On Tue, Jun 26, 2018 at 8:02 PM, 吉藤英明
<hideaki.yoshifuji@xxxxxxxxxxxxxxxx> wrote:
> 2018-06-26 13:33 GMT+09:00 Xin Long <lucien.xin@xxxxxxxxx>:
>> On Tue, Jun 26, 2018 at 12:31 AM, Marcelo Ricardo Leitner
>> <marcelo.leitner@xxxxxxxxx> wrote:
>>> Hi,
>>>
>>> On Tue, Jun 26, 2018 at 01:12:00AM +0900, 吉藤英明 wrote:
>>>> Hi,
>>>>
>>>> 2018-06-25 22:03 GMT+09:00 Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>:
>>>> > On Mon, Jun 25, 2018 at 07:28:47AM -0400, Neil Horman wrote:
>>>> >> On Mon, Jun 25, 2018 at 04:31:26PM +0900, David Miller wrote:
>>>> >> > From: Xin Long <lucien.xin@xxxxxxxxx>
>>>> >> > Date: Mon, 25 Jun 2018 10:14:35 +0800
>>>> >> >
>>>> >> > > struct sctp_paddrparams {
>>>> >> > > @@ -773,6 +775,8 @@ struct sctp_paddrparams {
>>>> >> > > __u32 spp_pathmtu;
>>>> >> > > __u32 spp_sackdelay;
>>>> >> > > __u32 spp_flags;
>>>> >> > > + __u32 spp_ipv6_flowlabel;
>>>> >> > > + __u8 spp_dscp;
>>>> >> > > } __attribute__((packed, aligned(4)));
>>>> >> >
>>>> >> > I don't think you can change the size of this structure like this.
>>>> >> >
>>>> >> > This check in sctp_setsockopt_peer_addr_params():
>>>> >> >
>>>> >> > if (optlen != sizeof(struct sctp_paddrparams))
>>>> >> > return -EINVAL;
>>>> >> >
>>>> >> > is going to trigger in old kernels when executing programs
>>>> >> > built against the new struct definition.
>>>> >
>>>> > That will happen, yes, but do we really care about being future-proof
>>>> > here? I mean: if we also update such check(s) to support dealing with
>>>> > smaller-than-supported structs, newer kernels will be able to run
>>>> > programs built against the old struct, and the new one; while building
>>>> > using newer headers and running on older kernel may fool the
>>>> > application in other ways too (like enabling support for something
>>>> > that is available on newer kernel and that is not present in the older
>>>> > one).
>>>>
>>>> We should not break existing apps.
>>>> We still accept apps of pre-2.4 era without sin6_scope_id
>>>> (e.g., net/ipv6/af_inet6.c:inet6_bind()).
>>>
>>> Yes. That's what I tried to say. That is supporting an old app built
>>> with old kernel headers and running on a newer kernel, and not the
>>> other way around (an app built with fresh headers and running on an
>>> old kernel).
>> To make it, I will update the check like:
>>
>> diff --git a/net/sctp/socket.c b/net/sctp/socket.c
>> index 1df5d07..c949d8c 100644
>> --- a/net/sctp/socket.c
>> +++ b/net/sctp/socket.c
>> @@ -2715,13 +2715,18 @@ static int
>> sctp_setsockopt_peer_addr_params(struct sock *sk,
>> struct sctp_sock *sp = sctp_sk(sk);
>> int error;
>> int hb_change, pmtud_change, sackdelay_change;
>> + int plen = sizeof(params);
>> + int old_plen = plen - sizeof(u32) * 2;
>
> if (optlen < offsetof(struct sctp_paddrparams, spp_ipv6_flowlabel))
> maybe?
Hi, yoshfuji,
offsetof() is better. thank you.
>
>>
>> - if (optlen != sizeof(struct sctp_paddrparams))
>> + if (optlen != plen && optlen != old_plen)
>> return -EINVAL;
>>
>> if (copy_from_user(¶ms, optval, optlen))
>> return -EFAULT;
>>
>> + if (optlen == old_plen)
>> + params.spp_flags &= ~(SPP_DSCP | SPP_IPV6_FLOWLABEL);
>
> I think we should return -EINVAL if size is not new one.
Sorry, if we returned -EINVAL when size is the old one,
how can we guarantee an old app built with old kernel
headers and running on a newer kernel works well?
or you meant?
if ((params.spp_flags & (SPP_DSCP | SPP_IPV6_FLOWLABEL)) &&
optlen != plen)
return EINVAL;
>
> --yoshfuji
>
>> +
>> /* Validate flags and value parameters. */
>> hb_change = params.spp_flags & SPP_HB;
>> pmtud_change = params.spp_flags & SPP_PMTUD;
>> @@ -5591,10 +5596,13 @@ static int
>> sctp_getsockopt_peer_addr_params(struct sock *sk, int len,
>> struct sctp_transport *trans = NULL;
>> struct sctp_association *asoc = NULL;
>> struct sctp_sock *sp = sctp_sk(sk);
>> + int plen = sizeof(params);
>> + int old_plen = plen - sizeof(u32) * 2;
>>
>> - if (len < sizeof(struct sctp_paddrparams))
>> + if (len < old_plen)
>> return -EINVAL;
>> - len = sizeof(struct sctp_paddrparams);
>> +
>> + len = len >= plen ? plen : old_plen;
>> if (copy_from_user(¶ms, optval, len))
>> return -EFAULT;
>>
>> does it look ok to you?
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