[PATCH v5] libbpf: Use strscpy() in kernel code for skel_map_create()

[Kees Cook <kees@kernel.org>]

Linux has deprecated[1] strncpy(), and the use in skel_map_create()
is best replaced with strscpy(). Since we still need to build this
file in userspace, leave the strncpy() in place in that case. This
is the last use of strncpy() in the kernel.

Link: https://github.com/KSPP/linux/issues/90 [1]
Signed-off-by: Kees Cook <kees@kernel.org>
---
 v5: Just ifdef for the kernel and use strscpy() there (Alexei)
 v4: https://lore.kernel.org/lkml/20260401001130.it.781-kees@kernel.org/
 v3: https://lore.kernel.org/lkml/20260324161605.make.168-kees@kernel.org/
 v2: https://lore.kernel.org/lkml/20260324053036.it.906-kees@kernel.org/
 v1: https://lore.kernel.org/lkml/20260324040535.work.851-kees@kernel.org/
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: sun jian <sun.jian.kdev@gmail.com>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Eduard Zingerman <eddyz87@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Martin KaFai Lau <martin.lau@linux.dev>
Cc: Song Liu <song@kernel.org>
Cc: Yonghong Song <yonghong.song@linux.dev>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: KP Singh <kpsingh@kernel.org>
Cc: Stanislav Fomichev <sdf@fomichev.me>
Cc: Hao Luo <haoluo@google.com>
Cc: <bpf@vger.kernel.org>
---
 tools/lib/bpf/skel_internal.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tools/lib/bpf/skel_internal.h b/tools/lib/bpf/skel_internal.h
index 6a8f5c7a02eb..74503d358bc8 100644
--- a/tools/lib/bpf/skel_internal.h
+++ b/tools/lib/bpf/skel_internal.h
@@ -243,7 +243,12 @@ static inline int skel_map_create(enum bpf_map_type map_type,
 	attr.excl_prog_hash = (unsigned long) excl_prog_hash;
 	attr.excl_prog_hash_size = excl_prog_hash_sz;
 
+#ifdef __KERNEL__
+	if (strscpy(attr.map_name, map_name) < 0)
+		return -EINVAL;
+#else
 	strncpy(attr.map_name, map_name, sizeof(attr.map_name));
+#endif
 	attr.key_size = key_size;
 	attr.value_size = value_size;
 	attr.max_entries = max_entries;
-- 
2.34.1