Re: [PATCH net] sctp: account stream padding length for reconf chunk

[Xin Long <lucien.xin@gmail.com>]

On Thu, Oct 14, 2021 at 4:27 AM Marcelo Ricardo Leitner
<marcelo.leitner@gmail.com> wrote:
>
> From: Eiichi Tsukata <eiichi.tsukata@nutanix.com>
>
> sctp_make_strreset_req() makes repeated calls to sctp_addto_chunk()
> which will automatically account for padding on each call. inreq and
> outreq are already 4 bytes aligned, but the payload is not and doing
> SCTP_PAD4(a + b) (which _sctp_make_chunk() did implicitly here) is
> different from SCTP_PAD4(a) + SCTP_PAD4(b) and not enough. It led to
> possible attempt to use more buffer than it was allocated and triggered
> a BUG_ON.
>
> Cc: Vlad Yasevich <vyasevich@gmail.com>
> Cc: Neil Horman <nhorman@tuxdriver.com>
> Cc: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Jakub Kicinski <kuba@kernel.org>
> Cc: linux-sctp@vger.kernel.org
> Cc: netdev@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Cc: Greg KH <gregkh@linuxfoundation.org>
> Fixes: cc16f00f6529 ("sctp: add support for generating stream reconf ssn reset request chunk")
> Reported-by: Eiichi Tsukata <eiichi.tsukata@nutanix.com>
> Signed-off-by: Eiichi Tsukata <eiichi.tsukata@nutanix.com>
> Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
> Signed-off-by: Marcelo Ricardo Leitner <mleitner@redhat.com>
> ---
>  net/sctp/sm_make_chunk.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
> index b8fa8f1a7277..c7503fd64915 100644
> --- a/net/sctp/sm_make_chunk.c
> +++ b/net/sctp/sm_make_chunk.c
> @@ -3697,7 +3697,7 @@ struct sctp_chunk *sctp_make_strreset_req(
>         outlen = (sizeof(outreq) + stream_len) * out;
>         inlen = (sizeof(inreq) + stream_len) * in;
>
> -       retval = sctp_make_reconf(asoc, outlen + inlen);
> +       retval = sctp_make_reconf(asoc, SCTP_PAD4(outlen) + SCTP_PAD4(inlen));
>         if (!retval)
>                 return NULL;
>
> --
> 2.31.1
>
Reviewed-by: Xin Long <lucien.xin@gmail.com>