[PATCH] x86/platform/uv: refactor deprecated strncpy

[Justin Stitt]

`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.

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 [2]
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@xxxxxxxxxxxxxxx
Signed-off-by: Justin Stitt <justinstitt@xxxxxxxxxx>
---
Note: build-tested only
---
 arch/x86/kernel/apic/x2apic_uv_x.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/apic/x2apic_uv_x.c b/arch/x86/kernel/apic/x2apic_uv_x.c
index d9384d5b4b8e..b524dee1cbbb 100644
--- 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;

---
base-commit: 706a741595047797872e669b3101429ab8d378ef
change-id: 20230822-strncpy-arch-x86-kernel-apic-x2apic_uv_x-e51e08a5fbcd

Best regards,
--
Justin Stitt <justinstitt@xxxxxxxxxx>