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