vboxsf: Replace all non-returning strlcpy with strscpy

strlcpy() reads the entire source buffer first.
This read may exceed the destination size limit.
This is both inefficient and can lead to linear read
overflows if a source string is not NUL-terminated [1].
In an effort to remove strlcpy() completely [2], replace
strlcpy() here with strscpy().
No return values were used, so direct replacement is safe.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
[2] https://github.com/KSPP/linux/issues/89

Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20230510211146.3486600-1-azeemshaikh38@gmail.com

fs/vboxsf/super.c

@@ -176,7 +176,7 @@ static int vboxsf_fill_super(struct super_block *sb, struct fs_context *fc)
 	}
 	folder_name->size = size;
 	folder_name->length = size - 1;
-	strlcpy(folder_name->string.utf8, fc->source, size);
+	strscpy(folder_name->string.utf8, fc->source, size);
 	err = vboxsf_map_folder(folder_name, &sbi->root);
 	kfree(folder_name);
 	if (err) {