Hi Dan,
> ----- Forwarded message from Dan Carpenter<[email protected]> -----
>
> Date: Mon, 20 Feb 2012 12:50:19 +0300
> From: Dan Carpenter<[email protected]>
> To: Tom Tucker<[email protected]>
> Cc: "J. Bruce Fields"<[email protected]>, [email protected], [email protected]
> Subject: question about map_read_chunks()
>
> 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?
Yes, it is. All these values should be clamped by the wsize/rsize,
however, I don't think we enforce that. We should add a check to
svc_rdma_xdr_decode_req().
>
> 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.
Without the proposed check, it can.
> 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?
I think it could cause bad things to happen, yes.
>
> 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.
I suppose, in theory, we could have a r/wsize > 2G, in which case, you are
correct.
> 165 rpl_map->sge[sge_no].iov_len = sge_bytes;
>
> regards,
> dan carpenter
>
I think adding a check to svc_rdma_xdr_decode_req() would avoid any
possibility of overflow. I'll code up a patch.
Thanks,
Tom
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.
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.
>> 165 rpl_map->sge[sge_no].iov_len = sge_bytes;
>>
>> regards,
>> dan carpenter
> --
> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html