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 inline bool spacetab(char c) { return c == ' ' || c == '\t'; }
18static inline char *next_non_spacetab(char *first, const char *last)
19{
20 for (; first <= last; first++)
21 if (!spacetab(*first))
22 return first;
23 return NULL;
24}
25static inline char *next_terminator(char *first, const char *last)
26{
27 for (; first <= last; first++)
28 if (spacetab(*first) || !*first)
29 return first;
30 return NULL;
31}
32
33static int load_script(struct linux_binprm *bprm)
34{
35 const char *i_arg, *i_name;
36 char *cp, *buf_end;
37 struct file *file;
38 int retval;
39
40 /* Not ours to exec if we don't start with "#!". */
41 if ((bprm->buf[0] != '#') || (bprm->buf[1] != '!'))
42 return -ENOEXEC;
43
44 /*
45 * If the script filename will be inaccessible after exec, typically
46 * because it is a "/dev/fd/<fd>/.." path against an O_CLOEXEC fd, give
47 * up now (on the assumption that the interpreter will want to load
48 * this file).
49 */
50 if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE)
51 return -ENOENT;
52
53 /* Release since we are not mapping a binary into memory. */
54 allow_write_access(bprm->file);
55 fput(bprm->file);
56 bprm->file = NULL;
57
58 /*
59 * This section handles parsing the #! line into separate
60 * interpreter path and argument strings. We must be careful
61 * because bprm->buf is not yet guaranteed to be NUL-terminated
62 * (though the buffer will have trailing NUL padding when the
63 * file size was smaller than the buffer size).
64 *
65 * We do not want to exec a truncated interpreter path, so either
66 * we find a newline (which indicates nothing is truncated), or
67 * we find a space/tab/NUL after the interpreter path (which
68 * itself may be preceded by spaces/tabs). Truncating the
69 * arguments is fine: the interpreter can re-read the script to
70 * parse them on its own.
71 */
72 buf_end = bprm->buf + sizeof(bprm->buf) - 1;
73 cp = strnchr(bprm->buf, sizeof(bprm->buf), '\n');
74 if (!cp) {
75 cp = next_non_spacetab(bprm->buf + 2, buf_end);
76 if (!cp)
77 return -ENOEXEC; /* Entire buf is spaces/tabs */
78 /*
79 * If there is no later space/tab/NUL we must assume the
80 * interpreter path is truncated.
81 */
82 if (!next_terminator(cp, buf_end))
83 return -ENOEXEC;
84 cp = buf_end;
85 }
86 /* NUL-terminate the buffer and any trailing spaces/tabs. */
87 *cp = '\0';
88 while (cp > bprm->buf) {
89 cp--;
90 if ((*cp == ' ') || (*cp == '\t'))
91 *cp = '\0';
92 else
93 break;
94 }
95 for (cp = bprm->buf+2; (*cp == ' ') || (*cp == '\t'); cp++);
96 if (*cp == '\0')
97 return -ENOEXEC; /* No interpreter name found */
98 i_name = cp;
99 i_arg = NULL;
100 for ( ; *cp && (*cp != ' ') && (*cp != '\t'); cp++)
101 /* nothing */ ;
102 while ((*cp == ' ') || (*cp == '\t'))
103 *cp++ = '\0';
104 if (*cp)
105 i_arg = cp;
106 /*
107 * OK, we've parsed out the interpreter name and
108 * (optional) argument.
109 * Splice in (1) the interpreter's name for argv[0]
110 * (2) (optional) argument to interpreter
111 * (3) filename of shell script (replace argv[0])
112 *
113 * This is done in reverse order, because of how the
114 * user environment and arguments are stored.
115 */
116 retval = remove_arg_zero(bprm);
117 if (retval)
118 return retval;
119 retval = copy_strings_kernel(1, &bprm->interp, bprm);
120 if (retval < 0)
121 return retval;
122 bprm->argc++;
123 if (i_arg) {
124 retval = copy_strings_kernel(1, &i_arg, bprm);
125 if (retval < 0)
126 return retval;
127 bprm->argc++;
128 }
129 retval = copy_strings_kernel(1, &i_name, bprm);
130 if (retval)
131 return retval;
132 bprm->argc++;
133 retval = bprm_change_interp(i_name, bprm);
134 if (retval < 0)
135 return retval;
136
137 /*
138 * OK, now restart the process with the interpreter's dentry.
139 */
140 file = open_exec(i_name);
141 if (IS_ERR(file))
142 return PTR_ERR(file);
143
144 bprm->file = file;
145 retval = prepare_binprm(bprm);
146 if (retval < 0)
147 return retval;
148 return search_binary_handler(bprm);
149}
150
151static struct linux_binfmt script_format = {
152 .module = THIS_MODULE,
153 .load_binary = load_script,
154};
155
156static int __init init_script_binfmt(void)
157{
158 register_binfmt(&script_format);
159 return 0;
160}
161
162static void __exit exit_script_binfmt(void)
163{
164 unregister_binfmt(&script_format);
165}
166
167core_initcall(init_script_binfmt);
168module_exit(exit_script_binfmt);
169MODULE_LICENSE("GPL");
170