`strncpy` is deprecated for use on NUL-terminated destination strings [1]. `efi_loader_signature` has space for 4 bytes. We are copying "Xen" (3 bytes) plus a NUL-byte which makes 4 total bytes. With that being said, there is currently not a bug with the current `strncpy()` implementation in terms of buffer overreads but we should favor a more robust string interface either way.
A suitable replacement is `strscpy` [2] due to the fact that it guarantees NUL-termination on the destination buffer while being functionally the same in this case. 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-harden...@vger.kernel.org Cc: Kees Cook <keesc...@chromium.org> Signed-off-by: Justin Stitt <justinst...@google.com> --- Note: build-tested --- arch/x86/xen/efi.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/xen/efi.c b/arch/x86/xen/efi.c index 863d0d6b3edc..7250d0e0e1a9 100644 --- a/arch/x86/xen/efi.c +++ b/arch/x86/xen/efi.c @@ -138,7 +138,7 @@ void __init xen_efi_init(struct boot_params *boot_params) if (efi_systab_xen == NULL) return; - strncpy((char *)&boot_params->efi_info.efi_loader_signature, "Xen", + strscpy((char *)&boot_params->efi_info.efi_loader_signature, "Xen", sizeof(boot_params->efi_info.efi_loader_signature)); boot_params->efi_info.efi_systab = (__u32)__pa(efi_systab_xen); boot_params->efi_info.efi_systab_hi = (__u32)(__pa(efi_systab_xen) >> 32); --- base-commit: 2dde18cd1d8fac735875f2e4987f11817cc0bc2c change-id: 20230911-strncpy-arch-x86-xen-efi-c-14292f5a79ee Best regards, -- Justin Stitt <justinst...@google.com>
