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 1112EC48BDF for ; Thu, 24 Jun 2021 12:57:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D4865613F9 for ; Thu, 24 Jun 2021 12:57:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231626AbhFXNAE (ORCPT ); Thu, 24 Jun 2021 09:00:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:44794 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229995AbhFXNAB (ORCPT ); Thu, 24 Jun 2021 09:00:01 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 38793613C3; Thu, 24 Jun 2021 12:57:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1624539461; bh=HjaVdHowmGn+bxqs/WsvX1B9BQgWJs+HkHjrRTRg8Og=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=vi+R578DRyMLSh7YeVvlf8/MfgXWcvIHagCrJTwLTw/5gn5iRFjvk22tRaan2cfIP NlzEh4YvosgFBuI20+wDNMXzbXVc84sJDt7sY81h7zVoVYa8v1vzXksLF2CCAmP3nt 9bo9T1EsRRY4G0e6YoZSw2Pu2uV0kyRbwWRxYTvg= Date: Thu, 24 Jun 2021 14:57:39 +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 v3] tty: Fix out-of-bound vmalloc access in imageblit Message-ID: References: <20210617223720.29378-1-igormtorrente@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210617223720.29378-1-igormtorrente@gmail.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 17, 2021 at 07:37:20PM -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 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. > > Reported-and-tested-by: syzbot+858dc7a2f7ef07c2c219@syzkaller.appspotmail.com > Signed-off-by: Igor Matheus Andrade Torrente > --- > v2: It Tries to avoid the problem found by Greg in the previous > patch. > > v3: Add a big comment explaining why this is being done the way > it is. > --- > drivers/tty/vt/vt.c | 15 ++++++++++++++- > 1 file changed, 14 insertions(+), 1 deletion(-) > > diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c > index fa1548d4f94b..a0207525a945 100644 > --- a/drivers/tty/vt/vt.c > +++ b/drivers/tty/vt/vt.c > @@ -1220,7 +1220,20 @@ static int vc_do_resize(struct tty_struct *tty, struct vc_data *vc, > new_screen_size = new_row_size * new_rows; > > if (new_cols == vc->vc_cols && new_rows == vc->vc_rows) > - return 0; > + /* This function is being called here to cover the case Please do not use networking style comments, use normal ones: /* * This function... > + * where the userspace calls the FBIOPUT_VSCREENINFO twice, > + * passing the same fb_var_screeninfo containing only the > + * fields xres, yres, and bits_per_pixel with yeird(but valid) "yeird"? And put a space after that word please. thanks, greg k-h