Return-Path: linux-nfs-owner@vger.kernel.org Received: from fieldses.org ([174.143.236.118]:47997 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752238Ab3I0UPX (ORCPT ); Fri, 27 Sep 2013 16:15:23 -0400 Date: Fri, 27 Sep 2013 16:15:19 -0400 To: Tom Tucker Cc: Dan Carpenter , Tom Tucker , "J. Bruce Fields" , netdev@vger.kernel.org, linux-nfs@vger.kernel.org Subject: Re: question about map_read_chunks() Message-ID: <20130927201519.GC22640@fieldses.org> References: <20120220095019.GA21338@elgon.mountain> <20130927122108.GF6247@mwanda> <5245A2DE.9020307@opengridcomputing.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <5245A2DE.9020307@opengridcomputing.com> From: "J. Bruce Fields" Sender: linux-nfs-owner@vger.kernel.org List-ID: On Fri, Sep 27, 2013 at 10:23:10AM -0500, Tom Tucker wrote: > Hi Dan, > > On 9/27/13 7:21 AM, Dan Carpenter wrote: > >I have looked at this again, and I still worry that it looks like a bug. > >(remote security related blah blah blah). > > > >regards, > >dan carpenter > > > >On Mon, Feb 20, 2012 at 12:50:19PM +0300, Dan Carpenter wrote: > >>I had a couple questions about some map_read_chunks(). > >> > >>net/sunrpc/xprtrdma/svc_rdma_recvfrom.c > >> > >> 150 ch_bytes = ntohl(ch->rc_target.rs_length); > >> ^^^^^^^^ > >>It look like this is 32 bits from the network? > >> > >> 151 head->arg.head[0] = rqstp->rq_arg.head[0]; > >> 152 head->arg.tail[0] = rqstp->rq_arg.tail[0]; > >> 153 head->arg.pages = &head->pages[head->count]; > >> 154 head->hdr_count = head->count; /* save count of hdr pages */ > >> 155 head->arg.page_base = 0; > >> 156 head->arg.page_len = ch_bytes; > >> 157 head->arg.len = rqstp->rq_arg.len + ch_bytes; > >> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > >>Can overflow. > >> 158 head->arg.buflen = rqstp->rq_arg.buflen + ch_bytes; > agreed. > >> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > >>Same. I didn't follow it through to see if an overflow matters. Does > >>it? > >> > >> 159 head->count++; > >> 160 chl_map->ch[0].start = 0; > >> 161 while (byte_count) { > >> 162 rpl_map->sge[sge_no].iov_base = > >> 163 page_address(rqstp->rq_arg.pages[page_no]) + page_off; > >> 164 sge_bytes = min_t(int, PAGE_SIZE-page_off, ch_bytes); > >> ^^^ > >>This is the wrong cast to use. A large ch_bytes would be counted as a > >>negative value and get around the cap here. > True, but if we validate the wire data like we should, that's > probably not an issue. Well, my last attempt to do rdma nfs io resulted in an instant server reboot, so I can take a look at this but it may be the least of our problems.... --b.