[PATCH net] sctp: fix possible out-of-bounds read in SCTP_PARAM_SUPPORTED_ADDRESS_TYPES

From: Qing Luo <[email protected]>

While processing SCTP_PARAM_SUPPORTED_ADDRESS_TYPES in
sctp_process_param(), the length field is subtracted from
sizeof(struct sctp_paramhdr) and stored in a __u16 variable. If the
length is less than sizeof(struct sctp_paramhdr) (4 bytes), the unsigned
subtraction underflows, resulting in a value near 0xFFFF. The subsequent
for() loop then iterates far beyond the parameter boundaries, causing an
out-of-bounds read.

sctp_verify_param() performs no length validation for this parameter
type, so a malformed parameter with insufficient length can reach
sctp_process_param() through the INIT/INIT-ACK/COOKIE-ECHO processing
path.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: [email protected]
Signed-off-by: Qing Luo <[email protected]>
---
 net/sctp/sm_make_chunk.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index 236e25abc7a4..ebf791969454 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -2169,12 +2169,19 @@ static enum sctp_ierror sctp_verify_param(struct net *net,
 	case SCTP_PARAM_IPV4_ADDRESS:
 	case SCTP_PARAM_IPV6_ADDRESS:
 	case SCTP_PARAM_COOKIE_PRESERVATIVE:
-	case SCTP_PARAM_SUPPORTED_ADDRESS_TYPES:
 	case SCTP_PARAM_STATE_COOKIE:
 	case SCTP_PARAM_HEARTBEAT_INFO:
 	case SCTP_PARAM_UNRECOGNIZED_PARAMETERS:
 	case SCTP_PARAM_ECN_CAPABLE:
 		break;
+
+	case SCTP_PARAM_SUPPORTED_ADDRESS_TYPES:
+		if (ntohs(param.p->length) < sizeof(struct sctp_paramhdr)) {
+			sctp_process_inv_paramlength(asoc, param.p,
+						     chunk, err_chunk);
+			retval = SCTP_IERROR_ABORT;
+		}
+		break;
 	case SCTP_PARAM_ADAPTATION_LAYER_IND:
 		if (ntohs(param.p->length) != sizeof(*param.aind)) {
 			sctp_process_inv_paramlength(asoc, param.p,
@@ -2600,6 +2607,9 @@ static int sctp_process_param(struct sctp_association *asoc,
 			asoc->peer.ipv4_address = 1;
 
 		/* Cycle through address types; avoid divide by 0. */
+		if (ntohs(param.p->length) < sizeof(struct sctp_paramhdr))
+			break;
+
 		sat = ntohs(param.p->length) - sizeof(struct sctp_paramhdr);
 		if (sat)
 			sat /= sizeof(__u16);
-- 
2.25.1