Commit message: sctp: account stream padding length for reconf chunk

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: 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>
Reviewed-by: Xin Long <lucien.xin@gmail.com>
Link: https://lore.kernel.org/r/b97c1f8b0c7ff79ac4ed206fc2c49d3612e0850c.1634156849.git.mleitner@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
CVE: CVE-2022-0322
CWE: CWE-704
Vulnerability description: A flaw was found in the sctp_make_strreset_req function in net/sctp/sm_make_chunk.c in the SCTP network protocol in the Linux kernel with a local user privilege access. In this flaw, an attempt to use more buffer than is allocated triggers a BUG_ON issue, leading to a denial of service (DOS).

Project: linux
File: sm_make_chunk.c

struct sctp_chunk *sctp_make_strreset_req(
					const struct sctp_association *asoc,
					__u16 stream_num, __be16 *stream_list,
					bool out, bool in)
{
	__u16 stream_len = stream_num * sizeof(__u16);
	struct sctp_strreset_outreq outreq;
	struct sctp_strreset_inreq inreq;
	struct sctp_chunk *retval;
	__u16 outlen, inlen;

	outlen = (sizeof(outreq) + stream_len) * out;
	inlen = (sizeof(inreq) + stream_len) * in;

	retval = sctp_make_reconf(asoc, outlen + inlen);
	if (!retval)
		return NULL;

	if (outlen) {
		outreq.param_hdr.type = SCTP_PARAM_RESET_OUT_REQUEST;
		outreq.param_hdr.length = htons(outlen);
		outreq.request_seq = htonl(asoc->strreset_outseq);
		outreq.response_seq = htonl(asoc->strreset_inseq - 1);
		outreq.send_reset_at_tsn = htonl(asoc->next_tsn - 1);

		sctp_addto_chunk(retval, sizeof(outreq), &outreq);

		if (stream_len)
			sctp_addto_chunk(retval, stream_len, stream_list);
	}

	if (inlen) {
		inreq.param_hdr.type = SCTP_PARAM_RESET_IN_REQUEST;
		inreq.param_hdr.length = htons(inlen);
		inreq.request_seq = htonl(asoc->strreset_outseq + out);

		sctp_addto_chunk(retval, sizeof(inreq), &inreq);

		if (stream_len)
			sctp_addto_chunk(retval, stream_len, stream_list);
	}

	return retval;
}

Project: linux
File: sm_make_chunk.c

struct sctp_chunk *sctp_make_strreset_req(
					const struct sctp_association *asoc,
					__u16 stream_num, __be16 *stream_list,
					bool out, bool in)
{
	__u16 stream_len = stream_num * sizeof(__u16);
	struct sctp_strreset_outreq outreq;
	struct sctp_strreset_inreq inreq;
	struct sctp_chunk *retval;
	__u16 outlen, inlen;

	outlen = (sizeof(outreq) + stream_len) * out;
	inlen = (sizeof(inreq) + stream_len) * in;

	retval = sctp_make_reconf(asoc, SCTP_PAD4(outlen) + SCTP_PAD4(inlen));
	if (!retval)
		return NULL;

	if (outlen) {
		outreq.param_hdr.type = SCTP_PARAM_RESET_OUT_REQUEST;
		outreq.param_hdr.length = htons(outlen);
		outreq.request_seq = htonl(asoc->strreset_outseq);
		outreq.response_seq = htonl(asoc->strreset_inseq - 1);
		outreq.send_reset_at_tsn = htonl(asoc->next_tsn - 1);

		sctp_addto_chunk(retval, sizeof(outreq), &outreq);

		if (stream_len)
			sctp_addto_chunk(retval, stream_len, stream_list);
	}

	if (inlen) {
		inreq.param_hdr.type = SCTP_PARAM_RESET_IN_REQUEST;
		inreq.param_hdr.length = htons(inlen);
		inreq.request_seq = htonl(asoc->strreset_outseq + out);

		sctp_addto_chunk(retval, sizeof(inreq), &inreq);

		if (stream_len)
			sctp_addto_chunk(retval, stream_len, stream_list);
	}

	return retval;
}