Merge "Disallow pre-T use of userspace writable bpf map arrays with more than 1 element."
diff --git a/staticlibs/native/bpf_headers/include/bpf/bpf_helpers.h b/staticlibs/native/bpf_headers/include/bpf/bpf_helpers.h
index 2d51702..56bc7d0 100644
--- a/staticlibs/native/bpf_headers/include/bpf/bpf_helpers.h
+++ b/staticlibs/native/bpf_headers/include/bpf/bpf_helpers.h
@@ -151,6 +151,23 @@
__attribute__ ((section(".maps." #name), used)) \
____btf_map_##name = { }
+/* There exist buggy kernels with pre-T OS, that due to
+ * kernel patch "[ALPS05162612] bpf: fix ubsan error"
+ * do not support userspace writes into non-zero index of bpf map arrays.
+ *
+ * We use this assert to prevent us from being able to define such a map.
+ */
+
+#ifdef THIS_BPF_PROGRAM_IS_FOR_TEST_PURPOSES_ONLY
+#define BPF_MAP_ASSERT_OK(type, entries, mode)
+#elif BPFLOADER_MIN_VER >= BPFLOADER_T_BETA3_VERSION
+#define BPF_MAP_ASSERT_OK(type, entries, mode)
+#else
+#define BPF_MAP_ASSERT_OK(type, entries, mode) \
+ _Static_assert(((type) != BPF_MAP_TYPE_ARRAY) || ((entries) <= 1) || !((mode) & 0222), \
+ "Writable arrays with more than 1 element not supported on pre-T devices.")
+#endif
+
/* type safe macro to declare a map and related accessor functions */
#define DEFINE_BPF_MAP_EXT(the_map, TYPE, KeyType, ValueType, num_entries, usr, grp, md, \
selinux, pindir, share) \
@@ -171,6 +188,7 @@
.pin_subdir = pindir, \
.shared = share, \
}; \
+ BPF_MAP_ASSERT_OK(BPF_MAP_TYPE_##TYPE, (num_entries), (md)); \
BPF_ANNOTATE_KV_PAIR(the_map, KeyType, ValueType); \
\
static inline __always_inline __unused ValueType* bpf_##the_map##_lookup_elem( \