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=-14.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,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 DAFC4C433E1 for ; Tue, 18 Aug 2020 11:18:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B8BA120706 for ; Tue, 18 Aug 2020 11:18:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597749494; bh=Z0Hf+Sc1zOZUK1D1KvwLRzc2mHhpVOafjsndOkMkvJk=; h=Subject:To:From:Date:List-ID:From; b=nohdFNo08RkQKsbILbvfwnz1ThfPHEw1kzMDIaEc5yy63JsDTXD9onSsorV+bDh6U m0xvh4U+yWCY1uw/p+yp1erWrh7bZuUh2TdD4od+roN43Jptrz+srqWR4zzu/e9dmM sZeF8k+XKQaPSmfgv5fZ/PcJ2driTb53MRNpsipw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726203AbgHRLSL (ORCPT ); Tue, 18 Aug 2020 07:18:11 -0400 Received: from mail.kernel.org ([198.145.29.99]:40102 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726145AbgHRLSJ (ORCPT ); Tue, 18 Aug 2020 07:18:09 -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 4BAC520706; Tue, 18 Aug 2020 11:18:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597749488; bh=Z0Hf+Sc1zOZUK1D1KvwLRzc2mHhpVOafjsndOkMkvJk=; h=Subject:To:From:Date:From; b=xnUcyNLuVRCkCEcPEAAHTJwBEnJq7JQ+ovf3fDPSGojJxCoTdO4ulBzfPzNF3rJbk bksFC0ddzg8YcPCiiItTwpBucFKyPt/i6H700VxEeUujzZYvQsEf7oSbWHylOeI5u/ keX4fv7JDLwMlmUIOryWQ31XNgJwWVwXYIydYv6U= Subject: patch "vt: defer kfree() of vc_screenbuf in vc_do_resize()" added to tty-linus To: penguin-kernel@I-love.SAKURA.ne.jp, gregkh@linuxfoundation.org, stable@vger.kernel.org, syzbot+9116ecc1978ca3a12f43@syzkaller.appspotmail.com From: Date: Tue, 18 Aug 2020 13:18:31 +0200 Message-ID: <1597749511891@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org This is a note to let you know that I've just added the patch titled vt: defer kfree() of vc_screenbuf in vc_do_resize() to my tty git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git in the tty-linus branch. The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.) The patch will hopefully also be merged in Linus's tree for the next -rc kernel release. If you have any questions about this process, please let me know. >From f8d1653daec02315e06d30246cff4af72e76e54e Mon Sep 17 00:00:00 2001 From: Tetsuo Handa Date: Wed, 29 Jul 2020 23:57:01 +0900 Subject: vt: defer kfree() of vc_screenbuf in vc_do_resize() syzbot is reporting UAF bug in set_origin() from vc_do_resize() [1], for vc_do_resize() calls kfree(vc->vc_screenbuf) before calling set_origin(). Unfortunately, in set_origin(), vc->vc_sw->con_set_origin() might access vc->vc_pos when scroll is involved in order to manipulate cursor, but vc->vc_pos refers already released vc->vc_screenbuf until vc->vc_pos gets updated based on the result of vc->vc_sw->con_set_origin(). Preserving old buffer and tolerating outdated vc members until set_origin() completes would be easier than preventing vc->vc_sw->con_set_origin() from accessing outdated vc members. [1] https://syzkaller.appspot.com/bug?id=6649da2081e2ebdc65c0642c214b27fe91099db3 Reported-by: syzbot Signed-off-by: Tetsuo Handa Cc: stable Link: https://lore.kernel.org/r/1596034621-4714-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp Signed-off-by: Greg Kroah-Hartman --- drivers/tty/vt/vt.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c index ccb533fd00a2..a4f08c0da84b 100644 --- a/drivers/tty/vt/vt.c +++ b/drivers/tty/vt/vt.c @@ -1201,7 +1201,7 @@ static int vc_do_resize(struct tty_struct *tty, struct vc_data *vc, unsigned int old_rows, old_row_size, first_copied_row; unsigned int new_cols, new_rows, new_row_size, new_screen_size; unsigned int user; - unsigned short *newscreen; + unsigned short *oldscreen, *newscreen; struct uni_screen *new_uniscr = NULL; WARN_CONSOLE_UNLOCKED(); @@ -1299,10 +1299,11 @@ static int vc_do_resize(struct tty_struct *tty, struct vc_data *vc, if (new_scr_end > new_origin) scr_memsetw((void *)new_origin, vc->vc_video_erase_char, new_scr_end - new_origin); - kfree(vc->vc_screenbuf); + oldscreen = vc->vc_screenbuf; vc->vc_screenbuf = newscreen; vc->vc_screenbuf_size = new_screen_size; set_origin(vc); + kfree(oldscreen); /* do part of a reset_terminal() */ vc->vc_top = 0; -- 2.28.0