// SPDX-License-Identifier: GPL-2.0-only/* *  linux/fs/binfmt_script.c * *  Copyright (C) 1996  Martin von Löwis *  original #!-checking implemented by tytso. */ #include <linux/module.h>#include <linux/string.h>#include <linux/stat.h>#include <linux/binfmts.h>#include <linux/init.h>#include <linux/file.h>#include <linux/err.h>#include <linux/fs.h> static inline bool spacetab(char c) { return c == ' ' || c == '\t'; }static inline const char *next_non_spacetab(const char *first, const char *last){	for (; first <= last; first++)		if (!spacetab(*first))			return first;	return NULL;}static inline const char *next_terminator(const char *first, const char *last){	for (; first <= last; first++)		if (spacetab(*first) || !*first)			return first;	return NULL;} static int load_script(struct linux_binprm *bprm){	const char *i_name, *i_sep, *i_arg, *i_end, *buf_end;	struct file *file;	int retval; 	/* Not ours to exec if we don't start with "#!". */	if ((bprm->buf[0] != '#') || (bprm->buf[1] != '!'))		return -ENOEXEC; 	/*	 * This section handles parsing the #! line into separate	 * interpreter path and argument strings. We must be careful	 * because bprm->buf is not yet guaranteed to be NUL-terminated	 * (though the buffer will have trailing NUL padding when the	 * file size was smaller than the buffer size).	 *	 * We do not want to exec a truncated interpreter path, so either	 * we find a newline (which indicates nothing is truncated), or	 * we find a space/tab/NUL after the interpreter path (which	 * itself may be preceded by spaces/tabs). Truncating the	 * arguments is fine: the interpreter can re-read the script to	 * parse them on its own.	 */	buf_end = bprm->buf + sizeof(bprm->buf) - 1;	i_end = strnchr(bprm->buf, sizeof(bprm->buf), '\n');	if (!i_end) {		i_end = next_non_spacetab(bprm->buf + 2, buf_end);		if (!i_end)			return -ENOEXEC; /* Entire buf is spaces/tabs */		/*		 * If there is no later space/tab/NUL we must assume the		 * interpreter path is truncated.		 */		if (!next_terminator(i_end, buf_end))			return -ENOEXEC;		i_end = buf_end;	}	/* Trim any trailing spaces/tabs from i_end */	while (spacetab(i_end[-1]))		i_end--; 	/* Skip over leading spaces/tabs */	i_name = next_non_spacetab(bprm->buf+2, i_end);	if (!i_name || (i_name == i_end))		return -ENOEXEC; /* No interpreter name found */ 	/* Is there an optional argument? */	i_arg = NULL;	i_sep = next_terminator(i_name, i_end);	if (i_sep && (*i_sep != '\0'))		i_arg = next_non_spacetab(i_sep, i_end); 	/*	 * If the script filename will be inaccessible after exec, typically	 * because it is a "/dev/fd/<fd>/.." path against an O_CLOEXEC fd, give	 * up now (on the assumption that the interpreter will want to load	 * this file).	 */	if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE)		return -ENOENT; 	/*	 * OK, we've parsed out the interpreter name and	 * (optional) argument.	 * Splice in (1) the interpreter's name for argv[0]	 *           (2) (optional) argument to interpreter	 *           (3) filename of shell script (replace argv[0])	 *	 * This is done in reverse order, because of how the	 * user environment and arguments are stored.	 */	retval = remove_arg_zero(bprm);	if (retval)		return retval;	retval = copy_string_kernel(bprm->interp, bprm);	if (retval < 0)		return retval;	bprm->argc++;	*((char *)i_end) = '\0';	if (i_arg) {		*((char *)i_sep) = '\0';		retval = copy_string_kernel(i_arg, bprm);		if (retval < 0)			return retval;		bprm->argc++;	}	retval = copy_string_kernel(i_name, bprm);	if (retval)		return retval;	bprm->argc++;	retval = bprm_change_interp(i_name, bprm);	if (retval < 0)		return retval; 	/*	 * OK, now restart the process with the interpreter's dentry.	 */	file = open_exec(i_name);	if (IS_ERR(file))		return PTR_ERR(file); 	bprm->interpreter = file;	return 0;} static struct linux_binfmt script_format = {	.module		= THIS_MODULE,	.load_binary	= load_script,}; static int __init init_script_binfmt(void){	register_binfmt(&script_format);	return 0;} static void __exit exit_script_binfmt(void){	unregister_binfmt(&script_format);} core_initcall(init_script_binfmt);module_exit(exit_script_binfmt);MODULE_LICENSE("GPL");