linux/fs/binfmt_script.c
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   1/*
   2 *  linux/fs/binfmt_script.c
   3 *
   4 *  Copyright (C) 1996  Martin von L\xC3\xB6wis
   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
  17static 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
 111static struct linux_binfmt script_format = {
 112        .module         = THIS_MODULE,
 113        .load_binary    = load_script,
 114};
 115
 116static int __init init_script_binfmt(void)
 117{
 118        register_binfmt(&script_format);
 119        return 0;
 120}
 121
 122static void __exit exit_script_binfmt(void)
 123{
 124        unregister_binfmt(&script_format);
 125}
 126
 127core_initcall(init_script_binfmt);
 128module_exit(exit_script_binfmt);
 129MODULE_LICENSE("GPL");
 130
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