[Git][NTPsec/ntpsec][master] include/ntp.h: align V4/V6_SIZEOF_RESTRICT_U strides

[Matt Selsky (@selsky)]

Matt Selsky pushed to branch master at NTPsec / ntpsec


Commits:
41aab4b3 by Matt Selsky at 2026-10-09T02:29:39-04:00
include/ntp.h: align V4/V6_SIZEOF_RESTRICT_U strides

The macros computed unaligned strides (28 and 52 bytes) for arrays of
restrict_u. The struct's alignment requirement (8 bytes on 64-bit platforms,
driven by the uint64_t hitcount field) was not preserved between consecutive
entries. On x86 this was silent UB; on strict-alignment platforms it would
SIGBUS. Round both sizes up to __alignof__(restrict_u) so the rounding adapts
if a stricter-aligned member is ever added.

Found with UBSan in test_ntpd.

- - - - -


1 changed file:

- include/ntp.h


Changes:

=====================================
include/ntp.h
=====================================
@@ -667,10 +667,14 @@ struct restrict_u_tag {
 		res_addr6 v6;
 	} u;
 };
-#define	V4_SIZEOF_RESTRICT_U	(offsetof(restrict_u, u)	\
-				 + sizeof(res_addr4))
-#define	V6_SIZEOF_RESTRICT_U	(offsetof(restrict_u, u)	\
-				 + sizeof(res_addr6))
+/* Round up to preserve restrict_u alignment when these sizes are used as
+ * the stride between consecutive entries in an emalloc'd array. */
+#define	V4_SIZEOF_RESTRICT_U	((offsetof(restrict_u, u) + sizeof(res_addr4) \
+				  + __alignof__(restrict_u) - 1)	\
+				 & ~(__alignof__(restrict_u) - 1))
+#define	V6_SIZEOF_RESTRICT_U	((offsetof(restrict_u, u) + sizeof(res_addr6) \
+				  + __alignof__(restrict_u) - 1)	\
+				 & ~(__alignof__(restrict_u) - 1))
 
 /* pythonize-header: stop ignoring */
 



View it on GitLab: https://gitlab.com/NTPsec/ntpsec/-/commit/41aab4b342457f76e700232f01e2d3a1b7bebbc5

-- 
View it on GitLab: https://gitlab.com/NTPsec/ntpsec/-/commit/41aab4b342457f76e700232f01e2d3a1b7bebbc5
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