From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dan Carpenter Subject: Re: question about map_read_chunks() Date: Fri, 27 Sep 2013 15:21:08 +0300 Message-ID: <20130927122108.GF6247@mwanda> References: <20120220095019.GA21338@elgon.mountain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "J. Bruce Fields" , netdev@vger.kernel.org, linux-nfs@vger.kernel.org To: Tom Tucker Return-path: Received: from aserp1040.oracle.com ([141.146.126.69]:28027 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753216Ab3I0MVV (ORCPT ); Fri, 27 Sep 2013 08:21:21 -0400 Content-Disposition: inline In-Reply-To: <20120220095019.GA21338@elgon.mountain> Sender: netdev-owner@vger.kernel.org List-ID: 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; > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > 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. > > 165 rpl_map->sge[sge_no].iov_len = sge_bytes; > > regards, > dan carpenter