x86/platform/uv: Refactor code using deprecated strncpy() interface to use strscpy()

`strncpy` is deprecated for use on NUL-terminated destination strings [1].

A suitable replacement is `strscpy` [2] due to the fact that it
guarantees NUL-termination on its destination buffer argument which is
_not_ the case for `strncpy`!

In this case, it means we can drop the `...-1` from:
|       strncpy(to, from, len-1);

as well as remove the comment mentioning NUL-termination as `strscpy`
implicitly grants us this behavior.

There should be no functional change as I don't believe the padding from
`strncpy` is needed here. If it turns out that the padding is necessary
we should use `strscpy_pad` as a direct replacement.

Signed-off-by: Justin Stitt <justinstitt@google.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Dimitri Sivanich <sivanich@hpe.com>
Link: www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings[1]
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html
Link: https://github.com/KSPP/linux/issues/90
Link: https://lore.kernel.org/r/20230822-strncpy-arch-x86-kernel-apic-x2apic_uv_x-v1-1-91d681d0b3f3@google.com

diff --git a/arch/x86/kernel/apic/x2apic_uv_x.c b/arch/x86/kernel/apic/x2apic_uv_x.c
index d9384d5b4b8e93093323ed299a46923a7a913b2f..b524dee1cbbbc89c34504c5107f472efe1c407d2 100644 (file)
--- a/arch/x86/kernel/apic/x2apic_uv_x.c
+++ b/arch/x86/kernel/apic/x2apic_uv_x.c
@@ -294,8 +294,7 @@ static void __init early_get_apic_socketid_shift(void)
 
 static void __init uv_stringify(int len, char *to, char *from)
 {
-       /* Relies on 'to' being NULL chars so result will be NULL terminated */
-       strncpy(to, from, len-1);
+       strscpy(to, from, len);
 
        /* Trim trailing spaces */
        (void)strim(to);
@@ -1013,7 +1012,7 @@ static void __init calc_mmioh_map(enum mmioh_arch index,
 
        /* One (UV2) mapping */
        if (index == UV2_MMIOH) {
-               strncpy(id, "MMIOH", sizeof(id));
+               strscpy(id, "MMIOH", sizeof(id));
                max_io = max_pnode;
                mapped = 0;
                goto map_exit;