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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 12633C10F27 for ; Tue, 10 Mar 2020 13:35:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E071D20675 for ; Tue, 10 Mar 2020 13:35:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583847354; bh=tI5Cf/9BQhu3bM0yslg1rfjjrkLMj5K6gxj4++CS5/k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=BxR8oWbiyfkZuxvfaAVGBmp5gjWPnN74IjTpk/IiBCSgjyNZqKNxzFerEMZXuArMW ljfNlITUuUQl0MEZYCq1W/uTsoxHvEnNL5p7p2/HnlIDRrx+jDP3/6fIeoDgznVF0f bPxLdekkPh7YsXZHuCfu/w5zTFTioZAm+8NSRNAc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727616AbgCJMnj (ORCPT ); Tue, 10 Mar 2020 08:43:39 -0400 Received: from mail.kernel.org ([198.145.29.99]:43982 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727609AbgCJMng (ORCPT ); Tue, 10 Mar 2020 08:43:36 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B3C1824693; Tue, 10 Mar 2020 12:43:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583844215; bh=tI5Cf/9BQhu3bM0yslg1rfjjrkLMj5K6gxj4++CS5/k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NwewYP0LBPIxTUEv6MHxmymE+VjZG7jiIADhABhMMjs/s9jF/kfC/9jy0u/MTHD1W wtxXqLgR3YgJKTfMGziVoiFUW+X95NxdAFXpZG7PHPcFUNNYrReTVNVwHsf/b2Jnuz U7ki3/6i7ybaKAATmaEWK+Uch01ER5Gna3IZBbVg= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Hulk Robot , Zhang Xiaoxu , Daniel Vetter Subject: [PATCH 4.4 55/72] vgacon: Fix a UAF in vgacon_invert_region Date: Tue, 10 Mar 2020 13:39:08 +0100 Message-Id: <20200310123614.912840674@linuxfoundation.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200310123601.053680753@linuxfoundation.org> References: <20200310123601.053680753@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Zhang Xiaoxu commit 513dc792d6060d5ef572e43852683097a8420f56 upstream. When syzkaller tests, there is a UAF: BUG: KASan: use after free in vgacon_invert_region+0x9d/0x110 at addr ffff880000100000 Read of size 2 by task syz-executor.1/16489 page:ffffea0000004000 count:0 mapcount:-127 mapping: (null) index:0x0 page flags: 0xfffff00000000() page dumped because: kasan: bad access detected CPU: 1 PID: 16489 Comm: syz-executor.1 Not tainted Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.3-0-ge2fc41e-prebuilt.qemu-project.org 04/01/2014 Call Trace: [] dump_stack+0x1e/0x20 [] kasan_report+0x577/0x950 [] __asan_load2+0x62/0x80 [] vgacon_invert_region+0x9d/0x110 [] invert_screen+0xe5/0x470 [] set_selection+0x44b/0x12f0 [] tioclinux+0xee/0x490 [] vt_ioctl+0xff4/0x2670 [] tty_ioctl+0x46a/0x1a10 [] do_vfs_ioctl+0x5bd/0xc40 [] SyS_ioctl+0x132/0x170 [] system_call_fastpath+0x22/0x27 Memory state around the buggy address: ffff8800000fff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff8800000fff80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >ffff880000100000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff It can be reproduce in the linux mainline by the program: #include #include #include #include #include #include #include #include struct tiocl_selection { unsigned short xs; /* X start */ unsigned short ys; /* Y start */ unsigned short xe; /* X end */ unsigned short ye; /* Y end */ unsigned short sel_mode; /* selection mode */ }; #define TIOCL_SETSEL 2 struct tiocl { unsigned char type; unsigned char pad; struct tiocl_selection sel; }; int main() { int fd = 0; const char *dev = "/dev/char/4:1"; struct vt_consize v = {0}; struct tiocl tioc = {0}; fd = open(dev, O_RDWR, 0); v.v_rows = 3346; ioctl(fd, VT_RESIZEX, &v); tioc.type = TIOCL_SETSEL; ioctl(fd, TIOCLINUX, &tioc); return 0; } When resize the screen, update the 'vc->vc_size_row' to the new_row_size, but when 'set_origin' in 'vgacon_set_origin', vgacon use 'vga_vram_base' for 'vc_origin' and 'vc_visible_origin', not 'vc_screenbuf'. It maybe smaller than 'vc_screenbuf'. When TIOCLINUX, use the new_row_size to calc the offset, it maybe larger than the vga_vram_size in vgacon driver, then bad access. Also, if set an larger screenbuf firstly, then set an more larger screenbuf, when copy old_origin to new_origin, a bad access may happen. So, If the screen size larger than vga_vram, resize screen should be failed. This alse fix CVE-2020-8649 and CVE-2020-8647. Linus pointed out that overflow checking seems absent. We're saved by the existing bounds checks in vc_do_resize() with rather strict limits: if (cols > VC_RESIZE_MAXCOL || lines > VC_RESIZE_MAXROW) return -EINVAL; Fixes: 0aec4867dca14 ("[PATCH] SVGATextMode fix") Reference: CVE-2020-8647 and CVE-2020-8649 Reported-by: Hulk Robot Signed-off-by: Zhang Xiaoxu [danvet: augment commit message to point out overflow safety] Cc: stable@vger.kernel.org Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20200304022429.37738-1-zhangxiaoxu5@huawei.com Signed-off-by: Greg Kroah-Hartman --- drivers/video/console/vgacon.c | 3 +++ 1 file changed, 3 insertions(+) --- a/drivers/video/console/vgacon.c +++ b/drivers/video/console/vgacon.c @@ -1330,6 +1330,9 @@ static int vgacon_font_get(struct vc_dat static int vgacon_resize(struct vc_data *c, unsigned int width, unsigned int height, unsigned int user) { + if ((width << 1) * height > vga_vram_size) + return -EINVAL; + if (width % 2 || width > screen_info.orig_video_cols || height > (screen_info.orig_video_lines * vga_default_font_height)/ c->vc_font.height)