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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 87EAEC433F5 for ; Mon, 4 Oct 2021 13:08:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6A8BA61BC2 for ; Mon, 4 Oct 2021 13:08:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234924AbhJDNKG (ORCPT ); Mon, 4 Oct 2021 09:10:06 -0400 Received: from mail.kernel.org ([198.145.29.99]:38800 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234764AbhJDNGN (ORCPT ); Mon, 4 Oct 2021 09:06:13 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id A7AA961B29; Mon, 4 Oct 2021 13:01:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1633352470; bh=676gQ5WGzDzM5kEVF/NdaXRkrR2WYJaSPaZg6ZhxM0U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=MnYhcN3FO9db3M52+/luNOE/ANhE+CkIpzeFqzfWI5Iw/P3EKneI0VC6iIxnYcNrf onCM8Fw9k7R082VEpAK1+Eu1xpjCimbgb4HgGFHd/CGANo53A/QNNKu+lAfiAeCzK5 XxFifaoMe5UaBAIjN7sC9JaP0TqDxLe6hKdcoN5c= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Igor Matheus Andrade Torrente , Sasha Levin , syzbot+858dc7a2f7ef07c2c219@syzkaller.appspotmail.com Subject: [PATCH 4.14 42/75] tty: Fix out-of-bound vmalloc access in imageblit Date: Mon, 4 Oct 2021 14:52:17 +0200 Message-Id: <20211004125032.928978910@linuxfoundation.org> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20211004125031.530773667@linuxfoundation.org> References: <20211004125031.530773667@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Igor Matheus Andrade Torrente [ Upstream commit 3b0c406124719b625b1aba431659f5cdc24a982c ] This issue happens when a userspace program does an ioctl FBIOPUT_VSCREENINFO passing the fb_var_screeninfo struct containing only the fields xres, yres, and bits_per_pixel with values. If this struct is the same as the previous ioctl, the vc_resize() detects it and doesn't call the resize_screen(), leaving the fb_var_screeninfo incomplete. And this leads to the updatescrollmode() calculates a wrong value to fbcon_display->vrows, which makes the real_y() return a wrong value of y, and that value, eventually, causes the imageblit to access an out-of-bound address value. To solve this issue I made the resize_screen() be called even if the screen does not need any resizing, so it will "fix and fill" the fb_var_screeninfo independently. Cc: stable # after 5.15-rc2 is out, give it time to bake Reported-and-tested-by: syzbot+858dc7a2f7ef07c2c219@syzkaller.appspotmail.com Signed-off-by: Igor Matheus Andrade Torrente Link: https://lore.kernel.org/r/20210628134509.15895-1-igormtorrente@gmail.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/tty/vt/vt.c | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-) diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c index d497208b43f4..f4ac5ec5dc02 100644 --- a/drivers/tty/vt/vt.c +++ b/drivers/tty/vt/vt.c @@ -883,8 +883,25 @@ static int vc_do_resize(struct tty_struct *tty, struct vc_data *vc, new_row_size = new_cols << 1; new_screen_size = new_row_size * new_rows; - if (new_cols == vc->vc_cols && new_rows == vc->vc_rows) - return 0; + if (new_cols == vc->vc_cols && new_rows == vc->vc_rows) { + /* + * This function is being called here to cover the case + * where the userspace calls the FBIOPUT_VSCREENINFO twice, + * passing the same fb_var_screeninfo containing the fields + * yres/xres equal to a number non-multiple of vc_font.height + * and yres_virtual/xres_virtual equal to number lesser than the + * vc_font.height and yres/xres. + * In the second call, the struct fb_var_screeninfo isn't + * being modified by the underlying driver because of the + * if above, and this causes the fbcon_display->vrows to become + * negative and it eventually leads to out-of-bound + * access by the imageblit function. + * To give the correct values to the struct and to not have + * to deal with possible errors from the code below, we call + * the resize_screen here as well. + */ + return resize_screen(vc, new_cols, new_rows, user); + } if (new_screen_size > KMALLOC_MAX_SIZE || !new_screen_size) return -EINVAL; -- 2.33.0