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sctp: Catch bogus stream sequence numbers

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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 <vladislav.yasevich@hp.com>
This commit is contained in:
Vlad Yasevich 2009-09-04 18:21:03 -04:00
parent be2971438d
commit f1751c57f7
1 changed files with 26 additions and 2 deletions
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28
net/sctp/sm_statefuns.c
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@ -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.