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=-16.8 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,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 1D4B6C432BE for ; Thu, 19 Aug 2021 05:32:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ECF6761152 for ; Thu, 19 Aug 2021 05:32:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230081AbhHSFce (ORCPT ); Thu, 19 Aug 2021 01:32:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59478 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229868AbhHSFcd (ORCPT ); Thu, 19 Aug 2021 01:32:33 -0400 Received: from mail-pl1-x634.google.com (mail-pl1-x634.google.com [IPv6:2607:f8b0:4864:20::634]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 253C2C061756; Wed, 18 Aug 2021 22:31:58 -0700 (PDT) Received: by mail-pl1-x634.google.com with SMTP id n12so3261026plf.4; Wed, 18 Aug 2021 22:31:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:subject:to:cc:references:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=CFAh2ohJN76u6Eruh33dHQq9ass8KChMC1IajJFgPH8=; b=HYJgzpgvWaAw7btZx7v+sX1ebqDpXWCM6m12POBpIsuzItZ06SvUkJuPbKSrk3FuUc oamxPO8fPNZoUWWvVhUe6rkiV+DYt4vrGo9UKMbe/DJzyAfx8pVYL9oT7wzEDEaT/S91 MmLakU9Uc62a1+VqiSNx91xei08VB93GtjMoJBPhYeX1dBjzDD3H5aGUw6MbhZ1YAJMp edbzJMAQUCan7g7Pb4YcfY8ahN+yNPwK2RvCSSwdgqkVqiEWtb0r94XSsLROR+zdX6oL +zvE2OvSSn57qPUP3aFejiG5nF2zHujYVVjjWPVvVKzuYc/oIodXR+Uo9xiPffPqY+S6 3eMw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:subject:to:cc:references:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=CFAh2ohJN76u6Eruh33dHQq9ass8KChMC1IajJFgPH8=; b=AA3evgJ+VsWOiuBeOY2Eqbpmzv3ALON7eK90DjqPbPOXJG/USUDj8CgUo3InicINMT yElv3JJ6abqRcusfUb/ol2tVnWXTo2iyH4ZkzUrhzNeWExEDWTqWi9W85qcFum26lHGW 9PrIZFbaYzR1DNN9DNTyU5ikbbnED2nSxe7EHjDAbCBDpKpu03nSIer9/wwMabMuhCoF 4iFBmldcm7ToqENztW0nTAtwtmtch/lhGHpGFRcQwCsxv7s1vfHW5rZK2M+ug2pTtp6O IFU+ZSSeemm0O865N2IVHEr5XGplX59XY5xIRyJGZxZE0VJxdc19l/8PRoqOk3NuOWBN iP8w== X-Gm-Message-State: AOAM532duE2YbW2SlmwLw87A7eWCJqk5SZ0eqG+ARfhRob0u/IeyBz/x 9ZRx6SxTAkrBqO583j55iX8= X-Google-Smtp-Source: ABdhPJzHWe7IqBDZJBR5DhOXYwVbuf1qus5KD/vagYpAW2JTmvesSwzD7dXboeZyB3QuDoSce3EDfQ== X-Received: by 2002:a17:90a:9f91:: with SMTP id o17mr12909893pjp.29.1629351117654; Wed, 18 Aug 2021 22:31:57 -0700 (PDT) Received: from [192.168.1.237] ([118.200.190.93]) by smtp.gmail.com with ESMTPSA id s26sm1873118pgv.46.2021.08.18.22.31.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 18 Aug 2021 22:31:57 -0700 (PDT) From: Desmond Cheong Zhi Xi Subject: Re: [Intel-gfx] [PATCH v3 4/9] drm: fix potential null ptr dereferences in drm_{auth, ioctl} To: Daniel Vetter Cc: Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Dave Airlie , Sumit Semwal , =?UTF-8?Q?Christian_K=c3=b6nig?= , Jens Axboe , Oleg Nesterov , Thomas Gleixner , Dmitry Vyukov , walter-zh.wu@mediatek.com, dri-devel , Linux Kernel Mailing List , intel-gfx , "open list:DMA BUFFER SHARING FRAMEWORK" , "moderated list:DMA BUFFER SHARING FRAMEWORK" , Shuah Khan , Greg KH , linux-kernel-mentees@lists.linuxfoundation.org References: <20210818073824.1560124-1-desmondcheongzx@gmail.com> <20210818073824.1560124-5-desmondcheongzx@gmail.com> <53a63ac8-f2de-91f7-4e0f-20b0f3f61d52@gmail.com> Message-ID: <18df91cb-3948-f4f4-d548-8d23107540ae@gmail.com> Date: Thu, 19 Aug 2021 13:31:51 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 19/8/21 12:33 am, Daniel Vetter wrote: > On Wed, Aug 18, 2021 at 5:37 PM Desmond Cheong Zhi Xi > wrote: >> >> On 18/8/21 6:11 pm, Daniel Vetter wrote: >>> On Wed, Aug 18, 2021 at 03:38:19PM +0800, Desmond Cheong Zhi Xi wrote: >>>> There are three areas where we dereference struct drm_master without >>>> checking if the pointer is non-NULL. >>>> >>>> 1. drm_getmagic is called from the ioctl_handler. Since >>>> DRM_IOCTL_GET_MAGIC has no ioctl flags, drm_getmagic is run without >>>> any check that drm_file.master has been set. >>>> >>>> 2. Similarly, drm_getunique is called from the ioctl_handler, but >>>> DRM_IOCTL_GET_UNIQUE has no ioctl flags. So there is no guarantee that >>>> drm_file.master has been set. >>> >>> I think the above two are impossible, due to the refcounting rules for >>> struct file. >>> >> >> Right, will drop those two parts from the patch. >> >>>> 3. drm_master_release can also be called without having a >>>> drm_file.master set. Here is one error path: >>>> drm_open(): >>>> drm_open_helper(): >>>> drm_master_open(): >>>> drm_new_set_master(); <--- returns -ENOMEM, >>>> drm_file.master not set >>>> drm_file_free(): >>>> drm_master_release(); <--- NULL ptr dereference >>>> (file_priv->master->magic_map) >>>> >>>> Fix these by checking if the master pointers are NULL before use. >>>> >>>> Signed-off-by: Desmond Cheong Zhi Xi >>>> --- >>>> drivers/gpu/drm/drm_auth.c | 16 ++++++++++++++-- >>>> drivers/gpu/drm/drm_ioctl.c | 5 +++++ >>>> 2 files changed, 19 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c >>>> index f9267b21556e..b7230604496b 100644 >>>> --- a/drivers/gpu/drm/drm_auth.c >>>> +++ b/drivers/gpu/drm/drm_auth.c >>>> @@ -95,11 +95,18 @@ 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; >>>> + struct drm_master *master; >>>> int ret = 0; >>>> >>>> mutex_lock(&dev->master_mutex); >>>> + master = file_priv->master; >>>> + if (!master) { >>>> + mutex_unlock(&dev->master_mutex); >>>> + return -EINVAL; >>>> + } >>>> + >>>> if (!file_priv->magic) { >>>> - ret = idr_alloc(&file_priv->master->magic_map, file_priv, >>>> + ret = idr_alloc(&master->magic_map, file_priv, >>>> 1, 0, GFP_KERNEL); >>>> if (ret >= 0) >>>> file_priv->magic = ret; >>>> @@ -355,8 +362,12 @@ void drm_master_release(struct drm_file *file_priv) >>>> >>>> mutex_lock(&dev->master_mutex); >>>> master = file_priv->master; >>>> + >>>> + if (!master) >>>> + goto unlock; >>> >>> This is a bit convoluted, since we're in the single-threaded release path >>> we don't need any locking for file_priv related things. Therefore we can >>> pull the master check out and just directly return. >>> >>> But since it's a bit surprising maybe a comment that this can happen when >>> drm_master_open in drm_open_helper fails? >>> >> >> Sounds good. This can actually also happen in the failure path of >> mock_drm_getfile if anon_inode_getfile fails. I'll leave a short note >> about both of them. >> >>> Another option, and maybe cleaner, would be to move the drm_master_release >>> from drm_file_free into drm_close_helper. That would be fully symmetrical >>> and should also fix the bug here? >>> -Daniel >>> >> Hmmm maybe the first option to move the check out of the lock might be >> better. If I'm not wrong, we would otherwise also need to move >> drm_master_release into drm_client_close. > > Do we have to? > > If I haven't missed anything, the drm_client stuff only calls > drm_file_alloc and doesn't set up a master. So this should work? > -Daniel > Ahhhh ok yes, I understand what's going on better now. I think you're right, moving drm_master_release into drm_close_helper should fix all the places it can go wrong. >> >>> >>>> + >>>> if (file_priv->magic) >>>> - idr_remove(&file_priv->master->magic_map, file_priv->magic); >>>> + idr_remove(&master->magic_map, file_priv->magic); >>>> >>>> if (!drm_is_current_master_locked(file_priv)) >>>> goto out; >>>> @@ -379,6 +390,7 @@ void drm_master_release(struct drm_file *file_priv) >>>> drm_master_put(&file_priv->master); >>>> spin_unlock(&dev->master_lookup_lock); >>>> } >>>> +unlock: >>>> mutex_unlock(&dev->master_mutex); >>>> } >>>> >>>> diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c >>>> index 26f3a9ede8fe..4d029d3061d9 100644 >>>> --- a/drivers/gpu/drm/drm_ioctl.c >>>> +++ b/drivers/gpu/drm/drm_ioctl.c >>>> @@ -121,6 +121,11 @@ int drm_getunique(struct drm_device *dev, void *data, >>>> >>>> mutex_lock(&dev->master_mutex); >>>> master = file_priv->master; >>>> + if (!master) { >>>> + mutex_unlock(&dev->master_mutex); >>>> + return -EINVAL; >>>> + } >>>> + >>>> if (u->unique_len >= master->unique_len) { >>>> if (copy_to_user(u->unique, master->unique, master->unique_len)) { >>>> mutex_unlock(&dev->master_mutex); >>>> -- >>>> 2.25.1 >>>> >>> >> > >