net: ip: 6lo: Fix undefined behavior reported by UBSAN

tpambor · dkalowsk · commit a760ba76b68f · 2025-06-03T21:32:54.000-07:00
htonl() and htons() take uint32_t/uint16_t as argument. Add the 'u' suffix
to constants to ensure the correct unsigned type is used and to avoid
undefined behavior if these functions are implemented as macros using
bit shifts.

Signed-off-by: Tim Pambor &lt;tim.pambor@codewrights.de&gt;
diff --git a/subsys/net/ip/6lo.c b/subsys/net/ip/6lo.c
@@ -128,8 +128,8 @@ static inline bool net_6lo_ll_prefix_padded_with_zeros(struct in6_addr *addr)
 
 static inline bool net_6lo_addr_16_bit_compressible(struct in6_addr *addr)
 {
-	return ((UNALIGNED_GET(&addr->s6_addr32[2]) == htonl(0xFF)) &&
-		 (UNALIGNED_GET(&addr->s6_addr16[6]) == htons(0xFE00)));
+	return ((UNALIGNED_GET(&addr->s6_addr32[2]) == htonl(0xFFu)) &&
+		 (UNALIGNED_GET(&addr->s6_addr16[6]) == htons(0xFE00u)));
 }
 
 static inline bool net_6lo_maddr_8_bit_compressible(struct in6_addr *addr)

Original file line number	Diff line number	Diff line change
`@@ -128,8 +128,8 @@ static inline bool net_6lo_ll_prefix_padded_with_zeros(struct in6_addr *addr)`
`128`	`128`
`129`	`129`	`static inline bool net_6lo_addr_16_bit_compressible(struct in6_addr *addr)`
`130`	`130`	`{`
`131`		`- return ((UNALIGNED_GET(&addr->s6_addr32[2]) == htonl(0xFF)) &&`
`132`		`- (UNALIGNED_GET(&addr->s6_addr16[6]) == htons(0xFE00)));`
	`131`	`+ return ((UNALIGNED_GET(&addr->s6_addr32[2]) == htonl(0xFFu)) &&`
	`132`	`+ (UNALIGNED_GET(&addr->s6_addr16[6]) == htons(0xFE00u)));`
`133`	`133`	`}`
`134`	`134`
`135`	`135`	`static inline bool net_6lo_maddr_8_bit_compressible(struct in6_addr *addr)`