mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-13 00:26:41 +07:00
8a8dabf2dd
Historically the N_TTY driver could never fail but this has become broken over time. Rather than trying to rewrite half the ldisc layer to fix the breakage introduce a second level of fallback with an N_NULL ldisc which cannot fail, and thus restore the guarantees required by the ldisc layer. We still try and fail to N_TTY first. It's much more useful to find yourself back in your old ldisc (first attempt) or in N_TTY (second attempt), and while I'm not aware of any code out there that makes those assumptions it's good to drive(r) defensively. Signed-off-by: Alan Cox <alan@linux.intel.com> Reported-by: Dmitry Vyukov <dvyukov@google.com> Tested-by: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
81 lines
1.9 KiB
C
81 lines
1.9 KiB
C
#include <linux/types.h>
|
|
#include <linux/errno.h>
|
|
#include <linux/tty.h>
|
|
#include <linux/module.h>
|
|
|
|
/*
|
|
* n_null.c - Null line discipline used in the failure path
|
|
*
|
|
* Copyright (C) Intel 2017
|
|
*
|
|
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License version 2
|
|
* as published by the Free Software Foundation.
|
|
*
|
|
* This program is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
* GNU General Public License for more details.
|
|
*
|
|
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
*/
|
|
|
|
static int n_null_open(struct tty_struct *tty)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
static void n_null_close(struct tty_struct *tty)
|
|
{
|
|
}
|
|
|
|
static ssize_t n_null_read(struct tty_struct *tty, struct file *file,
|
|
unsigned char __user * buf, size_t nr)
|
|
{
|
|
return -EOPNOTSUPP;
|
|
}
|
|
|
|
static ssize_t n_null_write(struct tty_struct *tty, struct file *file,
|
|
const unsigned char *buf, size_t nr)
|
|
{
|
|
return -EOPNOTSUPP;
|
|
}
|
|
|
|
static void n_null_receivebuf(struct tty_struct *tty,
|
|
const unsigned char *cp, char *fp,
|
|
int cnt)
|
|
{
|
|
}
|
|
|
|
static struct tty_ldisc_ops null_ldisc = {
|
|
.owner = THIS_MODULE,
|
|
.magic = TTY_LDISC_MAGIC,
|
|
.name = "n_null",
|
|
.open = n_null_open,
|
|
.close = n_null_close,
|
|
.read = n_null_read,
|
|
.write = n_null_write,
|
|
.receive_buf = n_null_receivebuf
|
|
};
|
|
|
|
static int __init n_null_init(void)
|
|
{
|
|
BUG_ON(tty_register_ldisc(N_NULL, &null_ldisc));
|
|
return 0;
|
|
}
|
|
|
|
static void __exit n_null_exit(void)
|
|
{
|
|
tty_unregister_ldisc(N_NULL);
|
|
}
|
|
|
|
module_init(n_null_init);
|
|
module_exit(n_null_exit);
|
|
|
|
MODULE_LICENSE("GPL");
|
|
MODULE_AUTHOR("Alan Cox");
|
|
MODULE_ALIAS_LDISC(N_NULL);
|
|
MODULE_DESCRIPTION("Null ldisc driver");
|