1/*
2 *  linux/fs/binfmt_script.c
3 *
4 *  Copyright (C) 1996  Martin von Löwis
5 *  original #!-checking implemented by tytso.
6 */
7
8#include <linux/module.h>
9#include <linux/string.h>
10#include <linux/stat.h>
11#include <linux/binfmts.h>
12#include <linux/init.h>
13#include <linux/file.h>
14#include <linux/err.h>
15#include <linux/fs.h>
16
17static int load_script(struct linux_binprm *bprm)
18{
19	const char *i_arg, *i_name;
20	char *cp;
21	struct file *file;
22	char interp[BINPRM_BUF_SIZE];
23	int retval;
24
25	if ((bprm->buf[0] != '#') || (bprm->buf[1] != '!'))
26		return -ENOEXEC;
27
28	/*
29	 * If the script filename will be inaccessible after exec, typically
30	 * because it is a "/dev/fd/<fd>/.." path against an O_CLOEXEC fd, give
31	 * up now (on the assumption that the interpreter will want to load
32	 * this file).
33	 */
34	if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE)
35		return -ENOENT;
36
37	/*
38	 * This section does the #! interpretation.
39	 * Sorta complicated, but hopefully it will work.  -TYT
40	 */
41
42	allow_write_access(bprm->file);
43	fput(bprm->file);
44	bprm->file = NULL;
45
46	bprm->buf[BINPRM_BUF_SIZE - 1] = '\0';
47	if ((cp = strchr(bprm->buf, '\n')) == NULL)
48		cp = bprm->buf+BINPRM_BUF_SIZE-1;
49	*cp = '\0';
50	while (cp > bprm->buf) {
51		cp--;
52		if ((*cp == ' ') || (*cp == '\t'))
53			*cp = '\0';
54		else
55			break;
56	}
57	for (cp = bprm->buf+2; (*cp == ' ') || (*cp == '\t'); cp++);
58	if (*cp == '\0')
59		return -ENOEXEC; /* No interpreter name found */
60	i_name = cp;
61	i_arg = NULL;
62	for ( ; *cp && (*cp != ' ') && (*cp != '\t'); cp++)
63		/* nothing */ ;
64	while ((*cp == ' ') || (*cp == '\t'))
65		*cp++ = '\0';
66	if (*cp)
67		i_arg = cp;
68	strcpy (interp, i_name);
69	/*
70	 * OK, we've parsed out the interpreter name and
71	 * (optional) argument.
72	 * Splice in (1) the interpreter's name for argv[0]
73	 *           (2) (optional) argument to interpreter
74	 *           (3) filename of shell script (replace argv[0])
75	 *
76	 * This is done in reverse order, because of how the
77	 * user environment and arguments are stored.
78	 */
79	retval = remove_arg_zero(bprm);
80	if (retval)
81		return retval;
82	retval = copy_strings_kernel(1, &bprm->interp, bprm);
83	if (retval < 0) return retval;
84	bprm->argc++;
85	if (i_arg) {
86		retval = copy_strings_kernel(1, &i_arg, bprm);
87		if (retval < 0) return retval;
88		bprm->argc++;
89	}
90	retval = copy_strings_kernel(1, &i_name, bprm);
91	if (retval) return retval;
92	bprm->argc++;
93	retval = bprm_change_interp(interp, bprm);
94	if (retval < 0)
95		return retval;
96
97	/*
98	 * OK, now restart the process with the interpreter's dentry.
99	 */
100	file = open_exec(interp);
101	if (IS_ERR(file))
102		return PTR_ERR(file);
103
104	bprm->file = file;
105	retval = prepare_binprm(bprm);
106	if (retval < 0)
107		return retval;
108	return search_binary_handler(bprm);
109}
110
111static struct linux_binfmt script_format = {
112	.module		= THIS_MODULE,
113	.load_binary	= load_script,
114};
115
116static int __init init_script_binfmt(void)
117{
118	register_binfmt(&script_format);
119	return 0;
120}
121
122static void __exit exit_script_binfmt(void)
123{
124	unregister_binfmt(&script_format);
125}
126
127core_initcall(init_script_binfmt);
128module_exit(exit_script_binfmt);
129MODULE_LICENSE("GPL");
130