Use termios_rwsem to guarantee safe access to the termios values.
This is particularly important for N_TTY as changing certain termios
settings alters the mode of operation.
termios_rwsem must be dropped across throttle/unthrottle since
those functions claim the termios_rwsem exclusively (to guarantee
safe access to the termios and for mutual exclusion).
Signed-off-by: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
---
drivers/tty/n_tty.c | 35 ++++++++++++++++++++++++++++++-----
1 file changed, 30 insertions(+), 5 deletions(-)
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index fa463a9..985e0a3 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -1457,6 +1457,8 @@ static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
char buf[64];
unsigned long cpuflags;
+ down_read(&tty->termios_rwsem);
+
if (ldata->real_raw) {
raw_spin_lock_irqsave(&ldata->read_lock, cpuflags);
i = min(N_TTY_BUF_SIZE - read_cnt(ldata),
@@ -1514,13 +1516,19 @@ static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
* canonical mode and don't have a newline yet!
*/
while (1) {
+ int throttled;
tty_set_flow_change(tty, TTY_THROTTLE_SAFE);
if (receive_room(tty) >= TTY_THRESHOLD_THROTTLE)
break;
- if (!tty_throttle_safe(tty))
+ up_read(&tty->termios_rwsem);
+ throttled = tty_throttle_safe(tty);
+ down_read(&tty->termios_rwsem);
+ if (!throttled)
break;
}
__tty_set_flow_change(tty, 0);
+
+ up_read(&tty->termios_rwsem);
}
int is_ignored(int sig)
@@ -1932,6 +1940,8 @@ do_it_again:
if (c < 0)
return c;
+ down_read(&tty->termios_rwsem);
+
minimum = time = 0;
timeout = MAX_SCHEDULE_TIMEOUT;
if (!ldata->icanon) {
@@ -1953,11 +1963,15 @@ do_it_again:
* Internal serialization of reads.
*/
if (file->f_flags & O_NONBLOCK) {
- if (!mutex_trylock(&ldata->atomic_read_lock))
+ if (!mutex_trylock(&ldata->atomic_read_lock)) {
+ up_read(&tty->termios_rwsem);
return -EAGAIN;
+ }
} else {
- if (mutex_lock_interruptible(&ldata->atomic_read_lock))
+ if (mutex_lock_interruptible(&ldata->atomic_read_lock)) {
+ up_read(&tty->termios_rwsem);
return -ERESTARTSYS;
+ }
}
packet = tty->packet;
@@ -2007,7 +2021,11 @@ do_it_again:
break;
}
n_tty_set_room(tty);
+ up_read(&tty->termios_rwsem);
+
timeout = schedule_timeout(timeout);
+
+ down_read(&tty->termios_rwsem);
continue;
}
__set_current_state(TASK_RUNNING);
@@ -2046,13 +2064,17 @@ do_it_again:
* we won't get any more characters.
*/
while (1) {
+ int unthrottled;
tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
break;
if (!tty->count)
break;
n_tty_set_room(tty);
- if (!tty_unthrottle_safe(tty))
+ up_read(&tty->termios_rwsem);
+ unthrottled = tty_unthrottle_safe(tty);
+ down_read(&tty->termios_rwsem);
+ if (!unthrottled)
break;
}
__tty_set_flow_change(tty, 0);
@@ -2074,9 +2096,12 @@ do_it_again:
retval = size;
if (nr)
clear_bit(TTY_PUSH, &tty->flags);
- } else if (test_and_clear_bit(TTY_PUSH, &tty->flags))
+ } else if (test_and_clear_bit(TTY_PUSH, &tty->flags)) {
+ up_read(&tty->termios_rwsem);
goto do_it_again;
+ }
+ up_read(&tty->termios_rwsem);
n_tty_set_room(tty);
return retval;
}
--
1.8.1.2
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