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=-6.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS 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 9A614C433DF for ; Mon, 25 May 2020 23:29:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 720E12071A for ; Mon, 25 May 2020 23:29:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="flg9K9go" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729342AbgEYX3o (ORCPT ); Mon, 25 May 2020 19:29:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47256 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726408AbgEYX3o (ORCPT ); Mon, 25 May 2020 19:29:44 -0400 Received: from mail-pg1-x544.google.com (mail-pg1-x544.google.com [IPv6:2607:f8b0:4864:20::544]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 07BB3C061A0E for ; Mon, 25 May 2020 16:29:44 -0700 (PDT) Received: by mail-pg1-x544.google.com with SMTP id w20so4143651pga.6 for ; Mon, 25 May 2020 16:29:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=HtNezEclsV3pjj2sk3NG9HBDY2EhLkx6eltEU65OOyE=; b=flg9K9goUWDX1Mx2Rti/3IaC4zT5n8y/FrPVkiRBFnPbS2Myt7FIrm1Cu8Pf7lV1VL +HpLlwb0ocH+0cO+k7Oyjq34X5obQ0G0vS8d5uHDlL+VZ6NNJg270ltVqamYPVOOkmSL TkwYwURwmbaCUe7C8NcAlrAePX6h6trhKd9a9z4Pcx91He4lMqmqPT51dkEv2aIY4Fui WH6of9yOwdUj3VVsIxc+QF0dUVLzex1HlPmQlc7y2PaHOFt6Q85TwhZTzxobCbGbG9Vp hrhjgQAgTdGLpHA3UyvtqA7MtA1iDrBp8Xuu2y9HpwUOZ7BP90a4tmAiPs8n9jTVIYe7 JC6A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=HtNezEclsV3pjj2sk3NG9HBDY2EhLkx6eltEU65OOyE=; b=JscsJmqZqB4/axE0TbHcE80TPBZs2b8p/vgHqgHYNBCIAAw3emQyxBX0slmnp+JH/a LMZA3UrZ/lEM7q0pHlh5GyH6QzEae6lFZXWx+biMPDyzQSAnNLD++FzvHeynCMMw9jz/ H1/JnC2v+hp5U8REqccdSDn4BuMiJo4g9wpLSApTX013xy0F/+yYQmpUZMzPFt24QX4F 5pZ765brMrC8mjXLH0XdasjOeFRz/yxD0v5g8Xr9XuRTU1E05nBH0Qxq7reEruszy6mn NRQMSLjJlO3EdUXBLYsR+tYQhC3IR8aEAOUB3jCH1OcgLZ79RJHVAfp4o1jskUQ/IUER ZFIQ== X-Gm-Message-State: AOAM5328nOI2BunR3to7jVwuvdFhH131khfHW5kQAI7CGwHE/J5j/wcf EL6So1rTpFdtwrzUrt6fmAs= X-Google-Smtp-Source: ABdhPJy+rXHZam/ZjYMreNWMXR6YOu2irqO/I5ZNSMTlDazoeNOzOkGDuQpFmNX1ECrzpiTT2N4iMg== X-Received: by 2002:a62:dd03:: with SMTP id w3mr18852903pff.76.1590449383322; Mon, 25 May 2020 16:29:43 -0700 (PDT) Received: from dtor-ws ([2620:15c:202:201:3c2a:73a9:c2cf:7f45]) by smtp.gmail.com with ESMTPSA id h4sm14649006pje.29.2020.05.25.16.29.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 25 May 2020 16:29:42 -0700 (PDT) Date: Mon, 25 May 2020 16:29:40 -0700 From: Dmitry Torokhov To: Greg Kroah-Hartman Cc: Jiri Slaby , linux-kernel@vger.kernel.org, Kyungtae Kim Subject: Re: [PATCH v3] vt: keyboard: avoid signed integer overflow in k_ascii Message-ID: <20200525232940.GG89269@dtor-ws> References: <20200525232740.GA262061@dtor-ws> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200525232740.GA262061@dtor-ws> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [ Sorry, forgot to CC Kyungtae ] On Mon, May 25, 2020 at 04:27:40PM -0700, Dmitry Torokhov wrote: > When k_ascii is invoked several times in a row there is a potential for > signed integer overflow: > > UBSAN: Undefined behaviour in drivers/tty/vt/keyboard.c:888:19 signed integer overflow: > 10 * 1111111111 cannot be represented in type 'int' > CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.6.11 #1 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 > Call Trace: > > __dump_stack lib/dump_stack.c:77 [inline] > dump_stack+0xce/0x128 lib/dump_stack.c:118 > ubsan_epilogue+0xe/0x30 lib/ubsan.c:154 > handle_overflow+0xdc/0xf0 lib/ubsan.c:184 > __ubsan_handle_mul_overflow+0x2a/0x40 lib/ubsan.c:205 > k_ascii+0xbf/0xd0 drivers/tty/vt/keyboard.c:888 > kbd_keycode drivers/tty/vt/keyboard.c:1477 [inline] > kbd_event+0x888/0x3be0 drivers/tty/vt/keyboard.c:1495 > > While it can be worked around by using check_mul_overflow()/ > check_add_overflow(), it is better to introduce a separate flag to > signal that number pad is being used to compose a symbol, and > change type of the accumulator from signed to unsigned, thus > avoiding undefined behavior when it overflows. > > Reported-by: Kyungtae Kim > Signed-off-by: Dmitry Torokhov > --- > > - marking the patch as v3 as it is a successor of Kyungtae's patches. > > drivers/tty/vt/keyboard.c | 26 ++++++++++++++++---------- > 1 file changed, 16 insertions(+), 10 deletions(-) > > diff --git a/drivers/tty/vt/keyboard.c b/drivers/tty/vt/keyboard.c > index 15d33fa0c925..568b2171f335 100644 > --- a/drivers/tty/vt/keyboard.c > +++ b/drivers/tty/vt/keyboard.c > @@ -127,7 +127,11 @@ static DEFINE_SPINLOCK(func_buf_lock); /* guard 'func_buf' and friends */ > static unsigned long key_down[BITS_TO_LONGS(KEY_CNT)]; /* keyboard key bitmap */ > static unsigned char shift_down[NR_SHIFT]; /* shift state counters.. */ > static bool dead_key_next; > -static int npadch = -1; /* -1 or number assembled on pad */ > + > +/* Handles a number being assembled on the number pad */ > +static bool npadch_active; > +static unsigned int npadch_value; > + > static unsigned int diacr; > static char rep; /* flag telling character repeat */ > > @@ -845,12 +849,12 @@ static void k_shift(struct vc_data *vc, unsigned char value, char up_flag) > shift_state &= ~(1 << value); > > /* kludge */ > - if (up_flag && shift_state != old_state && npadch != -1) { > + if (up_flag && shift_state != old_state && npadch_active) { > if (kbd->kbdmode == VC_UNICODE) > - to_utf8(vc, npadch); > + to_utf8(vc, npadch_value); > else > - put_queue(vc, npadch & 0xff); > - npadch = -1; > + put_queue(vc, npadch_value & 0xff); > + npadch_active = false; > } > } > > @@ -868,7 +872,7 @@ static void k_meta(struct vc_data *vc, unsigned char value, char up_flag) > > static void k_ascii(struct vc_data *vc, unsigned char value, char up_flag) > { > - int base; > + unsigned int base; > > if (up_flag) > return; > @@ -882,10 +886,12 @@ static void k_ascii(struct vc_data *vc, unsigned char value, char up_flag) > base = 16; > } > > - if (npadch == -1) > - npadch = value; > - else > - npadch = npadch * base + value; > + if (!npadch_active) { > + npadch_value = 0; > + npadch_active = true; > + } > + > + npadch_value = npadch_value * base + value; > } > > static void k_lock(struct vc_data *vc, unsigned char value, char up_flag) > -- > 2.27.0.rc0.183.gde8f92d652-goog > > > -- > Dmitry -- Dmitry