netdev - Re: question about map_read

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Message-ID: <20130927122108.GF6247@mwanda>
Date:	Fri, 27 Sep 2013 15:21:08 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	Tom Tucker <tom@....us>
Cc:	"J. Bruce Fields" <bfields@...hat.com>, netdev@...r.kernel.org,
	linux-nfs@...r.kernel.org
Subject: Re: question about map_read_chunks()

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
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