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=-6.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, 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 5CEE4C10DCE for ; Sun, 15 Mar 2020 10:34:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1CD7B205C9 for ; Sun, 15 Mar 2020 10:34:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=onstation.org header.i=@onstation.org header.b="sDnevCUt" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728250AbgCOKd7 (ORCPT ); Sun, 15 Mar 2020 06:33:59 -0400 Received: from onstation.org ([52.200.56.107]:38084 "EHLO onstation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728247AbgCOKd7 (ORCPT ); Sun, 15 Mar 2020 06:33:59 -0400 Received: from localhost (c-98-239-145-235.hsd1.wv.comcast.net [98.239.145.235]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: masneyb) by onstation.org (Postfix) with ESMTPSA id 7CCAF3E9FD; Sun, 15 Mar 2020 10:33:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=onstation.org; s=default; t=1584268438; bh=ck55uNYScn7NP8oBNgNFD+lyQRvJgEekOPCBFjDlO+Q=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=sDnevCUtB9FKpYLrFUr3f1qELnKmkL1QML1WHIDAdpUeCiVcSTFAuiI2g/QDsDuDd 27uSxUfCbA96aGmZa3EM90NVohTwHMs+1JFiGlL7zXbC1ymKDVSHX92MRgr8hzI84l OwOTz4A7T2XgfeyiiuRd4DnA36g5HMwgiQFGrjWI= Date: Sun, 15 Mar 2020 06:33:58 -0400 From: Brian Masney To: Jonathan Cameron Cc: Takashi Iwai , linux-iio@vger.kernel.org Subject: Re: [PATCH 2/2] iio: tsl2772: Use scnprintf() for avoiding potential buffer overflow Message-ID: <20200315103358.GA4674@onstation.org> References: <20200311074325.7922-1-tiwai@suse.de> <20200311074325.7922-3-tiwai@suse.de> <20200315095834.76f50454@archlinux> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200315095834.76f50454@archlinux> Sender: linux-iio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org On Sun, Mar 15, 2020 at 09:58:34AM +0000, Jonathan Cameron wrote: > On Wed, 11 Mar 2020 08:43:25 +0100 > Takashi Iwai wrote: > > > Since snprintf() returns the would-be-output size instead of the > > actual output size, the succeeding calls may go beyond the given > > buffer limit. Fix it by replacing with scnprintf(). > > > > Signed-off-by: Takashi Iwai > > This one is printing a short well defined list of values. No way they go > anywhere near the smallest possible PAGE_SIZE buffer that it's printing > into. > > Which is handy given the remaining space isn't adjusted as we add items > to the string. Hence even with scnprintf it would overflow. > > Brian, can you take a look at this when you get a moment? I also agree that this won't overflow in practice, however we should fix this up. Maybe the scnprintf() calls should be this: offset += scnprintf(buf + offset, PAGE_SIZE - offset, ...); Brian > > Thanks, > > Jonathan > > > --- > > drivers/iio/light/tsl2772.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/iio/light/tsl2772.c b/drivers/iio/light/tsl2772.c > > index be37fcbd4654..44a0b56a558c 100644 > > --- a/drivers/iio/light/tsl2772.c > > +++ b/drivers/iio/light/tsl2772.c > > @@ -986,7 +986,7 @@ static ssize_t in_illuminance0_lux_table_show(struct device *dev, > > int offset = 0; > > > > while (i < TSL2772_MAX_LUX_TABLE_SIZE) { > > - offset += snprintf(buf + offset, PAGE_SIZE, "%u,%u,", > > + offset += scnprintf(buf + offset, PAGE_SIZE, "%u,%u,", > > chip->tsl2772_device_lux[i].ch0, > > chip->tsl2772_device_lux[i].ch1); > > if (chip->tsl2772_device_lux[i].ch0 == 0) { > > @@ -1000,7 +1000,7 @@ static ssize_t in_illuminance0_lux_table_show(struct device *dev, > > i++; > > } > > > > - offset += snprintf(buf + offset, PAGE_SIZE, "\n"); > > + offset += scnprintf(buf + offset, PAGE_SIZE, "\n"); > > return offset; > > } > >