diff --git a/include/net/sctp/sm.h b/include/net/sctp/sm.h
index bafe2a0ab9085f24e17038516c55c00cfddd02f4..ca6c971dd74aede829d4512ddf71006520c78f47 100644
--- a/include/net/sctp/sm.h
+++ b/include/net/sctp/sm.h
@@ -307,85 +307,27 @@ static inline __u16 sctp_data_size(struct sctp_chunk *chunk)
 }
 
 /* Compare two TSNs */
+#define TSN_lt(a,b)	\
+	(typecheck(__u32, a) && \
+	 typecheck(__u32, b) && \
+	 ((__s32)((a) - (b)) < 0))
 
-/* RFC 1982 - Serial Number Arithmetic
- *
- * 2. Comparison
- *  Then, s1 is said to be equal to s2 if and only if i1 is equal to i2,
- *  in all other cases, s1 is not equal to s2.
- *
- * s1 is said to be less than s2 if, and only if, s1 is not equal to s2,
- * and
- *
- *      (i1 < i2 and i2 - i1 < 2^(SERIAL_BITS - 1)) or
- *      (i1 > i2 and i1 - i2 > 2^(SERIAL_BITS - 1))
- *
- * s1 is said to be greater than s2 if, and only if, s1 is not equal to
- * s2, and
- *
- *      (i1 < i2 and i2 - i1 > 2^(SERIAL_BITS - 1)) or
- *      (i1 > i2 and i1 - i2 < 2^(SERIAL_BITS - 1))
- */
-
-/*
- * RFC 2960
- *  1.6 Serial Number Arithmetic
- *
- * Comparisons and arithmetic on TSNs in this document SHOULD use Serial
- * Number Arithmetic as defined in [RFC1982] where SERIAL_BITS = 32.
- */
-
-enum {
-	TSN_SIGN_BIT = (1<<31)
-};
-
-static inline int TSN_lt(__u32 s, __u32 t)
-{
-	return ((s) - (t)) & TSN_SIGN_BIT;
-}
-
-static inline int TSN_lte(__u32 s, __u32 t)
-{
-	return ((s) == (t)) || (((s) - (t)) & TSN_SIGN_BIT);
-}
+#define TSN_lte(a,b)	\
+	(typecheck(__u32, a) && \
+	 typecheck(__u32, b) && \
+	 ((__s32)((a) - (b)) <= 0))
 
 /* Compare two SSNs */
-
-/*
- * RFC 2960
- *  1.6 Serial Number Arithmetic
- *
- * Comparisons and arithmetic on Stream Sequence Numbers in this document
- * SHOULD use Serial Number Arithmetic as defined in [RFC1982] where
- * SERIAL_BITS = 16.
- */
-enum {
-	SSN_SIGN_BIT = (1<<15)
-};
-
-static inline int SSN_lt(__u16 s, __u16 t)
-{
-	return ((s) - (t)) & SSN_SIGN_BIT;
-}
-
-static inline int SSN_lte(__u16 s, __u16 t)
-{
-	return ((s) == (t)) || (((s) - (t)) & SSN_SIGN_BIT);
-}
-
-/*
- * ADDIP 3.1.1
- * The valid range of Serial Number is from 0 to 4294967295 (2**32 - 1). Serial
- * Numbers wrap back to 0 after reaching 4294967295.
- */
-enum {
-	ADDIP_SERIAL_SIGN_BIT = (1<<31)
-};
-
-static inline int ADDIP_SERIAL_gte(__u32 s, __u32 t)
-{
-	return ((s) == (t)) || (((t) - (s)) & ADDIP_SERIAL_SIGN_BIT);
-}
+#define SSN_lt(a,b)		\
+	(typecheck(__u16, a) && \
+	 typecheck(__u16, b) && \
+	 ((__s16)((a) - (b)) < 0))
+
+/* ADDIP 3.1.1 */
+#define ADDIP_SERIAL_gte(a,b)	\
+	(typecheck(__u32, a) && \
+	 typecheck(__u32, b) && \
+	 ((__s32)((b) - (a)) <= 0))
 
 /* Check VTAG of the packet matches the sender's own tag. */
 static inline int
diff --git a/net/sctp/outqueue.c b/net/sctp/outqueue.c
index 8c3f446d965c030376d0cfafd2c64b9a946d2cc1..3ec6da8bbb5360187007935838717885c97f9e91 100644
--- a/net/sctp/outqueue.c
+++ b/net/sctp/outqueue.c
@@ -1719,7 +1719,7 @@ static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
 {
 	int i;
 	sctp_sack_variable_t *frags;
-	__u16 gap;
+	__u16 tsn_offset, blocks;
 	__u32 ctsn = ntohl(sack->cum_tsn_ack);
 
 	if (TSN_lte(tsn, ctsn))
@@ -1738,10 +1738,11 @@ static int sctp_acked(struct sctp_sackhdr *sack, __u32 tsn)
 	 */
 
 	frags = sack->variable;
-	gap = tsn - ctsn;
-	for (i = 0; i < ntohs(sack->num_gap_ack_blocks); ++i) {
-		if (TSN_lte(ntohs(frags[i].gab.start), gap) &&
-		    TSN_lte(gap, ntohs(frags[i].gab.end)))
+	blocks = ntohs(sack->num_gap_ack_blocks);
+	tsn_offset = tsn - ctsn;
+	for (i = 0; i < blocks; ++i) {
+		if (tsn_offset >= ntohs(frags[i].gab.start) &&
+		    tsn_offset <= ntohs(frags[i].gab.end))
 			goto pass;
 	}