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 2DFA6C55179 for ; Wed, 28 Oct 2020 22:17:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D9C2F206D4 for ; Wed, 28 Oct 2020 22:17:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603923457; bh=HpHXGfQ/NrqF+O5uHqaq7ANAiD3lIN5bPX+OZQwGWOw=; h=Subject:To:From:Date:List-ID:From; b=DwJpNW8CLQIJ557Atras+eMVrteWo1/OhXtdYCg5EJnvnGzPmNpXaaMndsLEiL/9u q47WCDDBurnmIdG3Ti8f4biF9Y6w2WLBM1JtsWzYQNgghFa46qqPkck924IPrBB3hP aBMP/NeAjZFD7ITvAXVci9EEBOkkKlKoOboeN7mY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731620AbgJ1WRg (ORCPT ); Wed, 28 Oct 2020 18:17:36 -0400 Received: from mail.kernel.org ([198.145.29.99]:60514 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731589AbgJ1WRd (ORCPT ); Wed, 28 Oct 2020 18:17:33 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (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 D3A3F24735; Wed, 28 Oct 2020 12:41:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603888906; bh=HpHXGfQ/NrqF+O5uHqaq7ANAiD3lIN5bPX+OZQwGWOw=; h=Subject:To:From:Date:From; b=V54s1174TaNxYKmXX4I1hy3yWaHZhakat1KXaIryR7meLQUMYLcGlhnT3KaiKbnw3 d+9gbStMqWe28em7YpZKp3WkxBdXNAa1Se4syUVD8Gxi5HD8MRf8eK87h0Yi9DtoyN G0/rE3HXU7nHVUKbhAYH7GpUjWC7CCukeXrwjxYw= Subject: patch "vt: keyboard, extend func_buf_lock to readers" added to tty-linus To: jslaby@suse.cz, gregkh@linuxfoundation.org, stable@vger.kernel.org, yuanmingbuaa@gmail.com From: Date: Wed, 28 Oct 2020 13:42:30 +0100 Message-ID: <160388895048113@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit 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: keyboard, extend func_buf_lock to readers 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 82e61c3909db51d91b9d3e2071557b6435018b80 Mon Sep 17 00:00:00 2001 From: Jiri Slaby Date: Mon, 19 Oct 2020 10:55:17 +0200 Subject: vt: keyboard, extend func_buf_lock to readers Both read-side users of func_table/func_buf need locking. Without that, one can easily confuse the code by repeatedly setting altering strings like: while (1) for (a = 0; a < 2; a++) { struct kbsentry kbs = {}; strcpy((char *)kbs.kb_string, a ? ".\n" : "88888\n"); ioctl(fd, KDSKBSENT, &kbs); } When that program runs, one can get unexpected output by holding F1 (note the unxpected period on the last line): . 88888 .8888 So protect all accesses to 'func_table' (and func_buf) by preexisting 'func_buf_lock'. It is easy in 'k_fn' handler as 'puts_queue' is expected not to sleep. On the other hand, KDGKBSENT needs a local (atomic) copy of the string because copy_to_user can sleep. Use already allocated, but unused 'kbs->kb_string' for that purpose. Note that the program above needs at least CAP_SYS_TTY_CONFIG. This depends on the previous patch and on the func_buf_lock lock added in commit 46ca3f735f34 (tty/vt: fix write/write race in ioctl(KDSKBSENT) handler) in 5.2. Likely fixes CVE-2020-25656. Cc: Reported-by: Minh Yuan Signed-off-by: Jiri Slaby Link: https://lore.kernel.org/r/20201019085517.10176-2-jslaby@suse.cz Signed-off-by: Greg Kroah-Hartman --- drivers/tty/vt/keyboard.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) diff --git a/drivers/tty/vt/keyboard.c b/drivers/tty/vt/keyboard.c index 7bfa95c3252c..78acc270e39a 100644 --- a/drivers/tty/vt/keyboard.c +++ b/drivers/tty/vt/keyboard.c @@ -743,8 +743,13 @@ static void k_fn(struct vc_data *vc, unsigned char value, char up_flag) return; if ((unsigned)value < ARRAY_SIZE(func_table)) { + unsigned long flags; + + spin_lock_irqsave(&func_buf_lock, flags); if (func_table[value]) puts_queue(vc, func_table[value]); + spin_unlock_irqrestore(&func_buf_lock, flags); + } else pr_err("k_fn called with value=%d\n", value); } @@ -1991,7 +1996,7 @@ int vt_do_kdsk_ioctl(int cmd, struct kbentry __user *user_kbe, int perm, #undef s #undef v -/* FIXME: This one needs untangling and locking */ +/* FIXME: This one needs untangling */ int vt_do_kdgkb_ioctl(int cmd, struct kbsentry __user *user_kdgkb, int perm) { struct kbsentry *kbs; @@ -2023,10 +2028,14 @@ int vt_do_kdgkb_ioctl(int cmd, struct kbsentry __user *user_kdgkb, int perm) switch (cmd) { case KDGKBSENT: { /* size should have been a struct member */ - unsigned char *from = func_table[i] ? : ""; + ssize_t len = sizeof(user_kdgkb->kb_string); + + spin_lock_irqsave(&func_buf_lock, flags); + len = strlcpy(kbs->kb_string, func_table[i] ? : "", len); + spin_unlock_irqrestore(&func_buf_lock, flags); - ret = copy_to_user(user_kdgkb->kb_string, from, - strlen(from) + 1) ? -EFAULT : 0; + ret = copy_to_user(user_kdgkb->kb_string, kbs->kb_string, + len + 1) ? -EFAULT : 0; goto reterr; } -- 2.29.1