On Fri, May 26, 2017 at 1:14 AM, Davide Caratti <dcaratti@xxxxxxxxxx> wrote:
> sometimes ICMP replies to INIT chunks are ignored by the client, even if
> the encapsulated SCTP headers match an open socket. This happens when the
> ICMP packet is carried by a paged skb: use skb_header_pointer() to read
> packet contents beyond the SCTP header, so that chunk header and initiate
> tag are validated correctly.
>
> v2:
> - don't use skb_header_pointer() to read the transport header, since
> icmp_socket_deliver() already puts these 8 bytes in the linear area.
> - change commit message to make specific reference to INIT chunks.
>
> Signed-off-by: Davide Caratti <dcaratti@xxxxxxxxxx>
Thanks.
Reviewed-by: Xin Long <lucien.xin@xxxxxxxxx>
> ---
> net/sctp/input.c | 16 +++++++++-------
> 1 file changed, 9 insertions(+), 7 deletions(-)
>
> diff --git a/net/sctp/input.c b/net/sctp/input.c
> index 0e06a27..ba9ad32 100644
> --- a/net/sctp/input.c
> +++ b/net/sctp/input.c
> @@ -473,15 +473,14 @@ struct sock *sctp_err_lookup(struct net *net, int family, struct sk_buff *skb,
> struct sctp_association **app,
> struct sctp_transport **tpp)
> {
> + struct sctp_init_chunk *chunkhdr, _chunkhdr;
> union sctp_addr saddr;
> union sctp_addr daddr;
> struct sctp_af *af;
> struct sock *sk = NULL;
> struct sctp_association *asoc;
> struct sctp_transport *transport = NULL;
> - struct sctp_init_chunk *chunkhdr;
> __u32 vtag = ntohl(sctphdr->vtag);
> - int len = skb->len - ((void *)sctphdr - (void *)skb->data);
>
> *app = NULL; *tpp = NULL;
>
> @@ -516,13 +515,16 @@ struct sock *sctp_err_lookup(struct net *net, int family, struct sk_buff *skb,
> * discard the packet.
> */
> if (vtag == 0) {
> - chunkhdr = (void *)sctphdr + sizeof(struct sctphdr);
> - if (len < sizeof(struct sctphdr) + sizeof(sctp_chunkhdr_t)
> - + sizeof(__be32) ||
> + /* chunk header + first 4 octects of init header */
> + chunkhdr = skb_header_pointer(skb, skb_transport_offset(skb) +
> + sizeof(struct sctphdr),
> + sizeof(struct sctp_chunkhdr) +
> + sizeof(__be32), &_chunkhdr);
> + if (!chunkhdr ||
> chunkhdr->chunk_hdr.type != SCTP_CID_INIT ||
> - ntohl(chunkhdr->init_hdr.init_tag) != asoc->c.my_vtag) {
> + ntohl(chunkhdr->init_hdr.init_tag) != asoc->c.my_vtag)
> goto out;
> - }
> +
> } else if (vtag != asoc->c.peer_vtag) {
> goto out;
> }
> --
> 2.9.4
>
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