From patchwork Tue Apr 5 07:17:48 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 558129 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6CDBAC433F5 for ; Tue, 5 Apr 2022 08:06:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233514AbiDEIHy (ORCPT ); Tue, 5 Apr 2022 04:07:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48140 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234899AbiDEH7D (ORCPT ); Tue, 5 Apr 2022 03:59:03 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 51770E094; Tue, 5 Apr 2022 00:53:23 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 6D6CBB81BAF; Tue, 5 Apr 2022 07:53:22 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CF488C340EE; Tue, 5 Apr 2022 07:53:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1649145201; bh=zEeKefMZYRslSx40JLS5O+6+t08QoeqPa7ZuL/Iyqg4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=U/C3R/o9zsgn5VKBMfkfq65/ar2+WqOhIPAJx59dHD8H2zYbU8CxEqS9ADGMh7mtX efQaaXDQIYrDRLMnSjtKyh8O+qX7LcDtm3wgsoZac0pQqBadzyhWqONc+szHsUHcA0 eZdeE8u3yQdSpfozk7MQR/G5ylP8F6XJlvagY+ow= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dan Carpenter , Helge Deller , Sasha Levin Subject: [PATCH 5.17 0321/1126] video: fbdev: fbcvt.c: fix printing in fb_cvt_print_name() Date: Tue, 5 Apr 2022 09:17:48 +0200 Message-Id: <20220405070417.037970983@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220405070407.513532867@linuxfoundation.org> References: <20220405070407.513532867@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Dan Carpenter [ Upstream commit 78482af095abd9f4f29f1aa3fe575d25c6ae3028 ] This code has two bugs: 1) "cnt" is 255 but the size of the buffer is 256 so the last byte is not used. 2) If we try to print more than 255 characters then "cnt" will be negative and that will trigger a WARN() in snprintf(). The fix for this is to use scnprintf() instead of snprintf(). We can re-write this code to be cleaner: 1) Rename "offset" to "off" because that's shorter. 2) Get rid of the "cnt" variable and just use "size - off" directly. 3) Get rid of the "read" variable and just increment "off" directly. Fixes: 96fe6a2109db ("fbdev: Add VESA Coordinated Video Timings (CVT) support") Signed-off-by: Dan Carpenter Signed-off-by: Helge Deller Signed-off-by: Sasha Levin --- drivers/video/fbdev/core/fbcvt.c | 53 +++++++++++++------------------- 1 file changed, 21 insertions(+), 32 deletions(-) diff --git a/drivers/video/fbdev/core/fbcvt.c b/drivers/video/fbdev/core/fbcvt.c index 55d2bd0ce5c0..64843464c661 100644 --- a/drivers/video/fbdev/core/fbcvt.c +++ b/drivers/video/fbdev/core/fbcvt.c @@ -214,9 +214,11 @@ static u32 fb_cvt_aspect_ratio(struct fb_cvt_data *cvt) static void fb_cvt_print_name(struct fb_cvt_data *cvt) { u32 pixcount, pixcount_mod; - int cnt = 255, offset = 0, read = 0; - u8 *buf = kzalloc(256, GFP_KERNEL); + int size = 256; + int off = 0; + u8 *buf; + buf = kzalloc(size, GFP_KERNEL); if (!buf) return; @@ -224,43 +226,30 @@ static void fb_cvt_print_name(struct fb_cvt_data *cvt) pixcount_mod = (cvt->xres * (cvt->yres/cvt->interlace)) % 1000000; pixcount_mod /= 1000; - read = snprintf(buf+offset, cnt, "fbcvt: %dx%d@%d: CVT Name - ", - cvt->xres, cvt->yres, cvt->refresh); - offset += read; - cnt -= read; + off += scnprintf(buf + off, size - off, "fbcvt: %dx%d@%d: CVT Name - ", + cvt->xres, cvt->yres, cvt->refresh); - if (cvt->status) - snprintf(buf+offset, cnt, "Not a CVT standard - %d.%03d Mega " - "Pixel Image\n", pixcount, pixcount_mod); - else { - if (pixcount) { - read = snprintf(buf+offset, cnt, "%d", pixcount); - cnt -= read; - offset += read; - } + if (cvt->status) { + off += scnprintf(buf + off, size - off, + "Not a CVT standard - %d.%03d Mega Pixel Image\n", + pixcount, pixcount_mod); + } else { + if (pixcount) + off += scnprintf(buf + off, size - off, "%d", pixcount); - read = snprintf(buf+offset, cnt, ".%03dM", pixcount_mod); - cnt -= read; - offset += read; + off += scnprintf(buf + off, size - off, ".%03dM", pixcount_mod); if (cvt->aspect_ratio == 0) - read = snprintf(buf+offset, cnt, "3"); + off += scnprintf(buf + off, size - off, "3"); else if (cvt->aspect_ratio == 3) - read = snprintf(buf+offset, cnt, "4"); + off += scnprintf(buf + off, size - off, "4"); else if (cvt->aspect_ratio == 1 || cvt->aspect_ratio == 4) - read = snprintf(buf+offset, cnt, "9"); + off += scnprintf(buf + off, size - off, "9"); else if (cvt->aspect_ratio == 2) - read = snprintf(buf+offset, cnt, "A"); - else - read = 0; - cnt -= read; - offset += read; - - if (cvt->flags & FB_CVT_FLAG_REDUCED_BLANK) { - read = snprintf(buf+offset, cnt, "-R"); - cnt -= read; - offset += read; - } + off += scnprintf(buf + off, size - off, "A"); + + if (cvt->flags & FB_CVT_FLAG_REDUCED_BLANK) + off += scnprintf(buf + off, size - off, "-R"); } printk(KERN_INFO "%s\n", buf);