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094fb49a2d
If userspace races tcsetattr() with a write, the drained condition
might not be guaranteed by the kernel. There is a race window after
checking Tx is empty before tty_set_termios() takes termios_rwsem for
write. During that race window, more characters can be queued by a
racing writer.
Any ongoing transmission might produce garbage during HW's
->set_termios() call. The intent of TCSADRAIN/FLUSH seems to be
preventing such a character corruption. If those flags are set, take
tty's write lock to stop any writer before performing the lower layer
Tx empty check and wait for the pending characters to be sent (if any).
The initial wait for all-writers-done must be placed outside of tty's
write lock to avoid deadlock which makes it impossible to use
tty_wait_until_sent(). The write lock is retried if a racing write is
detected.
Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20230317113318.31327-2-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
120 lines
4.3 KiB
C
120 lines
4.3 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* TTY core internal functions
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*/
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#ifndef _TTY_INTERNAL_H
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#define _TTY_INTERNAL_H
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#define tty_msg(fn, tty, f, ...) \
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fn("%s %s: " f, tty_driver_name(tty), tty_name(tty), ##__VA_ARGS__)
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#define tty_debug(tty, f, ...) tty_msg(pr_debug, tty, f, ##__VA_ARGS__)
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#define tty_notice(tty, f, ...) tty_msg(pr_notice, tty, f, ##__VA_ARGS__)
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#define tty_warn(tty, f, ...) tty_msg(pr_warn, tty, f, ##__VA_ARGS__)
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#define tty_err(tty, f, ...) tty_msg(pr_err, tty, f, ##__VA_ARGS__)
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#define tty_info_ratelimited(tty, f, ...) \
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tty_msg(pr_info_ratelimited, tty, f, ##__VA_ARGS__)
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/*
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* Lock subclasses for tty locks
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*
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* TTY_LOCK_NORMAL is for normal ttys and master ptys.
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* TTY_LOCK_SLAVE is for slave ptys only.
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*
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* Lock subclasses are necessary for handling nested locking with pty pairs.
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* tty locks which use nested locking:
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*
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* legacy_mutex - Nested tty locks are necessary for releasing pty pairs.
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* The stable lock order is master pty first, then slave pty.
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* termios_rwsem - The stable lock order is tty_buffer lock->termios_rwsem.
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* Subclassing this lock enables the slave pty to hold its
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* termios_rwsem when claiming the master tty_buffer lock.
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* tty_buffer lock - slave ptys can claim nested buffer lock when handling
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* signal chars. The stable lock order is slave pty, then
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* master.
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*/
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enum {
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TTY_LOCK_NORMAL = 0,
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TTY_LOCK_SLAVE,
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};
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/* Values for tty->flow_change */
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#define TTY_THROTTLE_SAFE 1
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#define TTY_UNTHROTTLE_SAFE 2
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static inline void __tty_set_flow_change(struct tty_struct *tty, int val)
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{
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tty->flow_change = val;
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}
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static inline void tty_set_flow_change(struct tty_struct *tty, int val)
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{
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tty->flow_change = val;
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smp_mb();
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}
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int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout);
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void tty_ldisc_unlock(struct tty_struct *tty);
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int __tty_check_change(struct tty_struct *tty, int sig);
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int tty_check_change(struct tty_struct *tty);
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void __stop_tty(struct tty_struct *tty);
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void __start_tty(struct tty_struct *tty);
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void tty_write_unlock(struct tty_struct *tty);
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int tty_write_lock(struct tty_struct *tty, int ndelay);
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void tty_vhangup_session(struct tty_struct *tty);
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void tty_open_proc_set_tty(struct file *filp, struct tty_struct *tty);
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int tty_signal_session_leader(struct tty_struct *tty, int exit_session);
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void session_clear_tty(struct pid *session);
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void tty_buffer_free_all(struct tty_port *port);
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void tty_buffer_flush(struct tty_struct *tty, struct tty_ldisc *ld);
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void tty_buffer_init(struct tty_port *port);
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void tty_buffer_set_lock_subclass(struct tty_port *port);
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bool tty_buffer_restart_work(struct tty_port *port);
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bool tty_buffer_cancel_work(struct tty_port *port);
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void tty_buffer_flush_work(struct tty_port *port);
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speed_t tty_termios_input_baud_rate(const struct ktermios *termios);
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void tty_ldisc_hangup(struct tty_struct *tty, bool reset);
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int tty_ldisc_reinit(struct tty_struct *tty, int disc);
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long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
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long tty_jobctrl_ioctl(struct tty_struct *tty, struct tty_struct *real_tty,
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struct file *file, unsigned int cmd, unsigned long arg);
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void tty_default_fops(struct file_operations *fops);
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struct tty_struct *alloc_tty_struct(struct tty_driver *driver, int idx);
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int tty_alloc_file(struct file *file);
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void tty_add_file(struct tty_struct *tty, struct file *file);
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void tty_free_file(struct file *file);
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int tty_release(struct inode *inode, struct file *filp);
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#define tty_is_writelocked(tty) (mutex_is_locked(&tty->atomic_write_lock))
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int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty);
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void tty_ldisc_release(struct tty_struct *tty);
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int __must_check tty_ldisc_init(struct tty_struct *tty);
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void tty_ldisc_deinit(struct tty_struct *tty);
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extern int tty_ldisc_autoload;
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/* tty_audit.c */
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#ifdef CONFIG_AUDIT
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void tty_audit_add_data(struct tty_struct *tty, const void *data, size_t size);
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void tty_audit_tiocsti(struct tty_struct *tty, char ch);
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#else
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static inline void tty_audit_add_data(struct tty_struct *tty, const void *data,
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size_t size)
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{
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}
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static inline void tty_audit_tiocsti(struct tty_struct *tty, char ch)
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{
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}
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#endif
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ssize_t redirected_tty_write(struct kiocb *, struct iov_iter *);
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int tty_insert_flip_string_and_push_buffer(struct tty_port *port,
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const unsigned char *chars, size_t cnt);
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#endif
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