From f1751c57f7bb816c9b6b4cb5d79c703aaa7199da Mon Sep 17 00:00:00 2001 From: Vlad Yasevich Date: Fri, 4 Sep 2009 18:21:03 -0400 Subject: [PATCH] sctp: Catch bogus stream sequence numbers Since our TSN map is capable of holding at most a 4K chunk gap, there is no way that during this gap, a stream sequence number (unsigned short) can wrap such that the new number is smaller then the next expected one. If such a case is encountered, this is a protocol violation. Signed-off-by: Vlad Yasevich --- net/sctp/sm_statefuns.c | 28 ++++++++++++++++++++++++++-- 1 file changed, 26 insertions(+), 2 deletions(-) diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c index a7f18a352364..c8fae1983dd1 100644 --- a/net/sctp/sm_statefuns.c +++ b/net/sctp/sm_statefuns.c @@ -2891,6 +2891,9 @@ sctp_disposition_t sctp_sf_eat_data_6_2(const struct sctp_endpoint *ep, goto discard_force; case SCTP_IERROR_NO_DATA: goto consume; + case SCTP_IERROR_PROTO_VIOLATION: + return sctp_sf_abort_violation(ep, asoc, chunk, commands, + (u8 *)chunk->subh.data_hdr, sizeof(sctp_datahdr_t)); default: BUG(); } @@ -3001,6 +3004,9 @@ sctp_disposition_t sctp_sf_eat_data_fast_4_4(const struct sctp_endpoint *ep, break; case SCTP_IERROR_NO_DATA: goto consume; + case SCTP_IERROR_PROTO_VIOLATION: + return sctp_sf_abort_violation(ep, asoc, chunk, commands, + (u8 *)chunk->subh.data_hdr, sizeof(sctp_datahdr_t)); default: BUG(); } @@ -5877,6 +5883,9 @@ static int sctp_eat_data(const struct sctp_association *asoc, __u32 tsn; struct sctp_tsnmap *map = (struct sctp_tsnmap *)&asoc->peer.tsn_map; struct sock *sk = asoc->base.sk; + u16 ssn; + u16 sid; + u8 ordered = 0; data_hdr = chunk->subh.data_hdr = (sctp_datahdr_t *)chunk->skb->data; skb_pull(chunk->skb, sizeof(sctp_datahdr_t)); @@ -6016,8 +6025,10 @@ static int sctp_eat_data(const struct sctp_association *asoc, */ if (chunk->chunk_hdr->flags & SCTP_DATA_UNORDERED) SCTP_INC_STATS(SCTP_MIB_INUNORDERCHUNKS); - else + else { SCTP_INC_STATS(SCTP_MIB_INORDERCHUNKS); + ordered = 1; + } /* RFC 2960 6.5 Stream Identifier and Stream Sequence Number * @@ -6027,7 +6038,8 @@ static int sctp_eat_data(const struct sctp_association *asoc, * with cause set to "Invalid Stream Identifier" (See Section 3.3.10) * and discard the DATA chunk. */ - if (ntohs(data_hdr->stream) >= asoc->c.sinit_max_instreams) { + sid = ntohs(data_hdr->stream); + if (sid >= asoc->c.sinit_max_instreams) { /* Mark tsn as received even though we drop it */ sctp_add_cmd_sf(commands, SCTP_CMD_REPORT_TSN, SCTP_U32(tsn)); @@ -6040,6 +6052,18 @@ static int sctp_eat_data(const struct sctp_association *asoc, return SCTP_IERROR_BAD_STREAM; } + /* Check to see if the SSN is possible for this TSN. + * The biggest gap we can record is 4K wide. Since SSNs wrap + * at an unsigned short, there is no way that an SSN can + * wrap and for a valid TSN. We can simply check if the current + * SSN is smaller then the next expected one. If it is, it wrapped + * and is invalid. + */ + ssn = ntohs(data_hdr->ssn); + if (ordered && SSN_lt(ssn, sctp_ssn_peek(&asoc->ssnmap->in, sid))) { + return SCTP_IERROR_PROTO_VIOLATION; + } + /* Send the data up to the user. Note: Schedule the * SCTP_CMD_CHUNK_ULP cmd before the SCTP_CMD_GEN_SACK, as the SACK * chunk needs the updated rwnd. -- GitLab