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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * linux/fs/binfmt_script.c4 *5 * Copyright (C) 1996 Martin von Löwis6 * original #!-checking implemented by tytso.7 */8 9#include <linux/module.h>10#include <linux/string.h>11#include <linux/stat.h>12#include <linux/binfmts.h>13#include <linux/init.h>14#include <linux/file.h>15#include <linux/err.h>16#include <linux/fs.h>17 18static inline bool spacetab(char c) { return c == ' ' || c == '\t'; }19static inline const char *next_non_spacetab(const char *first, const char *last)20{21 for (; first <= last; first++)22 if (!spacetab(*first))23 return first;24 return NULL;25}26static inline const char *next_terminator(const char *first, const char *last)27{28 for (; first <= last; first++)29 if (spacetab(*first) || !*first)30 return first;31 return NULL;32}33 34static int load_script(struct linux_binprm *bprm)35{36 const char *i_name, *i_sep, *i_arg, *i_end, *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 * This section handles parsing the #! line into separate46 * interpreter path and argument strings. We must be careful47 * because bprm->buf is not yet guaranteed to be NUL-terminated48 * (though the buffer will have trailing NUL padding when the49 * file size was smaller than the buffer size).50 *51 * We do not want to exec a truncated interpreter path, so either52 * we find a newline (which indicates nothing is truncated), or53 * we find a space/tab/NUL after the interpreter path (which54 * itself may be preceded by spaces/tabs). Truncating the55 * arguments is fine: the interpreter can re-read the script to56 * parse them on its own.57 */58 buf_end = bprm->buf + sizeof(bprm->buf) - 1;59 i_end = strnchr(bprm->buf, sizeof(bprm->buf), '\n');60 if (!i_end) {61 i_end = next_non_spacetab(bprm->buf + 2, buf_end);62 if (!i_end)63 return -ENOEXEC; /* Entire buf is spaces/tabs */64 /*65 * If there is no later space/tab/NUL we must assume the66 * interpreter path is truncated.67 */68 if (!next_terminator(i_end, buf_end))69 return -ENOEXEC;70 i_end = buf_end;71 }72 /* Trim any trailing spaces/tabs from i_end */73 while (spacetab(i_end[-1]))74 i_end--;75 76 /* Skip over leading spaces/tabs */77 i_name = next_non_spacetab(bprm->buf+2, i_end);78 if (!i_name || (i_name == i_end))79 return -ENOEXEC; /* No interpreter name found */80 81 /* Is there an optional argument? */82 i_arg = NULL;83 i_sep = next_terminator(i_name, i_end);84 if (i_sep && (*i_sep != '\0'))85 i_arg = next_non_spacetab(i_sep, i_end);86 87 /*88 * If the script filename will be inaccessible after exec, typically89 * because it is a "/dev/fd/<fd>/.." path against an O_CLOEXEC fd, give90 * up now (on the assumption that the interpreter will want to load91 * this file).92 */93 if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE)94 return -ENOENT;95 96 /*97 * OK, we've parsed out the interpreter name and98 * (optional) argument.99 * Splice in (1) the interpreter's name for argv[0]100 * (2) (optional) argument to interpreter101 * (3) filename of shell script (replace argv[0])102 *103 * This is done in reverse order, because of how the104 * user environment and arguments are stored.105 */106 retval = remove_arg_zero(bprm);107 if (retval)108 return retval;109 retval = copy_string_kernel(bprm->interp, bprm);110 if (retval < 0)111 return retval;112 bprm->argc++;113 *((char *)i_end) = '\0';114 if (i_arg) {115 *((char *)i_sep) = '\0';116 retval = copy_string_kernel(i_arg, bprm);117 if (retval < 0)118 return retval;119 bprm->argc++;120 }121 retval = copy_string_kernel(i_name, bprm);122 if (retval)123 return retval;124 bprm->argc++;125 retval = bprm_change_interp(i_name, bprm);126 if (retval < 0)127 return retval;128 129 /*130 * OK, now restart the process with the interpreter's dentry.131 */132 file = open_exec(i_name);133 if (IS_ERR(file))134 return PTR_ERR(file);135 136 bprm->interpreter = file;137 return 0;138}139 140static struct linux_binfmt script_format = {141 .module = THIS_MODULE,142 .load_binary = load_script,143};144 145static int __init init_script_binfmt(void)146{147 register_binfmt(&script_format);148 return 0;149}150 151static void __exit exit_script_binfmt(void)152{153 unregister_binfmt(&script_format);154}155 156core_initcall(init_script_binfmt);157module_exit(exit_script_binfmt);158MODULE_DESCRIPTION("Kernel support for scripts starting with #!");159MODULE_LICENSE("GPL");160