| 1 | |
| 2 | |
| 3 | * linux/fs/binfmt_script.c
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| 4 | *
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| 5 | * Copyright (C) 1996 Martin von Löwis
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| 6 | * original #!-checking implemented by tytso.
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| 7 |
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| 8 |
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| 9 | #include <linux/module.h>
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| 10 | #include <linux/string.h>
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| 11 | #include <linux/stat.h>
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| 12 | #include <linux/binfmts.h>
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| 13 | #include <linux/init.h>
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| 14 | #include <linux/file.h>
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| 15 | #include <linux/err.h>
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| 16 | #include <linux/fs.h>
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| 17 |
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| 18 | static inline bool spacetab(char c) { return c == ' ' || c == '\t'; }
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| 19 | static inline const char *next_non_spacetab(const char *first, const char *last)
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| 20 | {
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| 21 | for (; first <= last; first++)
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| 22 | if (!spacetab(*first))
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| 23 | return first;
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| 24 | return NULL;
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| 25 | }
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| 26 | static inline const char *next_terminator(const char *first, const char *last)
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| 27 | {
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| 28 | for (; first <= last; first++)
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| 29 | if (spacetab(*first) || !*first)
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| 30 | return first;
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| 31 | return NULL;
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| 32 | }
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| 33 |
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| 34 | static int load_script(struct linux_binprm *bprm)
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| 35 | {
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| 36 | const char *i_name, *i_sep, *i_arg, *i_end, *buf_end;
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| 37 | struct file *file;
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| 38 | int retval;
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| 39 |
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| 40 |
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| 41 | if ((bprm->buf[0] != '#') || (bprm->buf[1] != '!'))
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| 42 | return -ENOEXEC;
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| 43 |
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| 44 | |
| 45 | * This section handles parsing the #! line into separate
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| 46 | * interpreter path and argument strings. We must be careful
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| 47 | * because bprm->buf is not yet guaranteed to be NUL-terminated
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| 48 | * (though the buffer will have trailing NUL padding when the
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| 49 | * file size was smaller than the buffer size).
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| 50 | *
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| 51 | * We do not want to exec a truncated interpreter path, so either
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| 52 | * we find a newline (which indicates nothing is truncated), or
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| 53 | * we find a space/tab/NUL after the interpreter path (which
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| 54 | * itself may be preceded by spaces/tabs). Truncating the
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| 55 | * arguments is fine: the interpreter can re-read the script to
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| 56 | * parse them on its own.
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| 57 |
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| 58 | buf_end = bprm->buf + sizeof(bprm->buf) - 1;
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| 59 | i_end = strnchr(bprm->buf, sizeof(bprm->buf), '\n');
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| 60 | if (!i_end) {
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| 61 | i_end = next_non_spacetab(bprm->buf + 2, buf_end);
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| 62 | if (!i_end)
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| 63 | return -ENOEXEC;
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| 64 | |
| 65 | * If there is no later space/tab/NUL we must assume the
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| 66 | * interpreter path is truncated.
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| 67 |
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| 68 | if (!next_terminator(i_end, buf_end))
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| 69 | return -ENOEXEC;
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| 70 | i_end = buf_end;
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| 71 | }
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| 72 |
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| 73 | while (spacetab(i_end[-1]))
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| 74 | i_end--;
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| 75 |
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| 76 |
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| 77 | i_name = next_non_spacetab(bprm->buf+2, i_end);
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| 78 | if (!i_name || (i_name == i_end))
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| 79 | return -ENOEXEC;
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| 80 |
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| 81 |
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| 82 | i_arg = NULL;
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| 83 | i_sep = next_terminator(i_name, i_end);
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| 84 | if (i_sep && (*i_sep != '\0'))
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| 85 | i_arg = next_non_spacetab(i_sep, i_end);
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| 86 |
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| 87 | |
| 88 | * If the script filename will be inaccessible after exec, typically
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| 89 | * because it is a "/dev/fd/<fd>/.." path against an O_CLOEXEC fd, give
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| 90 | * up now (on the assumption that the interpreter will want to load
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| 91 | * this file).
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| 92 |
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| 93 | if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE)
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| 94 | return -ENOENT;
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| 95 |
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| 96 | |
| 97 | * OK, we've parsed out the interpreter name and
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| 98 | * (optional) argument.
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| 99 | * Splice in (1) the interpreter's name for argv[0]
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| 100 | * (2) (optional) argument to interpreter
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| 101 | * (3) filename of shell script (replace argv[0])
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| 102 | *
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| 103 | * This is done in reverse order, because of how the
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| 104 | * user environment and arguments are stored.
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| 105 |
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| 106 | retval = remove_arg_zero(bprm);
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| 107 | if (retval)
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| 108 | return retval;
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| 109 | retval = copy_string_kernel(bprm->interp, bprm);
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| 110 | if (retval < 0)
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| 111 | return retval;
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| 112 | bprm->argc++;
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| 113 | *((char *)i_end) = '\0';
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| 114 | if (i_arg) {
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| 115 | *((char *)i_sep) = '\0';
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| 116 | retval = copy_string_kernel(i_arg, bprm);
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| 117 | if (retval < 0)
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| 118 | return retval;
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| 119 | bprm->argc++;
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| 120 | }
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| 121 | retval = copy_string_kernel(i_name, bprm);
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| 122 | if (retval)
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| 123 | return retval;
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| 124 | bprm->argc++;
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| 125 | retval = bprm_change_interp(i_name, bprm);
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| 126 | if (retval < 0)
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| 127 | return retval;
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| 128 |
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| 129 | |
| 130 | * OK, now restart the process with the interpreter's dentry.
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| 131 |
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| 132 | file = open_exec(i_name);
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| 133 | if (IS_ERR(file))
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| 134 | return PTR_ERR(file);
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| 135 |
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| 136 | bprm->interpreter = file;
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| 137 | return 0;
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| 138 | }
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| 139 |
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| 140 | static struct linux_binfmt script_format = {
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| 141 | .module = THIS_MODULE,
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| 142 | .load_binary = load_script,
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| 143 | };
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| 144 |
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| 145 | static int __init init_script_binfmt(void)
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| 146 | {
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| 147 | register_binfmt(&script_format);
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| 148 | return 0;
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| 149 | }
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| 150 |
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| 151 | static void __exit exit_script_binfmt(void)
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| 152 | {
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| 153 | unregister_binfmt(&script_format);
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| 154 | }
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| 155 |
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| 156 | core_initcall(init_script_binfmt);
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| 157 | module_exit(exit_script_binfmt);
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| 158 | MODULE_LICENSE("GPL");
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