![Peter Hurley](/assets/img/avatar_default.png)
Line discipline drivers may mistakenly misuse ldisc-related fields
when initializing. For example, a failure to initialize tty->receive_room
in the N_GIGASET_M101 line discipline was recently found and fixed [1].
Now, the N_X25 line discipline has been discovered accessing the previous
line discipline's already-freed private data [2].
Harden the ldisc interface against misuse by initializing revelant
tty fields before instancing the new line discipline.
[1]
commit fd98e9419d
Author: Tilman Schmidt <tilman@imap.cc>
Date: Tue Jul 14 00:37:13 2015 +0200
isdn/gigaset: reset tty->receive_room when attaching ser_gigaset
[2] Report from Sasha Levin <sasha.levin@oracle.com>
[ 634.336761] ==================================================================
[ 634.338226] BUG: KASAN: use-after-free in x25_asy_open_tty+0x13d/0x490 at addr ffff8800a743efd0
[ 634.339558] Read of size 4 by task syzkaller_execu/8981
[ 634.340359] =============================================================================
[ 634.341598] BUG kmalloc-512 (Not tainted): kasan: bad access detected
...
[ 634.405018] Call Trace:
[ 634.405277] dump_stack (lib/dump_stack.c:52)
[ 634.405775] print_trailer (mm/slub.c:655)
[ 634.406361] object_err (mm/slub.c:662)
[ 634.406824] kasan_report_error (mm/kasan/report.c:138 mm/kasan/report.c:236)
[ 634.409581] __asan_report_load4_noabort (mm/kasan/report.c:279)
[ 634.411355] x25_asy_open_tty (drivers/net/wan/x25_asy.c:559 (discriminator 1))
[ 634.413997] tty_ldisc_open.isra.2 (drivers/tty/tty_ldisc.c:447)
[ 634.414549] tty_set_ldisc (drivers/tty/tty_ldisc.c:567)
[ 634.415057] tty_ioctl (drivers/tty/tty_io.c:2646 drivers/tty/tty_io.c:2879)
[ 634.423524] do_vfs_ioctl (fs/ioctl.c:43 fs/ioctl.c:607)
[ 634.427491] SyS_ioctl (fs/ioctl.c:622 fs/ioctl.c:613)
[ 634.427945] entry_SYSCALL_64_fastpath (arch/x86/entry/entry_64.S:188)
Cc: Tilman Schmidt <tilman@imap.cc>
Cc: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
817 lines
19 KiB
C
817 lines
19 KiB
C
#include <linux/types.h>
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#include <linux/errno.h>
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#include <linux/kmod.h>
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#include <linux/sched.h>
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#include <linux/interrupt.h>
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#include <linux/tty.h>
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#include <linux/tty_driver.h>
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#include <linux/file.h>
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#include <linux/mm.h>
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#include <linux/string.h>
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#include <linux/slab.h>
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#include <linux/poll.h>
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#include <linux/proc_fs.h>
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#include <linux/module.h>
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#include <linux/device.h>
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#include <linux/wait.h>
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#include <linux/bitops.h>
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#include <linux/seq_file.h>
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#include <linux/uaccess.h>
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#include <linux/ratelimit.h>
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#undef LDISC_DEBUG_HANGUP
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#ifdef LDISC_DEBUG_HANGUP
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#define tty_ldisc_debug(tty, f, args...) tty_debug(tty, f, ##args)
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#else
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#define tty_ldisc_debug(tty, f, args...)
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#endif
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/* lockdep nested classes for tty->ldisc_sem */
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enum {
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LDISC_SEM_NORMAL,
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LDISC_SEM_OTHER,
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};
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/*
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* This guards the refcounted line discipline lists. The lock
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* must be taken with irqs off because there are hangup path
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* callers who will do ldisc lookups and cannot sleep.
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*/
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static DEFINE_RAW_SPINLOCK(tty_ldiscs_lock);
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/* Line disc dispatch table */
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static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS];
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/**
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* tty_register_ldisc - install a line discipline
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* @disc: ldisc number
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* @new_ldisc: pointer to the ldisc object
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*
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* Installs a new line discipline into the kernel. The discipline
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* is set up as unreferenced and then made available to the kernel
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* from this point onwards.
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*
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* Locking:
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* takes tty_ldiscs_lock to guard against ldisc races
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*/
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int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc)
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{
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unsigned long flags;
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int ret = 0;
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if (disc < N_TTY || disc >= NR_LDISCS)
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return -EINVAL;
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raw_spin_lock_irqsave(&tty_ldiscs_lock, flags);
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tty_ldiscs[disc] = new_ldisc;
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new_ldisc->num = disc;
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new_ldisc->refcount = 0;
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raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags);
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return ret;
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}
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EXPORT_SYMBOL(tty_register_ldisc);
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/**
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* tty_unregister_ldisc - unload a line discipline
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* @disc: ldisc number
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* @new_ldisc: pointer to the ldisc object
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*
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* Remove a line discipline from the kernel providing it is not
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* currently in use.
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*
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* Locking:
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* takes tty_ldiscs_lock to guard against ldisc races
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*/
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int tty_unregister_ldisc(int disc)
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{
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unsigned long flags;
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int ret = 0;
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if (disc < N_TTY || disc >= NR_LDISCS)
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return -EINVAL;
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raw_spin_lock_irqsave(&tty_ldiscs_lock, flags);
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if (tty_ldiscs[disc]->refcount)
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ret = -EBUSY;
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else
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tty_ldiscs[disc] = NULL;
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raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags);
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return ret;
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}
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EXPORT_SYMBOL(tty_unregister_ldisc);
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static struct tty_ldisc_ops *get_ldops(int disc)
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{
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unsigned long flags;
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struct tty_ldisc_ops *ldops, *ret;
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raw_spin_lock_irqsave(&tty_ldiscs_lock, flags);
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ret = ERR_PTR(-EINVAL);
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ldops = tty_ldiscs[disc];
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if (ldops) {
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ret = ERR_PTR(-EAGAIN);
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if (try_module_get(ldops->owner)) {
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ldops->refcount++;
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ret = ldops;
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}
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}
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raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags);
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return ret;
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}
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static void put_ldops(struct tty_ldisc_ops *ldops)
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{
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unsigned long flags;
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raw_spin_lock_irqsave(&tty_ldiscs_lock, flags);
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ldops->refcount--;
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module_put(ldops->owner);
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raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags);
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}
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/**
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* tty_ldisc_get - take a reference to an ldisc
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* @disc: ldisc number
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*
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* Takes a reference to a line discipline. Deals with refcounts and
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* module locking counts. Returns NULL if the discipline is not available.
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* Returns a pointer to the discipline and bumps the ref count if it is
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* available
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*
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* Locking:
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* takes tty_ldiscs_lock to guard against ldisc races
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*/
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static struct tty_ldisc *tty_ldisc_get(struct tty_struct *tty, int disc)
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{
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struct tty_ldisc *ld;
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struct tty_ldisc_ops *ldops;
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if (disc < N_TTY || disc >= NR_LDISCS)
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return ERR_PTR(-EINVAL);
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/*
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* Get the ldisc ops - we may need to request them to be loaded
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* dynamically and try again.
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*/
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ldops = get_ldops(disc);
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if (IS_ERR(ldops)) {
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request_module("tty-ldisc-%d", disc);
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ldops = get_ldops(disc);
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if (IS_ERR(ldops))
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return ERR_CAST(ldops);
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}
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ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL);
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if (ld == NULL) {
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put_ldops(ldops);
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return ERR_PTR(-ENOMEM);
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}
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ld->ops = ldops;
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ld->tty = tty;
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return ld;
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}
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/**
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* tty_ldisc_put - release the ldisc
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*
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* Complement of tty_ldisc_get().
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*/
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static void tty_ldisc_put(struct tty_ldisc *ld)
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{
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if (WARN_ON_ONCE(!ld))
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return;
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put_ldops(ld->ops);
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kfree(ld);
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}
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static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos)
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{
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return (*pos < NR_LDISCS) ? pos : NULL;
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}
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static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos)
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{
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(*pos)++;
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return (*pos < NR_LDISCS) ? pos : NULL;
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}
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static void tty_ldiscs_seq_stop(struct seq_file *m, void *v)
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{
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}
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static int tty_ldiscs_seq_show(struct seq_file *m, void *v)
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{
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int i = *(loff_t *)v;
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struct tty_ldisc_ops *ldops;
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ldops = get_ldops(i);
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if (IS_ERR(ldops))
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return 0;
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seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i);
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put_ldops(ldops);
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return 0;
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}
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static const struct seq_operations tty_ldiscs_seq_ops = {
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.start = tty_ldiscs_seq_start,
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.next = tty_ldiscs_seq_next,
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.stop = tty_ldiscs_seq_stop,
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.show = tty_ldiscs_seq_show,
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};
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static int proc_tty_ldiscs_open(struct inode *inode, struct file *file)
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{
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return seq_open(file, &tty_ldiscs_seq_ops);
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}
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const struct file_operations tty_ldiscs_proc_fops = {
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.owner = THIS_MODULE,
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.open = proc_tty_ldiscs_open,
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.read = seq_read,
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.llseek = seq_lseek,
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.release = seq_release,
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};
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/**
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* tty_ldisc_ref_wait - wait for the tty ldisc
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* @tty: tty device
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*
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* Dereference the line discipline for the terminal and take a
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* reference to it. If the line discipline is in flux then
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* wait patiently until it changes.
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*
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* Note: Must not be called from an IRQ/timer context. The caller
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* must also be careful not to hold other locks that will deadlock
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* against a discipline change, such as an existing ldisc reference
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* (which we check for)
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*
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* Note: only callable from a file_operations routine (which
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* guarantees tty->ldisc != NULL when the lock is acquired).
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*/
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struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty)
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{
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ldsem_down_read(&tty->ldisc_sem, MAX_SCHEDULE_TIMEOUT);
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WARN_ON(!tty->ldisc);
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return tty->ldisc;
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}
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EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait);
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/**
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* tty_ldisc_ref - get the tty ldisc
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* @tty: tty device
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*
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* Dereference the line discipline for the terminal and take a
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* reference to it. If the line discipline is in flux then
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* return NULL. Can be called from IRQ and timer functions.
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*/
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struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty)
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{
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struct tty_ldisc *ld = NULL;
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if (ldsem_down_read_trylock(&tty->ldisc_sem)) {
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ld = tty->ldisc;
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if (!ld)
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ldsem_up_read(&tty->ldisc_sem);
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}
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return ld;
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}
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EXPORT_SYMBOL_GPL(tty_ldisc_ref);
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/**
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* tty_ldisc_deref - free a tty ldisc reference
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* @ld: reference to free up
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*
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* Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May
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* be called in IRQ context.
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*/
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void tty_ldisc_deref(struct tty_ldisc *ld)
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{
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ldsem_up_read(&ld->tty->ldisc_sem);
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}
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EXPORT_SYMBOL_GPL(tty_ldisc_deref);
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static inline int __lockfunc
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__tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout)
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{
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return ldsem_down_write(&tty->ldisc_sem, timeout);
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}
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static inline int __lockfunc
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__tty_ldisc_lock_nested(struct tty_struct *tty, unsigned long timeout)
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{
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return ldsem_down_write_nested(&tty->ldisc_sem,
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LDISC_SEM_OTHER, timeout);
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}
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static inline void __tty_ldisc_unlock(struct tty_struct *tty)
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{
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ldsem_up_write(&tty->ldisc_sem);
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}
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static int __lockfunc
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tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout)
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{
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int ret;
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ret = __tty_ldisc_lock(tty, timeout);
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if (!ret)
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return -EBUSY;
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set_bit(TTY_LDISC_HALTED, &tty->flags);
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return 0;
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}
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static void tty_ldisc_unlock(struct tty_struct *tty)
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{
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clear_bit(TTY_LDISC_HALTED, &tty->flags);
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__tty_ldisc_unlock(tty);
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}
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static int __lockfunc
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tty_ldisc_lock_pair_timeout(struct tty_struct *tty, struct tty_struct *tty2,
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unsigned long timeout)
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{
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int ret;
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if (tty < tty2) {
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ret = __tty_ldisc_lock(tty, timeout);
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if (ret) {
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ret = __tty_ldisc_lock_nested(tty2, timeout);
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if (!ret)
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__tty_ldisc_unlock(tty);
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}
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} else {
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/* if this is possible, it has lots of implications */
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WARN_ON_ONCE(tty == tty2);
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if (tty2 && tty != tty2) {
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ret = __tty_ldisc_lock(tty2, timeout);
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if (ret) {
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ret = __tty_ldisc_lock_nested(tty, timeout);
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if (!ret)
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__tty_ldisc_unlock(tty2);
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}
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} else
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ret = __tty_ldisc_lock(tty, timeout);
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}
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if (!ret)
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return -EBUSY;
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set_bit(TTY_LDISC_HALTED, &tty->flags);
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if (tty2)
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set_bit(TTY_LDISC_HALTED, &tty2->flags);
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return 0;
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}
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static void __lockfunc
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tty_ldisc_lock_pair(struct tty_struct *tty, struct tty_struct *tty2)
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{
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tty_ldisc_lock_pair_timeout(tty, tty2, MAX_SCHEDULE_TIMEOUT);
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}
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static void __lockfunc tty_ldisc_unlock_pair(struct tty_struct *tty,
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struct tty_struct *tty2)
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{
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__tty_ldisc_unlock(tty);
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if (tty2)
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__tty_ldisc_unlock(tty2);
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}
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/**
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* tty_ldisc_flush - flush line discipline queue
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* @tty: tty
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*
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* Flush the line discipline queue (if any) and the tty flip buffers
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* for this tty.
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*/
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void tty_ldisc_flush(struct tty_struct *tty)
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{
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struct tty_ldisc *ld = tty_ldisc_ref(tty);
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tty_buffer_flush(tty, ld);
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if (ld)
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tty_ldisc_deref(ld);
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}
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EXPORT_SYMBOL_GPL(tty_ldisc_flush);
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/**
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* tty_set_termios_ldisc - set ldisc field
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* @tty: tty structure
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* @num: line discipline number
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*
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* This is probably overkill for real world processors but
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* they are not on hot paths so a little discipline won't do
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* any harm.
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*
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* The line discipline-related tty_struct fields are reset to
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* prevent the ldisc driver from re-using stale information for
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* the new ldisc instance.
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*
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* Locking: takes termios_rwsem
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*/
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static void tty_set_termios_ldisc(struct tty_struct *tty, int num)
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{
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down_write(&tty->termios_rwsem);
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tty->termios.c_line = num;
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up_write(&tty->termios_rwsem);
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tty->disc_data = NULL;
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tty->receive_room = 0;
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}
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/**
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* tty_ldisc_open - open a line discipline
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* @tty: tty we are opening the ldisc on
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* @ld: discipline to open
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*
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* A helper opening method. Also a convenient debugging and check
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* point.
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*
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* Locking: always called with BTM already held.
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*/
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static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld)
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{
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WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags));
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if (ld->ops->open) {
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int ret;
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/* BTM here locks versus a hangup event */
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ret = ld->ops->open(tty);
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if (ret)
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clear_bit(TTY_LDISC_OPEN, &tty->flags);
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tty_ldisc_debug(tty, "%p: opened\n", tty->ldisc);
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return ret;
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}
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return 0;
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}
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/**
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* tty_ldisc_close - close a line discipline
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* @tty: tty we are opening the ldisc on
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* @ld: discipline to close
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*
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* A helper close method. Also a convenient debugging and check
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* point.
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*/
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static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld)
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{
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WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags));
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clear_bit(TTY_LDISC_OPEN, &tty->flags);
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if (ld->ops->close)
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ld->ops->close(tty);
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tty_ldisc_debug(tty, "%p: closed\n", tty->ldisc);
|
|
}
|
|
|
|
/**
|
|
* tty_ldisc_restore - helper for tty ldisc change
|
|
* @tty: tty to recover
|
|
* @old: previous ldisc
|
|
*
|
|
* Restore the previous line discipline or N_TTY when a line discipline
|
|
* change fails due to an open error
|
|
*/
|
|
|
|
static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old)
|
|
{
|
|
struct tty_ldisc *new_ldisc;
|
|
int r;
|
|
|
|
/* There is an outstanding reference here so this is safe */
|
|
old = tty_ldisc_get(tty, old->ops->num);
|
|
WARN_ON(IS_ERR(old));
|
|
tty->ldisc = old;
|
|
tty_set_termios_ldisc(tty, old->ops->num);
|
|
if (tty_ldisc_open(tty, old) < 0) {
|
|
tty_ldisc_put(old);
|
|
/* This driver is always present */
|
|
new_ldisc = tty_ldisc_get(tty, N_TTY);
|
|
if (IS_ERR(new_ldisc))
|
|
panic("n_tty: get");
|
|
tty->ldisc = new_ldisc;
|
|
tty_set_termios_ldisc(tty, N_TTY);
|
|
r = tty_ldisc_open(tty, new_ldisc);
|
|
if (r < 0)
|
|
panic("Couldn't open N_TTY ldisc for "
|
|
"%s --- error %d.",
|
|
tty_name(tty), r);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* tty_set_ldisc - set line discipline
|
|
* @tty: the terminal to set
|
|
* @ldisc: the line discipline
|
|
*
|
|
* Set the discipline of a tty line. Must be called from a process
|
|
* context. The ldisc change logic has to protect itself against any
|
|
* overlapping ldisc change (including on the other end of pty pairs),
|
|
* the close of one side of a tty/pty pair, and eventually hangup.
|
|
*/
|
|
|
|
int tty_set_ldisc(struct tty_struct *tty, int ldisc)
|
|
{
|
|
int retval;
|
|
struct tty_ldisc *old_ldisc, *new_ldisc;
|
|
|
|
new_ldisc = tty_ldisc_get(tty, ldisc);
|
|
if (IS_ERR(new_ldisc))
|
|
return PTR_ERR(new_ldisc);
|
|
|
|
tty_lock(tty);
|
|
retval = tty_ldisc_lock(tty, 5 * HZ);
|
|
if (retval)
|
|
goto err;
|
|
|
|
/* Check the no-op case */
|
|
if (tty->ldisc->ops->num == ldisc)
|
|
goto out;
|
|
|
|
if (test_bit(TTY_HUPPED, &tty->flags)) {
|
|
/* We were raced by hangup */
|
|
retval = -EIO;
|
|
goto out;
|
|
}
|
|
|
|
old_ldisc = tty->ldisc;
|
|
|
|
/* Shutdown the old discipline. */
|
|
tty_ldisc_close(tty, old_ldisc);
|
|
|
|
/* Now set up the new line discipline. */
|
|
tty->ldisc = new_ldisc;
|
|
tty_set_termios_ldisc(tty, ldisc);
|
|
|
|
retval = tty_ldisc_open(tty, new_ldisc);
|
|
if (retval < 0) {
|
|
/* Back to the old one or N_TTY if we can't */
|
|
tty_ldisc_put(new_ldisc);
|
|
tty_ldisc_restore(tty, old_ldisc);
|
|
}
|
|
|
|
if (tty->ldisc->ops->num != old_ldisc->ops->num && tty->ops->set_ldisc) {
|
|
down_read(&tty->termios_rwsem);
|
|
tty->ops->set_ldisc(tty);
|
|
up_read(&tty->termios_rwsem);
|
|
}
|
|
|
|
/* At this point we hold a reference to the new ldisc and a
|
|
reference to the old ldisc, or we hold two references to
|
|
the old ldisc (if it was restored as part of error cleanup
|
|
above). In either case, releasing a single reference from
|
|
the old ldisc is correct. */
|
|
new_ldisc = old_ldisc;
|
|
out:
|
|
tty_ldisc_unlock(tty);
|
|
|
|
/* Restart the work queue in case no characters kick it off. Safe if
|
|
already running */
|
|
tty_buffer_restart_work(tty->port);
|
|
err:
|
|
tty_ldisc_put(new_ldisc); /* drop the extra reference */
|
|
tty_unlock(tty);
|
|
return retval;
|
|
}
|
|
|
|
/**
|
|
* tty_reset_termios - reset terminal state
|
|
* @tty: tty to reset
|
|
*
|
|
* Restore a terminal to the driver default state.
|
|
*/
|
|
|
|
static void tty_reset_termios(struct tty_struct *tty)
|
|
{
|
|
down_write(&tty->termios_rwsem);
|
|
tty->termios = tty->driver->init_termios;
|
|
tty->termios.c_ispeed = tty_termios_input_baud_rate(&tty->termios);
|
|
tty->termios.c_ospeed = tty_termios_baud_rate(&tty->termios);
|
|
up_write(&tty->termios_rwsem);
|
|
}
|
|
|
|
|
|
/**
|
|
* tty_ldisc_reinit - reinitialise the tty ldisc
|
|
* @tty: tty to reinit
|
|
* @ldisc: line discipline to reinitialize
|
|
*
|
|
* Switch the tty to a line discipline and leave the ldisc
|
|
* state closed
|
|
*/
|
|
|
|
static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc)
|
|
{
|
|
struct tty_ldisc *ld = tty_ldisc_get(tty, ldisc);
|
|
|
|
if (IS_ERR(ld))
|
|
return -1;
|
|
|
|
tty_ldisc_close(tty, tty->ldisc);
|
|
tty_ldisc_put(tty->ldisc);
|
|
/*
|
|
* Switch the line discipline back
|
|
*/
|
|
tty->ldisc = ld;
|
|
tty_set_termios_ldisc(tty, ldisc);
|
|
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* tty_ldisc_hangup - hangup ldisc reset
|
|
* @tty: tty being hung up
|
|
*
|
|
* Some tty devices reset their termios when they receive a hangup
|
|
* event. In that situation we must also switch back to N_TTY properly
|
|
* before we reset the termios data.
|
|
*
|
|
* Locking: We can take the ldisc mutex as the rest of the code is
|
|
* careful to allow for this.
|
|
*
|
|
* In the pty pair case this occurs in the close() path of the
|
|
* tty itself so we must be careful about locking rules.
|
|
*/
|
|
|
|
void tty_ldisc_hangup(struct tty_struct *tty)
|
|
{
|
|
struct tty_ldisc *ld;
|
|
int reset = tty->driver->flags & TTY_DRIVER_RESET_TERMIOS;
|
|
int err = 0;
|
|
|
|
tty_ldisc_debug(tty, "%p: closing\n", tty->ldisc);
|
|
|
|
ld = tty_ldisc_ref(tty);
|
|
if (ld != NULL) {
|
|
if (ld->ops->flush_buffer)
|
|
ld->ops->flush_buffer(tty);
|
|
tty_driver_flush_buffer(tty);
|
|
if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) &&
|
|
ld->ops->write_wakeup)
|
|
ld->ops->write_wakeup(tty);
|
|
if (ld->ops->hangup)
|
|
ld->ops->hangup(tty);
|
|
tty_ldisc_deref(ld);
|
|
}
|
|
|
|
wake_up_interruptible_poll(&tty->write_wait, POLLOUT);
|
|
wake_up_interruptible_poll(&tty->read_wait, POLLIN);
|
|
|
|
/*
|
|
* Shutdown the current line discipline, and reset it to
|
|
* N_TTY if need be.
|
|
*
|
|
* Avoid racing set_ldisc or tty_ldisc_release
|
|
*/
|
|
tty_ldisc_lock(tty, MAX_SCHEDULE_TIMEOUT);
|
|
|
|
if (tty->ldisc) {
|
|
|
|
/* At this point we have a halted ldisc; we want to close it and
|
|
reopen a new ldisc. We could defer the reopen to the next
|
|
open but it means auditing a lot of other paths so this is
|
|
a FIXME */
|
|
if (reset == 0) {
|
|
|
|
if (!tty_ldisc_reinit(tty, tty->termios.c_line))
|
|
err = tty_ldisc_open(tty, tty->ldisc);
|
|
else
|
|
err = 1;
|
|
}
|
|
/* If the re-open fails or we reset then go to N_TTY. The
|
|
N_TTY open cannot fail */
|
|
if (reset || err) {
|
|
BUG_ON(tty_ldisc_reinit(tty, N_TTY));
|
|
WARN_ON(tty_ldisc_open(tty, tty->ldisc));
|
|
}
|
|
}
|
|
tty_ldisc_unlock(tty);
|
|
if (reset)
|
|
tty_reset_termios(tty);
|
|
|
|
tty_ldisc_debug(tty, "%p: re-opened\n", tty->ldisc);
|
|
}
|
|
|
|
/**
|
|
* tty_ldisc_setup - open line discipline
|
|
* @tty: tty being shut down
|
|
* @o_tty: pair tty for pty/tty pairs
|
|
*
|
|
* Called during the initial open of a tty/pty pair in order to set up the
|
|
* line disciplines and bind them to the tty. This has no locking issues
|
|
* as the device isn't yet active.
|
|
*/
|
|
|
|
int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty)
|
|
{
|
|
struct tty_ldisc *ld = tty->ldisc;
|
|
int retval;
|
|
|
|
retval = tty_ldisc_open(tty, ld);
|
|
if (retval)
|
|
return retval;
|
|
|
|
if (o_tty) {
|
|
retval = tty_ldisc_open(o_tty, o_tty->ldisc);
|
|
if (retval) {
|
|
tty_ldisc_close(tty, ld);
|
|
return retval;
|
|
}
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static void tty_ldisc_kill(struct tty_struct *tty)
|
|
{
|
|
/*
|
|
* Now kill off the ldisc
|
|
*/
|
|
tty_ldisc_close(tty, tty->ldisc);
|
|
tty_ldisc_put(tty->ldisc);
|
|
/* Force an oops if we mess this up */
|
|
tty->ldisc = NULL;
|
|
|
|
/* Ensure the next open requests the N_TTY ldisc */
|
|
tty_set_termios_ldisc(tty, N_TTY);
|
|
}
|
|
|
|
/**
|
|
* tty_ldisc_release - release line discipline
|
|
* @tty: tty being shut down (or one end of pty pair)
|
|
*
|
|
* Called during the final close of a tty or a pty pair in order to shut
|
|
* down the line discpline layer. On exit, each ldisc assigned is N_TTY and
|
|
* each ldisc has not been opened.
|
|
*/
|
|
|
|
void tty_ldisc_release(struct tty_struct *tty)
|
|
{
|
|
struct tty_struct *o_tty = tty->link;
|
|
|
|
/*
|
|
* Shutdown this line discipline. As this is the final close,
|
|
* it does not race with the set_ldisc code path.
|
|
*/
|
|
|
|
tty_ldisc_lock_pair(tty, o_tty);
|
|
tty_ldisc_kill(tty);
|
|
if (o_tty)
|
|
tty_ldisc_kill(o_tty);
|
|
tty_ldisc_unlock_pair(tty, o_tty);
|
|
|
|
/* And the memory resources remaining (buffers, termios) will be
|
|
disposed of when the kref hits zero */
|
|
|
|
tty_ldisc_debug(tty, "released\n");
|
|
}
|
|
|
|
/**
|
|
* tty_ldisc_init - ldisc setup for new tty
|
|
* @tty: tty being allocated
|
|
*
|
|
* Set up the line discipline objects for a newly allocated tty. Note that
|
|
* the tty structure is not completely set up when this call is made.
|
|
*/
|
|
|
|
void tty_ldisc_init(struct tty_struct *tty)
|
|
{
|
|
struct tty_ldisc *ld = tty_ldisc_get(tty, N_TTY);
|
|
if (IS_ERR(ld))
|
|
panic("n_tty: init_tty");
|
|
tty->ldisc = ld;
|
|
}
|
|
|
|
/**
|
|
* tty_ldisc_init - ldisc cleanup for new tty
|
|
* @tty: tty that was allocated recently
|
|
*
|
|
* The tty structure must not becompletely set up (tty_ldisc_setup) when
|
|
* this call is made.
|
|
*/
|
|
void tty_ldisc_deinit(struct tty_struct *tty)
|
|
{
|
|
tty_ldisc_put(tty->ldisc);
|
|
tty->ldisc = NULL;
|
|
}
|
|
|
|
void tty_ldisc_begin(void)
|
|
{
|
|
/* Setup the default TTY line discipline. */
|
|
(void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY);
|
|
}
|