From patchwork Tue Dec 2 19:47:38 2008 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: roel kluin X-Patchwork-Id: 11822 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.176.167]) by ozlabs.org (Postfix) with ESMTP id 67F9DDDDDF for ; Wed, 3 Dec 2008 06:47:42 +1100 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754478AbYLBTrk (ORCPT ); Tue, 2 Dec 2008 14:47:40 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754573AbYLBTrk (ORCPT ); Tue, 2 Dec 2008 14:47:40 -0500 Received: from ug-out-1314.google.com ([66.249.92.168]:16715 "EHLO ug-out-1314.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754478AbYLBTrj (ORCPT ); Tue, 2 Dec 2008 14:47:39 -0500 Received: by ug-out-1314.google.com with SMTP id 39so3163100ugf.37 for ; Tue, 02 Dec 2008 11:47:37 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from :user-agent:mime-version:to:cc:subject:references:in-reply-to :content-type:content-transfer-encoding; bh=CQ53RKe4cESMLQOxNRI5/1H6BfHn+oh6yweeWlV70dI=; b=Pf70j4/N0wvBhcSQyWceO0ZRK4yY9oy5rfG+tWZhiM50P30/2prdhKDzAKL8widf4V 1wSgVbMrn67Q08S3DQqV+zDqri/wOQVVRdiLALMbi1N3iWeW/PEgrncQ8RoQexv6GFtN uePwWkGTyEizI2x8/A2MAJ+Le6zAXjim9hCfA= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:user-agent:mime-version:to:cc:subject :references:in-reply-to:content-type:content-transfer-encoding; b=Se9dQTKeGruktbAxVc16QES4zIWKoaJTcNuHZtDxlfcBLuixMtJhWV9lQV67xD/Uu+ 7dy4b9FjadgZOFbPxJk+1TmjJDEAC79o3ZPU+/2A/5x9Tq/gGmxHbvWDlO5hilNy3oG0 Jjsa1Yh2VAi3mQ7vTGvHkxCZP8RzAQ7RpizP8= Received: by 10.66.222.6 with SMTP id u6mr1001449ugg.19.1228247257489; Tue, 02 Dec 2008 11:47:37 -0800 (PST) Received: from ?192.168.1.148? (d133062.upc-d.chello.nl [213.46.133.62]) by mx.google.com with ESMTPS id o24sm12183327ugd.31.2008.12.02.11.47.35 (version=TLSv1/SSLv3 cipher=RC4-MD5); Tue, 02 Dec 2008 11:47:35 -0800 (PST) Message-ID: <493590DA.1090504@gmail.com> Date: Tue, 02 Dec 2008 20:47:38 +0100 From: Roel Kluin User-Agent: Thunderbird 2.0.0.14 (X11/20080421) MIME-Version: 1.0 To: Bill Davidsen CC: Theodore Tso , adilger@sun.com, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] ext3, ext4: do_split() fix loop, with obvious unsigned wrap References: <49343AD9.4020606@gmail.com> <20081202132441.GC16172@mit.edu> <49356B96.7070900@tmr.com> In-Reply-To: <49356B96.7070900@tmr.com> Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org Bill Davidsen wrote: > the value inside the loop is > correct (or at least is the same as the original patch). I agree, this can be shown with: #include int main() { unsigned int i, count = 10; printf ("The original loop:\n"); for (i = count-1; i >= 0; i--) { printf ("%u, ", i); if (i == -1) { printf ("which is wrong.\n"); break; } } printf ("As suggested by Bill:\n"); for (i = count; i--; ) printf ("%u, ", i); printf ("...After the loop i=%u\n"); printf ("Your suggestion:\n"); i = count; while (i--) printf ("%u, ", i); printf ("...After the loop i=%u\n"); return 0; } > Theodore Tso wrote: >> probably >> the best way of handling this is to recast it not as a for loop, but >> as a while loop. Ok, with me. As also shown this will give the same results: -----------8<--------------->8------------- Fix loop, with obvious unsigned wrap Signed-off-by: Roel Kluin --- -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/fs/ext3/namei.c b/fs/ext3/namei.c index 3e5edc9..0e574d4 100644 --- a/fs/ext3/namei.c +++ b/fs/ext3/namei.c @@ -1188,7 +1188,8 @@ static struct ext3_dir_entry_2 *do_split(handle_t *handle, struct inode *dir, /* Split the existing block in the middle, size-wise */ size = 0; move = 0; - for (i = count-1; i >= 0; i--) { + i = count; + while (i--) { /* is more than half of this entry in 2nd half of the block? */ if (size + map[i].size/2 > blocksize/2) break; diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c index 63adcb7..b8903d4 100644 --- a/fs/ext4/namei.c +++ b/fs/ext4/namei.c @@ -1198,7 +1198,8 @@ static struct ext4_dir_entry_2 *do_split(handle_t *handle, struct inode *dir, /* Split the existing block in the middle, size-wise */ size = 0; move = 0; - for (i = count-1; i >= 0; i--) { + i = count; + while (i--) { /* is more than half of this entry in 2nd half of the block? */ if (size + map[i].size/2 > blocksize/2) break;