execve

Linux 6.18.37 LTS: fs/exec.c
Linux 6.18.37 LTS: fs/binfmt_elf.c
Linux 6.18.37 LTS: include/linux/binfmts.h

	 *
	 * In the case of argc = 0, make sure there is space for adding a
	 * empty string (which will bump argc to 1), to ensure confused
	 * userspace programs don't start processing from argv[1], thinking
	 * argc can never be 0, to keep them from walking envp by accident.
	 * See do_execveat_common().
	 */
	ptr_size = (max(bprm->argc, 1) + bprm->envc) * sizeof(void *);
	if (limit <= ptr_size)
		return -E2BIG;
	limit -= ptr_size;

	bprm->argmin = bprm->p - limit;
	return 0;
}

/*
 * 'copy_strings()' copies argument/environment strings from the old
 * processes's memory to the new process's stack.  The call to get_user_pages()
 * ensures the destination page is created and not swapped out.
 */
static int copy_strings(int argc, struct user_arg_ptr argv,
			struct linux_binprm *bprm)
{
	struct page *kmapped_page = NULL;
	char *kaddr = NULL;
	unsigned long kpos = 0;
	int ret;

	while (argc-- > 0) {
		const char __user *str;
		int len;
		unsigned long pos;

		ret = -EFAULT;
		str = get_user_arg_ptr(argv, argc);
		if (IS_ERR(str))
			goto out;

		len = strnlen_user(str, MAX_ARG_STRLEN);

}

/*
 * sys_execve() executes a new program.
 */
static int bprm_execve(struct linux_binprm *bprm,
		       int fd, struct filename *filename, int flags)
{
	struct file *file;
	int retval;

	retval = prepare_bprm_creds(bprm);
	if (retval)
		return retval;

	/*
	 * Check for unsafe execution states before exec_binprm(), which
	 * will call back into begin_new_exec(), into bprm_creds_from_file(),
	 * where setuid-ness is evaluated.
	 */
	check_unsafe_exec(bprm);
	current->in_execve = 1;
	sched_mm_cid_before_execve(current);

	file = do_open_execat(fd, filename, flags);
	retval = PTR_ERR(file);
	if (IS_ERR(file))
		goto out_unmark;

	sched_exec();

	bprm->file = file;
	/*
	 * Record that a name derived from an O_CLOEXEC fd will be
	 * inaccessible after exec.  This allows the code in exec to
	 * choose to fail when the executable is not mmaped into the
	 * interpreter and an open file descriptor is not passed to
	 * the interpreter.  This makes for a better user experience
	 * than having the interpreter start and then immediately fail
	 * when it finds the executable is inaccessible.