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=-16.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 B62BBC07E94 for ; Fri, 4 Jun 2021 13:20:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 92EF4613E7 for ; Fri, 4 Jun 2021 13:20:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230220AbhFDNVv (ORCPT ); Fri, 4 Jun 2021 09:21:51 -0400 Received: from mail.kernel.org ([198.145.29.99]:52118 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230004AbhFDNVu (ORCPT ); Fri, 4 Jun 2021 09:21:50 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 794E9613DE; Fri, 4 Jun 2021 13:19:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1622812791; bh=74LOlmBA6nBCcsHqoSpsW9MYDwdS4flEvJZPaEiNQvs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=dNq4z+EpVvlKKvWtNTK0R1a1VEAMZNR5HJygxiMwTj3jISUpAxMzF8KTlTlHuzsbk ucBTJG6KTRxhvtqtwb9IO5z1QSYL+jrQUWRQ1Bga4rKWdrsSmeN0TZf/OQSEL+SKJZ jgneCliXk3GIBSNDqicXaNbOIOArLJhZceCfjbho= Date: Fri, 4 Jun 2021 15:19:43 +0200 From: Greg KH To: Igor Matheus Andrade Torrente Cc: jirislaby@kernel.org, linux-kernel@vger.kernel.org, syzbot+858dc7a2f7ef07c2c219@syzkaller.appspotmail.com Subject: Re: [PATCH RFC] tty: Fix out-of-bound vmalloc access in imageblit Message-ID: References: <20210531124713.9048-1-igormtorrente@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210531124713.9048-1-igormtorrente@gmail.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 31, 2021 at 09:47:13AM -0300, Igor Matheus Andrade Torrente wrote: > 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 brougth the resize_screen() the > beginning of vc_do_resize(), so it will "fix and fill" > the fb_var_screeninfo even if the screen does not need any > resizing. > > Reported-and-tested-by: syzbot+858dc7a2f7ef07c2c219@syzkaller.appspotmail.com > Signed-off-by: Igor Matheus Andrade Torrente > --- > drivers/tty/vt/vt.c | 12 ++++-------- > 1 file changed, 4 insertions(+), 8 deletions(-) > > diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c > index fa1548d4f94b..1b90758d8893 100644 > --- a/drivers/tty/vt/vt.c > +++ b/drivers/tty/vt/vt.c > @@ -1219,6 +1219,10 @@ 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; > > + err = resize_screen(vc, new_cols, new_rows, user); > + if (err) > + return err; > + > if (new_cols == vc->vc_cols && new_rows == vc->vc_rows) > return 0; > But now if any of the checks below this call fail, the screen will be resized and not "put back" to the original size, right? That could cause a mis-match of what is expected here. thanks, greg k-h