From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from userp1040.oracle.com ([156.151.31.81]:18262 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751101AbdHVQl5 (ORCPT ); Tue, 22 Aug 2017 12:41:57 -0400 Date: Tue, 22 Aug 2017 09:41:34 -0700 From: "Darrick J. Wong" Subject: Re: another possible integer truncation in xfs Message-ID: <20170822164134.GV4796@magnolia> References: <12EF8D94C6F8734FB2FF37B9FBEDD173010E035CD2@EXCHANGE.collogia.de> <20170821081603.GA6581@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170821081603.GA6581@lst.de> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Christoph Hellwig Cc: Markus Stockhausen , "pmenzel@molgen.mpg.de" , "linux-xfs@vger.kernel.org" On Mon, Aug 21, 2017 at 10:16:03AM +0200, Christoph Hellwig wrote: > On Mon, Aug 21, 2017 at 08:01:03AM +0000, Markus Stockhausen wrote: > > Hi Christoph, > > > > out of curiosity I looked for other use cases of min_t in xfs. At least > > until 4.12 there is a similar constellation in xfs_dir2_leaf_readbuf: > > > > if (trim_map) { > > mip->map_blocks -= geo->fsbcount; > > /* > > * Loop to get rid of the extents for the > > * directory block. > > */ > > for (i = geo->fsbcount; i > 0; ) { > > j = min_t(int, map->br_blockcount, i); > > map->br_blockcount -= j; > > map->br_startblock += j; > > map->br_startoff += j; > > > > The loop could go havoc if map->br_blockcount is larger than > > 2G. If you think it could classify for stable feel free to add it too. "2G"... are you concerned about an integer overflow if map->br_blockcount is a value larger than 2147483647, or if *map itself represents an extent longer than 2GiB? (I'm pretty sure you're talking about the first scenario, but the units here are ambiguous.) I /think/ the correct answer here is that file extent records can't ever be longer than 2^20 blocks so this min_t ought to be fine. --D > I don't think it has a chance to be larger in practice, but we should > fix it anyway. I'll prepare a patch. > > Thanks for spotting this! > -- > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html