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=-12.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 C93B0C433DF for ; Thu, 30 Jul 2020 13:24:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B1EFC20829 for ; Thu, 30 Jul 2020 13:24:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728719AbgG3NYS (ORCPT ); Thu, 30 Jul 2020 09:24:18 -0400 Received: from szxga07-in.huawei.com ([45.249.212.35]:56128 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726281AbgG3NYS (ORCPT ); Thu, 30 Jul 2020 09:24:18 -0400 Received: from DGGEMS403-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id A8389BDF52B708896333; Thu, 30 Jul 2020 21:24:09 +0800 (CST) Received: from [127.0.0.1] (10.174.176.211) by DGGEMS403-HUB.china.huawei.com (10.3.19.203) with Microsoft SMTP Server id 14.3.487.0; Thu, 30 Jul 2020 21:24:04 +0800 Subject: Re: [PATCH] vgacon: Fix an out-of-bounds in vgacon_scrollback_update() To: Jiri Slaby , CC: , , , =?UTF-8?B?5byg5LqR5rW3?= References: <20200713105730.550334-1-yangyingliang@huawei.com> <220220f1-48f7-46f6-952f-ab41fa57d6a1@kernel.org> From: Yang Yingliang Message-ID: Date: Thu, 30 Jul 2020 21:24:04 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <220220f1-48f7-46f6-952f-ab41fa57d6a1@kernel.org> Content-Type: text/plain; charset="iso-8859-2"; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Originating-IP: [10.174.176.211] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/7/30 19:04, Jiri Slaby wrote: > On 13. 07. 20, 12:57, Yang Yingliang wrote: >> I got a slab-out-of-bounds report when I doing fuzz test. >> >> [ 334.989515] ================================================================== >> [ 334.989577] BUG: KASAN: slab-out-of-bounds in vgacon_scroll+0x57a/0x8ed >> [ 334.989588] Write of size 1766 at addr ffff8883de69ff3e by task test/2658 >> [ 334.989593] >> [ 334.989608] CPU: 3 PID: 2658 Comm: test Not tainted 5.7.0-rc5-00005-g152036d1379f #789 >> [ 334.989617] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014 >> [ 334.989624] Call Trace: >> [ 334.989646] dump_stack+0xe4/0x14e >> [ 334.989676] print_address_description.constprop.5+0x3f/0x60 >> [ 334.989699] ? vgacon_scroll+0x57a/0x8ed >> [ 334.989710] __kasan_report.cold.8+0x92/0xaf >> [ 334.989735] ? vgacon_scroll+0x57a/0x8ed >> [ 334.989761] kasan_report+0x37/0x50 >> [ 334.989789] check_memory_region+0x1c1/0x1e0 >> [ 334.989806] memcpy+0x38/0x60 >> [ 334.989824] vgacon_scroll+0x57a/0x8ed >> [ 334.989876] con_scroll+0x4ef/0x5e0 > ... >> Because vgacon_scrollback_cur->tail plus memcpy size is greater than >> vgacon_scrollback_cur->size. Fix this by checking the memcpy size. >> >> Reported-by: Hulk Robot >> Signed-off-by: Yang Yingliang >> --- >> drivers/video/console/vgacon.c | 11 ++++++++--- >> 1 file changed, 8 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c >> index 998b0de1812f..b51ffb9a208d 100644 >> --- a/drivers/video/console/vgacon.c >> +++ b/drivers/video/console/vgacon.c >> @@ -243,6 +243,7 @@ static void vgacon_scrollback_startup(void) >> static void vgacon_scrollback_update(struct vc_data *c, int t, int count) >> { >> void *p; >> + int size; >> >> if (!vgacon_scrollback_cur->data || !vgacon_scrollback_cur->size || >> c->vc_num != fg_console) >> @@ -251,13 +252,17 @@ static void vgacon_scrollback_update(struct vc_data *c, int t, int count) >> p = (void *) (c->vc_origin + t * c->vc_size_row); >> >> while (count--) { >> + size = vgacon_scrollback_cur->size - vgacon_scrollback_cur->tail; >> + if (size > c->vc_size_row) >> + size = c->vc_size_row; >> + >> scr_memcpyw(vgacon_scrollback_cur->data + >> vgacon_scrollback_cur->tail, >> - p, c->vc_size_row); >> + p, size); > Are you sure the consumer can handle split lines? As vgacon_scrolldelta > (soff in particular) looks to me like it doesn't. > > Have you tested you patch? I mean with soft scrollback on the vga console? I only test the patch with the reproduce program. Thanks, Yang > >> vgacon_scrollback_cur->cnt++; >> - p += c->vc_size_row; >> - vgacon_scrollback_cur->tail += c->vc_size_row; >> + p += size; >> + vgacon_scrollback_cur->tail += size; >> >> if (vgacon_scrollback_cur->tail >= vgacon_scrollback_cur->size) >> vgacon_scrollback_cur->tail = 0; >> > thanks,