On Mon, Nov 13, 2017 at 11:15:40PM +0800, Xin Long wrote:
> On Mon, Nov 13, 2017 at 11:09 PM, Neil Horman <nhorman@xxxxxxxxxxxxx> wrote:
> > 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
> I don't like ERR_PTR handling here either,
> But it shouldn't be ENOMEM, should it ?
>
> It may confuse users, but I'm also ok to let it just return
> ENOMEM as you wish. wdyt ?
>
I'm ok with ENOMEM. If someone tries to reconf the streams with huge values,
ENOMEM makes sense to me
Neil
> >
> > 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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