[PATCH] ACPI: OSI: refactor deprecated strncpy

[Justin Stitt]

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

We know `osi->string` is a NUL-terminated string due to its eventual use
in `acpi_install_interface()` and `acpi_remove_interface()` which expect
a `acpi_string` which has been specifically typedef'd as:
|  typedef char *acpi_string;	/* Null terminated ASCII string */

... and which also has other string functions used on it like `strlen`.
Furthermore, padding is not needed in this instance either.

Due to the reasoning above a suitable replacement is `strscpy` [2] since
it guarantees NUL-termination on the destination buffer and doesn't
unnecessarily NUL-pad.

While there is unlikely to be a buffer overread (or other related bug)
in this case, we should still favor a more robust and less ambiguous
interface.

Link: https://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
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Justin Stitt <justinstitt@xxxxxxxxxx>
---
Note: build-tested
---
 drivers/acpi/osi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/acpi/osi.c b/drivers/acpi/osi.c
index d4405e1ca9b9..df9328c850bd 100644
--- a/drivers/acpi/osi.c
+++ b/drivers/acpi/osi.c
@@ -110,7 +110,7 @@ void __init acpi_osi_setup(char *str)
 			break;
 		} else if (osi->string[0] == '\0') {
 			osi->enable = enable;
-			strncpy(osi->string, str, OSI_STRING_LENGTH_MAX);
+			strscpy(osi->string, str, OSI_STRING_LENGTH_MAX);
 			break;
 		}
 	}

---
base-commit: 2dde18cd1d8fac735875f2e4987f11817cc0bc2c
change-id: 20230911-strncpy-drivers-acpi-osi-c-c801b7427987

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