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// SPDX-License-Identifier: GPL-2.0-only
/*
* linux/fs/binfmt_script.c
*
* Copyright (C) 1996 Martin von Löwis
* original #!-checking implemented by tytso.
*/
#include <linux/module.h>
#include <linux/string.h>
#include <linux/stat.h>
#include <linux/binfmts.h>
#include <linux/init.h>
#include <linux/file.h>
#include <linux/err.h>
#include <linux/fs.h>
static inline bool spacetab(char c) { return c == ' ' || c == '\t'; }
static inline const char *next_non_spacetab(const char *first, const char *last)
{
for (; first <= last; first++)
if (!spacetab(*first))
return first;
return NULL;
}
static inline const char *next_terminator(const char *first, const char *last)
{
for (; first <= last; first++)
if (spacetab(*first) || !*first)
return first;
return NULL;
}
static int load_script(struct linux_binprm *bprm)
{
const char *i_name, *i_sep, *i_arg, *i_end, *buf_end;
struct file *file;
int retval;
/* Not ours to exec if we don't start with "#!". */
if ((bprm->buf[0] != '#') || (bprm->buf[1] != '!'))
return -ENOEXEC;
/*
* This section handles parsing the #! line into separate
* interpreter path and argument strings. We must be careful
* because bprm->buf is not yet guaranteed to be NUL-terminated
* (though the buffer will have trailing NUL padding when the
* file size was smaller than the buffer size).
*
* We do not want to exec a truncated interpreter path, so either
* we find a newline (which indicates nothing is truncated), or
* we find a space/tab/NUL after the interpreter path (which
* itself may be preceded by spaces/tabs). Truncating the
* arguments is fine: the interpreter can re-read the script to
* parse them on its own.
*/
buf_end = bprm->buf + sizeof(bprm->buf) - 1;
i_end = strnchr(bprm->buf, sizeof(bprm->buf), '\n');
if (!i_end) {
i_end = next_non_spacetab(bprm->buf + 2, buf_end);
if (!i_end)
return -ENOEXEC; /* Entire buf is spaces/tabs */
/*
* If there is no later space/tab/NUL we must assume the
* interpreter path is truncated.
*/
if (!next_terminator(i_end, buf_end))
return -ENOEXEC;
i_end = buf_end;
}
/* Trim any trailing spaces/tabs from i_end */
while (spacetab(i_end[-1]))
i_end--;
/* Skip over leading spaces/tabs */
i_name = next_non_spacetab(bprm->buf+2, i_end);
if (!i_name || (i_name == i_end))
return -ENOEXEC; /* No interpreter name found */
/* Is there an optional argument? */
i_arg = NULL;
i_sep = next_terminator(i_name, i_end);
if (i_sep && (*i_sep != '\0'))
i_arg = next_non_spacetab(i_sep, i_end);
/*
* If the script filename will be inaccessible after exec, typically
* because it is a "/dev/fd/<fd>/.." path against an O_CLOEXEC fd, give
* up now (on the assumption that the interpreter will want to load
* this file).
*/
if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE)
return -ENOENT;
/*
* OK, we've parsed out the interpreter name and
* (optional) argument.
* Splice in (1) the interpreter's name for argv[0]
* (2) (optional) argument to interpreter
* (3) filename of shell script (replace argv[0])
*
* This is done in reverse order, because of how the
* user environment and arguments are stored.
*/
retval = remove_arg_zero(bprm);
if (retval)
return retval;
retval = copy_string_kernel(bprm->interp, bprm);
if (retval < 0)
return retval;
bprm->argc++;
*((char *)i_end) = '\0';
if (i_arg) {
*((char *)i_sep) = '\0';
retval = copy_string_kernel(i_arg, bprm);
if (retval < 0)
return retval;
bprm->argc++;
}
retval = copy_string_kernel(i_name, bprm);
if (retval)
return retval;
bprm->argc++;
retval = bprm_change_interp(i_name, bprm);
if (retval < 0)
return retval;
/*
* OK, now restart the process with the interpreter's dentry.
*/
file = open_exec(i_name);
if (IS_ERR(file))
return PTR_ERR(file);
bprm->interpreter = file;
return 0;
}
static struct linux_binfmt script_format = {
.module = THIS_MODULE,
.load_binary = load_script,
};
static int __init init_script_binfmt(void)
{
register_binfmt(&script_format);
return 0;
}
static void __exit exit_script_binfmt(void)
{
unregister_binfmt(&script_format);
}
core_initcall(init_script_binfmt);
module_exit(exit_script_binfmt);
MODULE_DESCRIPTION("Kernel support for scripts starting with #!");
MODULE_LICENSE("GPL");
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