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         bprm->buf[BINPRM_BUF_SIZE - 1] = '\0';
  46         if ((cp = strchr(bprm->buf, '\n')) == NULL)
  47                 cp = bprm->buf+BINPRM_BUF_SIZE-1;
  48         *cp = '\0';
  49         while (cp > bprm->buf) {
  50                 cp--;
  51                 if ((*cp == ' ') || (*cp == '\t'))
  52                         *cp = '\0';
  53                 else
  54                         break;
  55         }
  56         for (cp = bprm->buf+2; (*cp == ' ') || (*cp == '\t'); cp++);
  57         if (*cp == '\0')
  58                 return -ENOEXEC; /* No interpreter name found */
  59         i_name = cp;
  60         i_arg = NULL;
  61         for ( ; *cp && (*cp != ' ') && (*cp != '\t'); cp++)
  62                 /* nothing */ ;
  63         while ((*cp == ' ') || (*cp == '\t'))
  64                 *cp++ = '\0';
  65         if (*cp)
  66                 i_arg = cp;
  67         /*
  68          * OK, we've parsed out the interpreter name and
  69          * (optional) argument.
  70          * Splice in (1) the interpreter's name for argv[0]
  71          *           (2) (optional) argument to interpreter
  72          *           (3) filename of shell script (replace argv[0])
  73          *
  74          * This is done in reverse order, because of how the
  75          * user environment and arguments are stored.
  76          */
  77         retval = remove_arg_zero(bprm);
  78         if (retval)
  79                 return retval;
  80         retval = copy_strings_kernel(1, &bprm->interp, bprm);
  81         if (retval < 0)
  82                 return retval;
  83         bprm->argc++;
  84         if (i_arg) {
  85                 retval = copy_strings_kernel(1, &i_arg, bprm);
  86                 if (retval < 0)
  87                         return retval;
  88                 bprm->argc++;
  89         }
  90         retval = copy_strings_kernel(1, &i_name, bprm);
  91         if (retval)
  92                 return retval;
  93         bprm->argc++;
  94         retval = bprm_change_interp(i_name, bprm);
  95         if (retval < 0)
  96                 return retval;
  97
  98         /*
  99          * OK, now restart the process with the interpreter's dentry.
 100          */
 101         file = open_exec(i_name);
 102         if (IS_ERR(file))
 103                 return PTR_ERR(file);
 104
 105         bprm->file = file;
 106         retval = prepare_binprm(bprm);
 107         if (retval < 0)
 108                 return retval;
 109         return search_binary_handler(bprm);
 110 }
 111
 112 static struct linux_binfmt script_format = {
 113         .module         = THIS_MODULE,
 114         .load_binary    = load_script,
 115 };
 116
 117 static int __init init_script_binfmt(void)
 118 {
 119         register_binfmt(&script_format);
 120         return 0;
 121 }
 122
 123 static void __exit exit_script_binfmt(void)
 124 {
 125         unregister_binfmt(&script_format);
 126 }
 127
 128 core_initcall(init_script_binfmt);
 129 module_exit(exit_script_binfmt);
 130 MODULE_LICENSE("GPL");