Re: [PATCH] sctp: Fix kernel panic while process protocol violation

[Wei Yongjun <yjwei@cn.fujitsu.com>]

Vlad Yasevich wrote:
> Wei Yongjun wrote:
>   
>> Since call to function sctp_sf_abort_violation() need paramter 'arg' with
>> 'struct sctp_chunk' type, it will read the chunk type and chunk length from
>> the chunk_hdr member of chunk. But call to sctp_sf_violation_paramlen()
>> always with 'struct sctp_paramhdr' type's parameter, it will be passed to
>> sctp_sf_abort_violation(). This may cause kernel panic.
>>
>>    sctp_sf_violation_paramlen()
>>      |-- sctp_sf_abort_violation()
>>         |-- sctp_make_abort_violation()
>>
>> This patch fixed this problem by add a new paramter 'struct sctp_paramhdr'
>> to sctp_make_abort_violation(), if param is not NULL, encode phdr with
>> param,
>> if param is NULL, encode phdr with chunk.
>>
>> This patch also fix two place which called sctp_sf_violation_paramlen()
>> with
>> wrong paramter type.
>>     
>
> GAK!!!  Thanks for finding this.
>
> I am not sure I am very happy this approach though...
>
> sctp_sf_violation_paramlen() is only used in processing of ascof/asconf_ack,
> so changing generic ABORT generation to track another argument is not the
> cleanest solution...
>
> In addition, we also have sctp_process_inv_paramlength() which is almost
> the same thing as sctp_sf_violation_paramlen().  So, I think it would
> be a good idea to have this code cleaned up and merged into a single
> function that can be called from both palaces.
>
> Part of the problem is that INIT processing expects an error chunk instead
> of the abort.  However, it's being rather dense in that regard and should
> be taught how to handle both.
>   

Here error chunk is not need, because this is a fatal error and will 
send ABORT which only use
the payload of this chunk. So, used abort has the same effect.
> Once that happens, sctp_process_inv_paramlength() can start returning
> an ABORT chunk back just like sctp_sf_violation_paramlen().  An once
> that happens, we can call this one function from everywhere.
>   
[PATCHv2] sctp: Fix kernel panic while process protocol violation parameter

Since call to function sctp_sf_abort_violation() need paramter 'arg' with
'struct sctp_chunk' type, it will read the chunk type and chunk length from
the chunk_hdr member of chunk. But call to sctp_sf_violation_paramlen()
always with 'struct sctp_paramhdr' type's parameter, it will be passed to
sctp_sf_abort_violation(). This may cause kernel panic.

   sctp_sf_violation_paramlen()
     |-- sctp_sf_abort_violation()
        |-- sctp_make_abort_violation()

This patch fixed this problem. This patch also fix two place which called
sctp_sf_violation_paramlen() with wrong paramter type.

Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
---
 include/net/sctp/sm.h    |    3 ++
 net/sctp/sm_make_chunk.c |   37 +++++++++++++++++++++++------------
 net/sctp/sm_statefuns.c  |   48 +++++++++++++++++++++++++++++++++++----------
 3 files changed, 64 insertions(+), 24 deletions(-)

diff --git a/include/net/sctp/sm.h b/include/net/sctp/sm.h
index 2481173..029a54a 100644
--- a/include/net/sctp/sm.h
+++ b/include/net/sctp/sm.h
@@ -227,6 +227,9 @@ struct sctp_chunk *sctp_make_abort_violation(const struct sctp_association *,
 				   const struct sctp_chunk *,
 				   const __u8 *,
 				   const size_t );
+struct sctp_chunk *sctp_make_violation_paramlen(const struct sctp_association *,
+				   const struct sctp_chunk *,
+				   struct sctp_paramhdr *);
 struct sctp_chunk *sctp_make_heartbeat(const struct sctp_association *,
 				  const struct sctp_transport *,
 				  const void *payload,
diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index e8ca4e5..dbc4394 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -1012,6 +1012,29 @@ end:
 	return retval;
 }
 
+struct sctp_chunk *sctp_make_violation_paramlen(
+	const struct sctp_association *asoc,
+	const struct sctp_chunk *chunk,
+	struct sctp_paramhdr *param)
+{
+	struct sctp_chunk *retval;
+	static const char error[] = "The following parameter had invalid length:";
+	size_t payload_len = WORD_ROUND(sizeof(error)) + sizeof(sctp_errhdr_t) +
+						sizeof(sctp_paramhdr_t);
+
+	retval = sctp_make_abort(asoc, chunk, payload_len);
+	if (!retval)
+		goto nodata;
+
+	sctp_init_cause(retval, SCTP_ERROR_PROTO_VIOLATION,
+			sizeof(error) + sizeof(sctp_paramhdr_t));
+	sctp_addto_chunk(retval, sizeof(error), error);
+	sctp_addto_param(retval, sizeof(sctp_paramhdr_t), param);
+
+nodata:
+	return retval;
+}
+
 /* Make a HEARTBEAT chunk.  */
 struct sctp_chunk *sctp_make_heartbeat(const struct sctp_association *asoc,
 				  const struct sctp_transport *transport,
@@ -1782,11 +1805,6 @@ static int sctp_process_inv_paramlength(const struct sctp_association *asoc,
 					const struct sctp_chunk *chunk,
 					struct sctp_chunk **errp)
 {
-	static const char error[] = "The following parameter had invalid length:";
-	size_t		payload_len = WORD_ROUND(sizeof(error)) +
-						sizeof(sctp_paramhdr_t);
-
-
 	/* This is a fatal error.  Any accumulated non-fatal errors are
 	 * not reported.
 	 */
@@ -1794,14 +1812,7 @@ static int sctp_process_inv_paramlength(const struct sctp_association *asoc,
 		sctp_chunk_free(*errp);
 
 	/* Create an error chunk and fill it in with our payload. */
-	*errp = sctp_make_op_error_space(asoc, chunk, payload_len);
-
-	if (*errp) {
-		sctp_init_cause(*errp, SCTP_ERROR_PROTO_VIOLATION,
-				sizeof(error) + sizeof(sctp_paramhdr_t));
-		sctp_addto_chunk(*errp, sizeof(error), error);
-		sctp_addto_param(*errp, sizeof(sctp_paramhdr_t), param);
-	}
+	*errp = sctp_make_violation_paramlen(asoc, chunk, param);
 
 	return 0;
 }
diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
index 8848d32..7c622af 100644
--- a/net/sctp/sm_statefuns.c
+++ b/net/sctp/sm_statefuns.c
@@ -119,7 +119,7 @@ static sctp_disposition_t sctp_sf_violation_paramlen(
 				     const struct sctp_endpoint *ep,
 				     const struct sctp_association *asoc,
 				     const sctp_subtype_t type,
-				     void *arg,
+				     void *arg, void *ext,
 				     sctp_cmd_seq_t *commands);
 
 static sctp_disposition_t sctp_sf_violation_ctsn(
@@ -3425,7 +3425,7 @@ sctp_disposition_t sctp_sf_do_asconf(const struct sctp_endpoint *ep,
 	addr_param = (union sctp_addr_param *)hdr->params;
 	length = ntohs(addr_param->p.length);
 	if (length < sizeof(sctp_paramhdr_t))
-		return sctp_sf_violation_paramlen(ep, asoc, type,
+		return sctp_sf_violation_paramlen(ep, asoc, type, arg,
 			   (void *)addr_param, commands);
 
 	/* Verify the ASCONF chunk before processing it. */
@@ -3433,8 +3433,8 @@ sctp_disposition_t sctp_sf_do_asconf(const struct sctp_endpoint *ep,
 			    (sctp_paramhdr_t *)((void *)addr_param + length),
 			    (void *)chunk->chunk_end,
 			    &err_param))
-		return sctp_sf_violation_paramlen(ep, asoc, type,
-						  (void *)&err_param, commands);
+		return sctp_sf_violation_paramlen(ep, asoc, type, arg,
+						  (void *)err_param, commands);
 
 	/* ADDIP 5.2 E1) Compare the value of the serial number to the value
 	 * the endpoint stored in a new association variable
@@ -3542,8 +3542,8 @@ sctp_disposition_t sctp_sf_do_asconf_ack(const struct sctp_endpoint *ep,
 	    (sctp_paramhdr_t *)addip_hdr->params,
 	    (void *)asconf_ack->chunk_end,
 	    &err_param))
-		return sctp_sf_violation_paramlen(ep, asoc, type,
-			   (void *)&err_param, commands);
+		return sctp_sf_violation_paramlen(ep, asoc, type, arg,
+			   (void *)err_param, commands);
 
 	if (last_asconf) {
 		addip_hdr = (sctp_addiphdr_t *)last_asconf->subh.addip_hdr;
@@ -4240,12 +4240,38 @@ static sctp_disposition_t sctp_sf_violation_paramlen(
 				     const struct sctp_endpoint *ep,
 				     const struct sctp_association *asoc,
 				     const sctp_subtype_t type,
-				     void *arg,
-				     sctp_cmd_seq_t *commands) {
-	static const char err_str[] = "The following parameter had invalid length:";
+				     void *arg, void *ext,
+				     sctp_cmd_seq_t *commands)
+{
+	struct sctp_chunk *chunk =  arg;
+	struct sctp_paramhdr *param = ext;
+	struct sctp_chunk *abort = NULL;
 
-	return sctp_sf_abort_violation(ep, asoc, arg, commands, err_str,
-					sizeof(err_str));
+	if (sctp_auth_recv_cid(SCTP_CID_ABORT, asoc))
+		goto discard;
+
+	/* Make the abort chunk. */
+	abort = sctp_make_violation_paramlen(asoc, chunk, param);
+	if (!abort)
+		goto nomem;
+
+	sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(abort));
+	SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);
+
+	sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR,
+			SCTP_ERROR(ECONNABORTED));
+	sctp_add_cmd_sf(commands, SCTP_CMD_ASSOC_FAILED,
+			SCTP_PERR(SCTP_ERROR_PROTO_VIOLATION));
+	SCTP_DEC_STATS(SCTP_MIB_CURRESTAB);
+
+discard:
+	sctp_sf_pdiscard(ep, asoc, SCTP_ST_CHUNK(0), arg, commands);
+
+	SCTP_INC_STATS(SCTP_MIB_ABORTEDS);
+
+	return SCTP_DISPOSITION_ABORT;
+nomem:
+	return SCTP_DISPOSITION_NOMEM;
 }
 
 /* Handle a protocol violation when the peer trying to advance the
-- 
1.5.3.8