ensure sv bodies are properly aligned

In some cases SV bodies don't include the same members as lower sv type
bodies, in particular, PVMG includes an NV member, while PVCV and
other specialised bodies don't include it, so PVMG can have a larger
alignment boundary.

This can result in a PVCV having a smaller alignment boundary than
PVMG, resulting in potential undefined behaviour if a member that
is common between PVCV and PVMG is accessed on an lesser aligned
PVCV pointer.

To avoid that, ensure allocation sizes described in bodies_by_type[]
account for NV (and IV) alignment requirements.

fixes #17668

1 files changed, 33 insertions, 16 deletions

diff --git a/sv.c b/sv.c
index 1c0cc743d0..cb02219af7 100644
--- a/sv.c
+++ b/sv.c
@@ -883,6 +883,23 @@ struct body_details {
     U32 arena_size;                 /* Size of arena to allocate */
 };
 
+#define ALIGNED_TYPE_NAME(name) name##_aligned
+#define ALIGNED_TYPE(name) 		\
+    typedef union { 	\
+        name align_me;				\
+        NV nv;				\
+        IV iv;				\
+    } ALIGNED_TYPE_NAME(name);
+
+ALIGNED_TYPE(regexp);
+ALIGNED_TYPE(XPVGV);
+ALIGNED_TYPE(XPVLV);
+ALIGNED_TYPE(XPVAV);
+ALIGNED_TYPE(XPVHV);
+ALIGNED_TYPE(XPVCV);
+ALIGNED_TYPE(XPVFM);
+ALIGNED_TYPE(XPVIO);
+
 #define HADNV FALSE
 #define NONV TRUE
 
@@ -971,48 +988,48 @@ static const struct body_details bodies_by_type[] = {
     { sizeof(XPVMG), copy_length(XPVMG, xnv_u), 0, SVt_PVMG, FALSE, HADNV,
       HASARENA, FIT_ARENA(0, sizeof(XPVMG)) },
 
-    { sizeof(regexp),
+    { sizeof(ALIGNED_TYPE_NAME(regexp)),
       sizeof(regexp),
       0,
       SVt_REGEXP, TRUE, NONV, HASARENA,
-      FIT_ARENA(0, sizeof(regexp))
+      FIT_ARENA(0, sizeof(ALIGNED_TYPE_NAME(regexp)))
     },
 
-    { sizeof(XPVGV), sizeof(XPVGV), 0, SVt_PVGV, TRUE, HADNV,
-      HASARENA, FIT_ARENA(0, sizeof(XPVGV)) },
+    { sizeof(ALIGNED_TYPE_NAME(XPVGV)), sizeof(XPVGV), 0, SVt_PVGV, TRUE, HADNV,
+      HASARENA, FIT_ARENA(0, sizeof(ALIGNED_TYPE_NAME(XPVGV))) },
     
-    { sizeof(XPVLV), sizeof(XPVLV), 0, SVt_PVLV, TRUE, HADNV,
-      HASARENA, FIT_ARENA(0, sizeof(XPVLV)) },
+    { sizeof(ALIGNED_TYPE_NAME(XPVLV)), sizeof(XPVLV), 0, SVt_PVLV, TRUE, HADNV,
+      HASARENA, FIT_ARENA(0, sizeof(ALIGNED_TYPE_NAME(XPVLV))) },
 
-    { sizeof(XPVAV),
+    { sizeof(ALIGNED_TYPE_NAME(XPVAV)),
       copy_length(XPVAV, xav_alloc),
       0,
       SVt_PVAV, TRUE, NONV, HASARENA,
-      FIT_ARENA(0, sizeof(XPVAV)) },
+      FIT_ARENA(0, sizeof(ALIGNED_TYPE_NAME(XPVAV))) },
 
-    { sizeof(XPVHV),
+    { sizeof(ALIGNED_TYPE_NAME(XPVHV)),
       copy_length(XPVHV, xhv_max),
       0,
       SVt_PVHV, TRUE, NONV, HASARENA,
-      FIT_ARENA(0, sizeof(XPVHV)) },
+      FIT_ARENA(0, sizeof(ALIGNED_TYPE_NAME(XPVHV))) },
 
-    { sizeof(XPVCV),
+    { sizeof(ALIGNED_TYPE_NAME(XPVCV)),
       sizeof(XPVCV),
       0,
       SVt_PVCV, TRUE, NONV, HASARENA,
-      FIT_ARENA(0, sizeof(XPVCV)) },
+      FIT_ARENA(0, sizeof(ALIGNED_TYPE_NAME(XPVCV))) },
 
-    { sizeof(XPVFM),
+    { sizeof(ALIGNED_TYPE_NAME(XPVFM)),
       sizeof(XPVFM),
       0,
       SVt_PVFM, TRUE, NONV, NOARENA,
-      FIT_ARENA(20, sizeof(XPVFM)) },
+      FIT_ARENA(20, sizeof(ALIGNED_TYPE_NAME(XPVFM))) },
 
-    { sizeof(XPVIO),
+    { sizeof(ALIGNED_TYPE_NAME(XPVIO)),
       sizeof(XPVIO),
       0,
       SVt_PVIO, TRUE, NONV, HASARENA,
-      FIT_ARENA(24, sizeof(XPVIO)) },
+      FIT_ARENA(24, sizeof(ALIGNED_TYPE_NAME(XPVIO))) },
 };
 
 #define new_body_allocated(sv_type)		\