On Mon, Jan 12, 2026 at 08:22:36PM +0800, Fushuai Wang wrote:

quoted

strncpy_from_user() succeeds even if userspace data does not contain a
nul. Then it reads length bytes.

Yes, but if there is no NUL byte in the user buf, whether you use
strncpy_from_user() or copy_from_user(), you need to manually add
a '\0' in the kernel buf to ensure it is properly NUL-terminated.

This looks like a bunch of churn to save a "= \0" line.

The more important question, IMO, would be whether there are cases in the
kernel which *miss* a NUL termination, audit them and fix them.

That'll give you a better idea whether such a *_nul() helper is even needed.

Because converting only a handful of obvious places in the face of thousands
of copy_from_user() invocations in the kernel is not doing anything useful.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette