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
spacetab(char c)17 static inline bool spacetab(char c) { return c == ' ' || c == '\t'; }
next_non_spacetab(char * first,const char * last)18 static 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 }
next_terminator(char * first,const char * last)25 static 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
load_script(struct linux_binprm * bprm)33 static 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 char interp[BINPRM_BUF_SIZE];
39 int retval;
40
41 /* Not ours to exec if we don't start with "#!". */
42 if ((bprm->buf[0] != '#') || (bprm->buf[1] != '!'))
43 return -ENOEXEC;
44
45 /*
46 * If the script filename will be inaccessible after exec, typically
47 * because it is a "/dev/fd/<fd>/.." path against an O_CLOEXEC fd, give
48 * up now (on the assumption that the interpreter will want to load
49 * this file).
50 */
51 if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE)
52 return -ENOENT;
53
54 /* Release since we are not mapping a binary into memory. */
55 allow_write_access(bprm->file);
56 fput(bprm->file);
57 bprm->file = NULL;
58
59 /*
60 * This section handles parsing the #! line into separate
61 * interpreter path and argument strings. We must be careful
62 * because bprm->buf is not yet guaranteed to be NUL-terminated
63 * (though the buffer will have trailing NUL padding when the
64 * file size was smaller than the buffer size).
65 *
66 * We do not want to exec a truncated interpreter path, so either
67 * we find a newline (which indicates nothing is truncated), or
68 * we find a space/tab/NUL after the interpreter path (which
69 * itself may be preceded by spaces/tabs). Truncating the
70 * arguments is fine: the interpreter can re-read the script to
71 * parse them on its own.
72 */
73 buf_end = bprm->buf + sizeof(bprm->buf) - 1;
74 cp = strnchr(bprm->buf, sizeof(bprm->buf), '\n');
75 if (!cp) {
76 cp = next_non_spacetab(bprm->buf + 2, buf_end);
77 if (!cp)
78 return -ENOEXEC; /* Entire buf is spaces/tabs */
79 /*
80 * If there is no later space/tab/NUL we must assume the
81 * interpreter path is truncated.
82 */
83 if (!next_terminator(cp, buf_end))
84 return -ENOEXEC;
85 cp = buf_end;
86 }
87 /* NUL-terminate the buffer and any trailing spaces/tabs. */
88 *cp = '\0';
89 while (cp > bprm->buf) {
90 cp--;
91 if ((*cp == ' ') || (*cp == '\t'))
92 *cp = '\0';
93 else
94 break;
95 }
96 for (cp = bprm->buf+2; (*cp == ' ') || (*cp == '\t'); cp++);
97 if (*cp == '\0')
98 return -ENOEXEC; /* No interpreter name found */
99 i_name = cp;
100 i_arg = NULL;
101 for ( ; *cp && (*cp != ' ') && (*cp != '\t'); cp++)
102 /* nothing */ ;
103 while ((*cp == ' ') || (*cp == '\t'))
104 *cp++ = '\0';
105 if (*cp)
106 i_arg = cp;
107 strcpy (interp, i_name);
108 /*
109 * OK, we've parsed out the interpreter name and
110 * (optional) argument.
111 * Splice in (1) the interpreter's name for argv[0]
112 * (2) (optional) argument to interpreter
113 * (3) filename of shell script (replace argv[0])
114 *
115 * This is done in reverse order, because of how the
116 * user environment and arguments are stored.
117 */
118 retval = remove_arg_zero(bprm);
119 if (retval)
120 return retval;
121 retval = copy_strings_kernel(1, &bprm->interp, bprm);
122 if (retval < 0) return retval;
123 bprm->argc++;
124 if (i_arg) {
125 retval = copy_strings_kernel(1, &i_arg, bprm);
126 if (retval < 0) return retval;
127 bprm->argc++;
128 }
129 retval = copy_strings_kernel(1, &i_name, bprm);
130 if (retval) return retval;
131 bprm->argc++;
132 retval = bprm_change_interp(interp, bprm);
133 if (retval < 0)
134 return retval;
135
136 /*
137 * OK, now restart the process with the interpreter's dentry.
138 */
139 file = open_exec(interp);
140 if (IS_ERR(file))
141 return PTR_ERR(file);
142
143 bprm->file = file;
144 retval = prepare_binprm(bprm);
145 if (retval < 0)
146 return retval;
147 return search_binary_handler(bprm);
148 }
149
150 static struct linux_binfmt script_format = {
151 .module = THIS_MODULE,
152 .load_binary = load_script,
153 };
154
init_script_binfmt(void)155 static int __init init_script_binfmt(void)
156 {
157 register_binfmt(&script_format);
158 return 0;
159 }
160
exit_script_binfmt(void)161 static void __exit exit_script_binfmt(void)
162 {
163 unregister_binfmt(&script_format);
164 }
165
166 core_initcall(init_script_binfmt);
167 module_exit(exit_script_binfmt);
168 MODULE_LICENSE("GPL");
169