax+VfBqaff4BH4Aj35xcqN0pYW dTjvfELHQYsZiJbc+veYEh1PNrZMzYfNa4PqAkJZuJSjGDD1yHsp6ce8uQKoJZG7hVQf Gee2BSaK/VndKuhsqjo+Bh6H+wSDaFmkKZHpePJ+kJdIVhrEIPjzplsJDx3aj6d2DJcR 4JpA== 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:mime-version :content-transfer-encoding; bh=DbLagrqX9GyFiYDlx5GodYpslzbdCAvx8G0gowIUudY=; b=thx6HJ156TsfSKKSKPjLJ/K17n5sZNzgp1gQFPJOz6Te1lVEL0gt7s+gevAPA/mwTn c7psBIHTQEt5FXUORZKq6ar4QckiI2jDL9AtXhOnJRNOiMa8HjyUzLZIw9DApxwYkJq7 rCFQ4b5ti9pqhniXZ42dhT7qb/wPL0BzAFWy3m0pRSjyDgdmmj08UPx3pTUMc9kipCAt oOWYpyTwB9wyyWwQn9Jx5csQ1Mo0vLMnHhEU6DSENnGLlLnwnQMwg1/MA5YKDbMgnVMM 9t5bytQsRGPvNv233YE6173ylzBRv8ok3y7ofhNdC7KEAGRBWsJ/x3MOO4bGFvL9Sz39 axFw== X-Gm-Message-State: AOAM5318Pp24zBlvrYukrYIGXwWMQDG5wFAZP8EDN8E/Hzvt7OxpWzwI i8Ax38OtNlcLtUZDDQxhk1w= X-Google-Smtp-Source: ABdhPJy20ySZ9X53g3XT2CVgt7VxxhHPKHPP85Vof/2Cvj1fsukFMR41XOIOAlZsTMRR6qDi5I1c+A== X-Received: by 2002:a65:608a:: with SMTP id t10mr8423416pgu.311.1625064921816; Wed, 30 Jun 2021 07:55:21 -0700 (PDT) Received: from localhost.localdomain ([118.200.190.93]) by smtp.gmail.com with ESMTPSA id d13sm7157234pjr.49.2021.06.30.07.55.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 30 Jun 2021 07:55:21 -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 Subject: [PATCH v6 0/4] drm: address potential UAF bugs with drm_master ptrs Date: Wed, 30 Jun 2021 22:54:00 +0800 Message-Id: <20210630145404.5958-1-desmondcheongzx@gmail.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This patch series addresses potential use-after-free errors when dereferencing pointers to struct drm_master. These were identified after one such bug was caught by Syzbot in drm_getunique(): https://syzkaller.appspot.com/bug?id=148d2f1dfac64af52ffd27b661981a540724f803 The series is broken up into four patches: 1. Move a call to drm_is_current_master() out from a section locked by &dev->mode_config.mutex in drm_mode_getconnector(). This patch does not apply to stable. 2. Move a call to _drm_lease_held() out from the section locked by &dev->mode_config.idr_mutex in __drm_mode_object_find(). 3. Implement a locked version of drm_is_current_master() function that's used within drm_auth.c. 4. Identify areas in drm_lease.c where pointers to struct drm_master are dereferenced, and ensure that the master pointers are not freed during use. Changes in v5 -> v6: - Patch 2: Add patch 2 to the series. This patch moves the call to _drm_lease_held out from the section locked by &dev->mode_config.idr_mutex in __drm_mode_object_find. - Patch 4: Clarify the kerneldoc for dereferencing drm_file.master, as suggested by Daniel Vetter. Refactor error paths with goto labels so that each function only has a single drm_master_put(), as suggested by Emil Velikov. Modify comparison to NULL into "!master", as suggested by the intel-gfx CI. Changes in v4 -> v5: - Patch 1: Add patch 1 to the series. The changes in patch 1 do not apply to stable because they apply to new changes in the drm-misc-next branch. This patch moves the call to drm_is_current_master in drm_mode_getconnector out from the section locked by &dev->mode_config.mutex. Additionally, added a missing semicolon to the patch, caught by the intel-gfx CI. - Patch 3: Move changes to drm_connector.c into patch 1. Changes in v3 -> v4: - Patch 3: Move the call to drm_is_current_master in drm_mode_getconnector out from the section locked by &dev->mode_config.mutex. As suggested by Daniel Vetter. This avoids a circular lock lock dependency as reported here https://patchwork.freedesktop.org/patch/440406/ Additionally, inside drm_is_current_master, instead of grabbing &fpriv->master->dev->master_mutex, we grab &fpriv->minor->dev->master_mutex to avoid dereferencing a null ptr if fpriv->master is not set. - Patch 4: Modify kerneldoc formatting. Additionally, add a file_priv->master NULL check inside drm_file_get_master, and handle the NULL result accordingly in drm_lease.c. As suggested by Daniel Vetter. Changes in v2 -> v3: - Patch 3: Move the definition of drm_is_current_master and the _locked version higher up in drm_auth.c to avoid needing a forward declaration of drm_is_current_master_locked. As suggested by Daniel Vetter. - Patch 4: Instead of leaking drm_device.master_mutex into drm_lease.c to protect drm_master pointers, add a new drm_file_get_master() function that returns drm_file->master while increasing its reference count, to prevent drm_file->master from being freed. As suggested by Daniel Vetter. Changes in v1 -> v2: - Patch 4: Move the lock and assignment before the DRM_DEBUG_LEASE in drm_mode_get_lease_ioctl, as suggested by Emil Velikov. Desmond Cheong Zhi Xi (4): drm: avoid circular locks in drm_mode_getconnector drm: avoid circular locks in __drm_mode_object_find drm: add a locked version of drm_is_current_master drm: protect drm_master pointers in drm_lease.c drivers/gpu/drm/drm_auth.c | 76 +++++++++++++++++++++-------- drivers/gpu/drm/drm_connector.c | 5 +- drivers/gpu/drm/drm_lease.c | 81 +++++++++++++++++++++++-------- drivers/gpu/drm/drm_mode_object.c | 10 ++-- include/drm/drm_auth.h | 1 + include/drm/drm_file.h | 15 ++++-- 6 files changed, 141 insertions(+), 47 deletions(-) -- 2.25.1