On Mon, Nov 13, 2017 at 01:39:27PM +0800, Xin Long wrote:
> Now when resetting stream, if both in and out flags are set, the info
> len can reach:
> sizeof(struct sctp_strreset_outreq) + SCTP_MAX_STREAM(65535) +
> sizeof(struct sctp_strreset_inreq) + SCTP_MAX_STREAM(65535)
> even without duplicated stream no, this value is far greater than the
> chunk's max size.
>
> _sctp_make_chunk doesn't do any check for this, which would cause the
> skb it allocs is huge, syzbot even reported a crash due to this.
>
> This patch is to check stream reset info len before making reconf
> chunk and return NULL if the len exceeds chunk's capacity.
>
> Fixes: cc16f00f6529 ("sctp: add support for generating stream reconf ssn reset request chunk")
> Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
> Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
> ---
> net/sctp/sm_make_chunk.c | 7 +++++--
> net/sctp/stream.c | 8 +++++---
> 2 files changed, 10 insertions(+), 5 deletions(-)
>
> diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
> index 514465b..a21328a 100644
> --- a/net/sctp/sm_make_chunk.c
> +++ b/net/sctp/sm_make_chunk.c
> @@ -3598,14 +3598,17 @@ struct sctp_chunk *sctp_make_strreset_req(
> __u16 stream_len = stream_num * 2;
> struct sctp_strreset_inreq inreq;
> struct sctp_chunk *retval;
> - __u16 outlen, inlen;
> + int outlen, inlen;
>
> outlen = (sizeof(outreq) + stream_len) * out;
> inlen = (sizeof(inreq) + stream_len) * in;
>
> + if (outlen + inlen > SCTP_MAX_CHUNK_LEN - sizeof(struct sctp_chunkhdr))
> + return ERR_PTR(-EINVAL);
> +
Why all the ERR_PTR manipulations here? Just returning NULL, like the fuction
has been doing is sufficient to set ENOMEM at both call sites
Neil
> retval = sctp_make_reconf(asoc, outlen + inlen);
> if (!retval)
> - return NULL;
> + return ERR_PTR(-ENOMEM);
>
> if (outlen) {
> outreq.param_hdr.type = SCTP_PARAM_RESET_OUT_REQUEST;
> diff --git a/net/sctp/stream.c b/net/sctp/stream.c
> index fa8371f..51a25bf 100644
> --- a/net/sctp/stream.c
> +++ b/net/sctp/stream.c
> @@ -162,8 +162,8 @@ int sctp_send_reset_streams(struct sctp_association *asoc,
>
> kfree(nstr_list);
>
> - if (!chunk) {
> - retval = -ENOMEM;
> + if (IS_ERR(chunk)) {
> + retval = PTR_ERR(chunk);
> goto out;
> }
>
> @@ -482,8 +482,10 @@ struct sctp_chunk *sctp_process_strreset_inreq(
> }
>
> chunk = sctp_make_strreset_req(asoc, nums, str_p, 1, 0);
> - if (!chunk)
> + if (IS_ERR(chunk)) {
> + chunk = NULL;
> goto out;
> + }
>
> if (nums)
> for (i = 0; i < nums; i++)
> --
> 2.1.0
>
>
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