From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-fsdevel-owner@vger.kernel.org>
Received: from youngberry.canonical.com ([91.189.89.112]:59280 "EHLO
        youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1727475AbeHaRqp (ORCPT
        <rfc822;linux-fsdevel@vger.kernel.org>);
        Fri, 31 Aug 2018 13:46:45 -0400
To: linux-fsdevel@vger.kernel.org, David Howells <dhowells@redhat.com>,
        Al Viro <viro@zeniv.linux.org.uk>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
From: Colin Ian King <colin.king@canonical.com>
Subject: fs: hfs: Possible issue with increment of extent
Message-ID: <a519d1f2-81db-26c2-30ba-9ce2bacfecbe@canonical.com>
Date: Fri, 31 Aug 2018 14:39:11 +0100
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Sender: linux-fsdevel-owner@vger.kernel.org
List-ID: <linux-fsdevel.vger.kernel.org>

Hi,

Static analysis has picked up a potential issue with an out of bounds
read in fs/hfs/extent.c; the following for-loop in  hfs_free_fork()
increments i and also extent while also reading extent[i].count.  This
looks incorrect to me, I think the increment of extent is not needed:

        for (i = 0; i < 3; extent++, i++)
                blocks += be16_to_cpu(extent[i].count);

        res = hfs_free_extents(sb, extent, blocks, blocks);

I'm not familiar enough with the code to conclude that removing the
increment of extent is necessary a correct fix just in case I'm missing
something subtle here.

This issue was picked up by static analysis with CoverityScan:

CID 711541 (#1 of 1): Out-of-bounds read:
Overrunning array of 3 4-byte elements at element index 4 (byte offset
16) by dereferencing pointer extent + i.

Colin