fs/binfmt_script.c

   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
  17 static int load_script(struct linux_binprm *bprm)
  18 {
  19         const char *i_arg, *i_name;
  20         char *cp;
  21         struct file *file;
  22         int retval;
  23
  24         if ((bprm->buf[0] != '#') || (bprm->buf[1] != '!'))
  25                 return -ENOEXEC;
  26
  27         /*
  28          * If the script filename will be inaccessible after exec, typically
  29          * because it is a "/dev/fd/<fd>/.." path against an O_CLOEXEC fd, give
  30          * up now (on the assumption that the interpreter will want to load
  31          * this file).
  32          */
  33         if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE)
  34                 return -ENOENT;
  35
  36         /*
  37          * This section does the #! interpretation.
  38          * Sorta complicated, but hopefully it will work.  -TYT
  39          */
  40
  41         allow_write_access(bprm->file);
  42         fput(bprm->file);
  43         bprm->file = NULL;
  44
  45         for (cp = bprm->buf+2;; cp++) {
  46                 if (cp >= bprm->buf + BINPRM_BUF_SIZE)
  47                         return -ENOEXEC;
  48                 if (!*cp || (*cp == '\n'))
  49                         break;
  50         }
  51         *cp = '\0';
  52
  53         while (cp > bprm->buf) {
  54                 cp--;
  55                 if ((*cp == ' ') || (*cp == '\t'))
  56                         *cp = '\0';
  57                 else
  58                         break;
  59         }
  60         for (cp = bprm->buf+2; (*cp == ' ') || (*cp == '\t'); cp++);
  61         if (*cp == '\0')
  62                 return -ENOEXEC; /* No interpreter name found */
  63         i_name = cp;
  64         i_arg = NULL;
  65         for ( ; *cp && (*cp != ' ') && (*cp != '\t'); cp++)
  66                 /* nothing */ ;
  67         while ((*cp == ' ') || (*cp == '\t'))
  68                 *cp++ = '\0';
  69         if (*cp)
  70                 i_arg = cp;
  71         /*
  72          * OK, we've parsed out the interpreter name and
  73          * (optional) argument.
  74          * Splice in (1) the interpreter's name for argv[0]
  75          *           (2) (optional) argument to interpreter
  76          *           (3) filename of shell script (replace argv[0])
  77          *
  78          * This is done in reverse order, because of how the
  79          * user environment and arguments are stored.
  80          */
  81         retval = remove_arg_zero(bprm);
  82         if (retval)
  83                 return retval;
  84         retval = copy_strings_kernel(1, &bprm->interp, bprm);
  85         if (retval < 0)
  86                 return retval;
  87         bprm->argc++;
  88         if (i_arg) {
  89                 retval = copy_strings_kernel(1, &i_arg, bprm);
  90                 if (retval < 0)
  91                         return retval;
  92                 bprm->argc++;
  93         }
  94         retval = copy_strings_kernel(1, &i_name, bprm);
  95         if (retval)
  96                 return retval;
  97         bprm->argc++;
  98         retval = bprm_change_interp(i_name, bprm);
  99         if (retval < 0)
 100                 return retval;
 101
 102         /*
 103          * OK, now restart the process with the interpreter's dentry.
 104          */
 105         file = open_exec(i_name);
 106         if (IS_ERR(file))
 107                 return PTR_ERR(file);
 108
 109         bprm->file = file;
 110         retval = prepare_binprm(bprm);
 111         if (retval < 0)
 112                 return retval;
 113         return search_binary_handler(bprm);
 114 }
 115
 116 static struct linux_binfmt script_format = {
 117         .module         = THIS_MODULE,
 118         .load_binary    = load_script,
 119 };
 120
 121 static int __init init_script_binfmt(void)
 122 {
 123         register_binfmt(&script_format);
 124         return 0;
 125 }
 126
 127 static void __exit exit_script_binfmt(void)
 128 {
 129         unregister_binfmt(&script_format);
 130 }
 131
 132 core_initcall(init_script_binfmt);
 133 module_exit(exit_script_binfmt);
 134 MODULE_LICENSE("GPL");