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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 30DDCCD1292 for ; Tue, 9 Apr 2024 02:38:42 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 33A5F10E4E7; Tue, 9 Apr 2024 02:38:41 +0000 (UTC) Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by gabe.freedesktop.org (Postfix) with ESMTPS id B757D10E13A for ; Tue, 9 Apr 2024 02:38:38 +0000 (UTC) Received: from mail.maildlp.com (unknown [172.19.88.105]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4VD97G3C6pztS5S; Tue, 9 Apr 2024 10:35:54 +0800 (CST) Received: from kwepemm600013.china.huawei.com (unknown [7.193.23.68]) by mail.maildlp.com (Postfix) with ESMTPS id 23CA4140124; Tue, 9 Apr 2024 10:38:36 +0800 (CST) Received: from [10.174.178.156] (10.174.178.156) by kwepemm600013.china.huawei.com (7.193.23.68) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.35; Tue, 9 Apr 2024 10:38:35 +0800 Message-ID: Date: Tue, 9 Apr 2024 10:38:34 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.3.2 Subject: Re: [PATCH 4.19.y] drm/vkms: call drm_atomic_helper_shutdown before drm_dev_put() To: Greg KH CC: , , , , References: <20240403094716.80313-1-guomengqi3@huawei.com> <2024040549-pushover-applied-4948@gregkh> From: "guomengqi (A)" In-Reply-To: <2024040549-pushover-applied-4948@gregkh> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.178.156] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To kwepemm600013.china.huawei.com (7.193.23.68) 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: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" 在 2024/4/5 17:30, Greg KH 写道: > On Wed, Apr 03, 2024 at 05:47:16PM +0800, Guo Mengqi wrote: >> commit 73a82b22963d ("drm/atomic: Fix potential use-after-free >> in nonblocking commits") introduced drm_dev_get/put() to >> drm_atomic_helper_shutdown(). And this cause problem in vkms driver exit >> process. >> >> vkms_exit() >> drm_dev_put() >> vkms_release() >> drm_atomic_helper_shutdown() >> drm_dev_get() >> drm_dev_put() >> vkms_release() ------ null pointer access >> >> Using 4.19 stable x86 image on qemu, below stacktrace can be triggered by >> load and unload vkms.ko. >> >> root:~ # insmod vkms.ko >> [ 142.135449] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013). >> [ 142.138713] [drm] Driver supports precise vblank timestamp query. >> [ 142.142390] [drm] Initialized vkms 1.0.0 20180514 for virtual device on minor 0 >> root:~ # rmmod vkms.ko >> [ 144.093710] BUG: unable to handle kernel NULL pointer dereference at 00000000000000a0 >> [ 144.097491] PGD 800000023624e067 P4D 800000023624e067 PUD 22ab59067 PMD 0 >> [ 144.100802] Oops: 0000 [#1] SMP PTI >> [ 144.102502] CPU: 0 PID: 3615 Comm: rmmod Not tainted 4.19.310 #1 >> [ 144.104452] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 >> [ 144.107238] RIP: 0010:device_del+0x34/0x3a0 >> ... >> [ 144.131323] Call Trace: >> [ 144.131962] ? __die+0x7d/0xc0 >> [ 144.132711] ? no_context+0x152/0x3b0 >> [ 144.133605] ? wake_up_q+0x70/0x70 >> [ 144.134436] ? __do_page_fault+0x342/0x4b0 >> [ 144.135445] ? __switch_to_asm+0x41/0x70 >> [ 144.136416] ? __switch_to_asm+0x35/0x70 >> [ 144.137366] ? page_fault+0x1e/0x30 >> [ 144.138214] ? __drm_atomic_state_free+0x51/0x60 >> [ 144.139331] ? device_del+0x34/0x3a0 >> [ 144.140197] platform_device_del.part.14+0x19/0x70 >> [ 144.141348] platform_device_unregister+0xe/0x20 >> [ 144.142458] vkms_release+0x10/0x30 [vkms] >> [ 144.143449] __drm_atomic_helper_disable_all.constprop.31+0x13b/0x150 >> [ 144.144980] drm_atomic_helper_shutdown+0x4b/0x90 >> [ 144.146102] vkms_release+0x18/0x30 [vkms] >> [ 144.147107] vkms_exit+0x29/0x8ec [vkms] >> [ 144.148053] __x64_sys_delete_module+0x155/0x220 >> [ 144.149168] do_syscall_64+0x43/0x100 >> [ 144.150056] entry_SYSCALL_64_after_hwframe+0x5c/0xc1 >> >> It seems that the proper unload sequence is: >> drm_atomic_helper_shutdown(); >> drm_dev_put(); >> >> Just put drm_atomic_helper_shutdown() before drm_dev_put() >> should solve the problem. >> >> Note that vkms exit code is refactored by 53d77aaa3f76 ("drm/vkms: Use >> devm_drm_dev_alloc") in tags/v5.10-rc1. >> >> So this bug only exists on 4.19 and 5.4. > Do we also need this for 5.4? If so, can you send a version for that > tree with the correct Fixes: information, and I will be glad to queue > both of these up. I sent a patch to 5.4.y too. Please check it at https://lore.kernel.org/all/20240409022647.1821-1-guomengqi3@huawei.com/T/#u Thanks, Mengqi > thanks, > > greg k-h > .