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

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The use of the 2-argument `strscpy` macro in `skel_internal.h` breaks compilation of light skeletons for out-of-tree kernel modules on kernels older than 6.8.
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commit 056f88b29a55562ae428a73e0cbb771aa82987a6
Author: Kees Cook <kees@kernel.org>

libbpf: Use strscpy() in kernel code for skel_map_create()

This commit replaces a deprecated strncpy() call with strscpy() in
skel_map_create() when building for the kernel, leaving the user-space
version unchanged.

Link: https://github.com/KSPP/linux/issues/90 [1]

> diff --git a/tools/lib/bpf/skel_internal.h b/tools/lib/bpf/skel_internal.h
> --- 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)

Does this break backwards compatibility for out-of-tree kernel modules using
generated light skeletons on kernels older than 6.8?

The 2-argument strscpy macro was introduced in Linux 6.8. Older kernels like
6.1 LTS and 6.6 LTS only provide the 3-argument version:
ssize_t strscpy(char *dest, const char *src, size_t count).

Compiling this generated skeleton code on older kernels will result in a
compiler error due to too few arguments.

Would it be better to use the 3-argument version here instead?
strscpy(attr.map_name, map_name, sizeof(attr.map_name))

> +		return -EINVAL;
> +#else
>  	strncpy(attr.map_name, map_name, sizeof(attr.map_name));
> +#endif

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Sashiko AI review · https://sashiko.dev/#/patchset/20260513050806.do.620-kees@kernel.org?part=1