[PATCH] tty: Remove dead termiox code

Jann Horn
2020-12-03T02:04:41Z

set_termiox() and the TCGETX handler bail out with -EINVAL immediately
if ->termiox is NULL, but there are no code paths that can set
->termiox to a non-NULL pointer; and no such code paths seem to have
existed since the termiox mechanism was introduced back in
commit 1d65b4a088de ("tty: Add termiox") in v2.6.28.
Similarly, no driver actually implements .set_termiox; and it looks like
no driver ever has.

Delete this dead code; but leave the definition of struct termiox in the
UAPI headers intact.

Signed-off-by: Jann Horn <jannh@google.com>
---
drivers/tty/tty_ioctl.c | 61 ++------------------------------------
include/linux/tty.h | 1 -
include/linux/tty_driver.h | 9 ------
3 files changed, 2 insertions(+), 69 deletions(-)

diff --git a/drivers/tty/tty_ioctl.c b/drivers/tty/tty_ioctl.c
index e18f318586ab..4de1c6ddb8ff 100644
--- a/drivers/tty/tty_ioctl.c
+++ b/drivers/tty/tty_ioctl.c
@@ -443,51 +443,6 @@ static int get_termio(struct tty_struct *tty, struct termio __user *termio)
return 0;
}

-
-#ifdef TCGETX
-
-/**
- * set_termiox - set termiox fields if possible
- * @tty: terminal
- * @arg: termiox structure from user
- * @opt: option flags for ioctl type
- *
- * Implement the device calling points for the SYS5 termiox ioctl
- * interface in Linux
- */
-
-static int set_termiox(struct tty_struct *tty, void __user *arg, int opt)
-{
- struct termiox tnew;
- struct tty_ldisc *ld;
-
- if (tty->termiox == NULL)
- return -EINVAL;
- if (copy_from_user(&tnew, arg, sizeof(struct termiox)))
- return -EFAULT;
-
- ld = tty_ldisc_ref(tty);
- if (ld != NULL) {
- if ((opt & TERMIOS_FLUSH) && ld->ops->flush_buffer)
- ld->ops->flush_buffer(tty);
- tty_ldisc_deref(ld);
- }
- if (opt & TERMIOS_WAIT) {
- tty_wait_until_sent(tty, 0);
- if (signal_pending(current))
- return -ERESTARTSYS;
- }
-
- down_write(&tty->termios_rwsem);
- if (tty->ops->set_termiox)
- tty->ops->set_termiox(tty, &tnew);
- up_write(&tty->termios_rwsem);
- return 0;
-}
-
-#endif
-
-
#ifdef TIOCGETP
/*
* These are deprecated, but there is limited support..
@@ -815,23 +770,11 @@ int tty_mode_ioctl(struct tty_struct *tty, struct file *file,
return ret;
#endif
#ifdef TCGETX
- case TCGETX: {
- struct termiox ktermx;
- if (real_tty->termiox == NULL)
- return -EINVAL;
- down_read(&real_tty->termios_rwsem);
- memcpy(&ktermx, real_tty->termiox, sizeof(struct termiox));
- up_read(&real_tty->termios_rwsem);
- if (copy_to_user(p, &ktermx, sizeof(struct termiox)))
- ret = -EFAULT;
- return ret;
- }
+ case TCGETX:
case TCSETX:
- return set_termiox(real_tty, p, 0);
case TCSETXW:
- return set_termiox(real_tty, p, TERMIOS_WAIT);
case TCSETXF:
- return set_termiox(real_tty, p, TERMIOS_FLUSH);
+ return -EINVAL;
#endif
case TIOCGSOFTCAR:
copy_termios(real_tty, &kterm);
diff --git a/include/linux/tty.h b/include/linux/tty.h
index a99e9b8e4e31..52f5544bcd85 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -303,7 +303,6 @@ struct tty_struct {
spinlock_t flow_lock;
/* Termios values are protected by the termios rwsem */
struct ktermios termios, termios_locked;
- struct termiox *termiox; /* May be NULL for unsupported */
char name[64];
struct pid *pgrp; /* Protected by ctrl lock */
struct pid *session;
diff --git a/include/linux/tty_driver.h b/include/linux/tty_driver.h
index 358446247ccd..61c3372d3f32 100644
--- a/include/linux/tty_driver.h
+++ b/include/linux/tty_driver.h
@@ -224,14 +224,6 @@
* line). See tty_do_resize() if you need to wrap the standard method
* in your own logic - the usual case.
*
- * void (*set_termiox)(struct tty_struct *tty, struct termiox *new);
- *
- * Called when the device receives a termiox based ioctl. Passes down
- * the requested data from user space. This method will not be invoked
- * unless the tty also has a valid tty->termiox pointer.
- *
- * Optional: Called under the termios lock
- *
* int (*get_icount)(struct tty_struct *tty, struct serial_icounter *icount);
*
* Called when the device receives a TIOCGICOUNT ioctl. Passed a kernel
@@ -285,7 +277,6 @@ struct tty_operations {
int (*tiocmset)(struct tty_struct *tty,
unsigned int set, unsigned int clear);
int (*resize)(struct tty_struct *tty, struct winsize *ws);
- int (*set_termiox)(struct tty_struct *tty, struct termiox *tnew);
int (*get_icount)(struct tty_struct *tty,
struct serial_icounter_struct *icount);
int (*get_serial)(struct tty_struct *tty, struct serial_struct *p);

base-commit: 3bb61aa61828499a7d0f5e560051625fd02ae7e4
--
2.29.2.576.ga3fc446d84-goog