Re: [PATCH v2 mptcp-net] mptcp: fix 32 bit DSN expansion

[Mat Martineau <mathew.j.martineau@linux.intel.com>]

On Wed, 16 Jun 2021, Paolo Abeni wrote:

> The current implementation of 32 bit DSN expansion is buggy.
> After the previous patch, we can simply reuse the newly
> introduced helper to do the expansion safely.
>
> Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/120
> Fixes: 648ef4b88673 ("mptcp: Implement MPTCP receive path")
> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> ---
> v1 -> v2:
> - fix typo in the commit message
> - use the common helper

Thanks for the v2, looks good to me.

Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>


> ---
> net/mptcp/subflow.c | 17 +----------------
> 1 file changed, 1 insertion(+), 16 deletions(-)
>
> diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
> index d55f4ef736a5..6772802737e4 100644
> --- a/net/mptcp/subflow.c
> +++ b/net/mptcp/subflow.c
> @@ -781,15 +781,6 @@ enum mapping_status {
> 	MAPPING_DUMMY
> };
>
> -static u64 expand_seq(u64 old_seq, u16 old_data_len, u64 seq)
> -{
> -	if ((u32)seq == (u32)old_seq)
> -		return old_seq;
> -
> -	/* Assume map covers data not mapped yet. */
> -	return seq | ((old_seq + old_data_len + 1) & GENMASK_ULL(63, 32));
> -}
> -
> static void dbg_bad_map(struct mptcp_subflow_context *subflow, u32 ssn)
> {
> 	pr_debug("Bad mapping: ssn=%d map_seq=%d map_data_len=%d",
> @@ -995,13 +986,7 @@ static enum mapping_status get_mapping_status(struct sock *ssk,
> 		data_len--;
> 	}
>
> -	if (!mpext->dsn64) {
> -		map_seq = expand_seq(subflow->map_seq, subflow->map_data_len,
> -				     mpext->data_seq);
> -		pr_debug("expanded seq=%llu", subflow->map_seq);
> -	} else {
> -		map_seq = mpext->data_seq;
> -	}
> +	map_seq = mptcp_expand_seq(READ_ONCE(msk->ack_seq), mpext->data_seq, mpext->dsn64);
> 	WRITE_ONCE(mptcp_sk(subflow->conn)->use_64bit_ack, !!mpext->dsn64);
>
> 	if (subflow->map_valid) {
> -- 
> 2.26.3
>
>
>

--
Mat Martineau
Intel