4.2.8-ckt12 -stable review patch. If anyone has any objections, please let me know. ---8<------------------------------------------------------------ From: Brian Bloniarz <brian.bloniarz@xxxxxxxxx> commit 0f40fbbcc34e093255a2b2d70b6b0fb48c3f39aa upstream. OpenSSH expects the (non-blocking) read() of pty master to return EAGAIN only if it has received all of the slave-side output after it has received SIGCHLD. This used to work on pre-3.12 kernels. This fix effectively forces non-blocking read() and poll() to block for parallel i/o to complete for all ttys. It also unwinds these changes: 1) f8747d4a466ab2cafe56112c51b3379f9fdb7a12 tty: Fix pty master read() after slave closes 2) 52bce7f8d4fc633c9a9d0646eef58ba6ae9a3b73 pty, n_tty: Simplify input processing on final close 3) 1a48632ffed61352a7810ce089dc5a8bcd505a60 pty: Fix input race when closing Inspired by analysis and patch from Marc Aurele La France <tsi@xxxxxxxxxx> Reported-by: Volth <openssh@xxxxxxxxx> Reported-by: Marc Aurele La France <tsi@xxxxxxxxxx> BugLink: https://bugzilla.mindrot.org/show_bug.cgi?id=52 BugLink: https://bugzilla.mindrot.org/show_bug.cgi?id=2492 Signed-off-by: Brian Bloniarz <brian.bloniarz@xxxxxxxxx> Reviewed-by: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx> --- Documentation/serial/tty.txt | 3 -- drivers/tty/n_hdlc.c | 4 +-- drivers/tty/n_tty.c | 70 +++++++++++++++++++++----------------------- drivers/tty/pty.c | 4 +-- drivers/tty/tty_buffer.c | 34 ++++----------------- include/linux/tty.h | 2 +- 6 files changed, 43 insertions(+), 74 deletions(-) diff --git a/Documentation/serial/tty.txt b/Documentation/serial/tty.txt index 973c8ad..849e81a 100644 --- a/Documentation/serial/tty.txt +++ b/Documentation/serial/tty.txt @@ -195,9 +195,6 @@ TTY_IO_ERROR If set, causes all subsequent userspace read/write TTY_OTHER_CLOSED Device is a pty and the other side has closed. -TTY_OTHER_DONE Device is a pty and the other side has closed and - all pending input processing has been completed. - TTY_NO_WRITE_SPLIT Prevent driver from splitting up writes into smaller chunks. diff --git a/drivers/tty/n_hdlc.c b/drivers/tty/n_hdlc.c index bbc4ce6..644ddb8 100644 --- a/drivers/tty/n_hdlc.c +++ b/drivers/tty/n_hdlc.c @@ -600,7 +600,7 @@ static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file, add_wait_queue(&tty->read_wait, &wait); for (;;) { - if (test_bit(TTY_OTHER_DONE, &tty->flags)) { + if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) { ret = -EIO; break; } @@ -828,7 +828,7 @@ static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp, /* set bits for operations that won't block */ if (n_hdlc->rx_buf_list.head) mask |= POLLIN | POLLRDNORM; /* readable */ - if (test_bit(TTY_OTHER_DONE, &tty->flags)) + if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) mask |= POLLHUP; if (tty_hung_up_p(filp)) mask |= POLLHUP; diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c index 4e27ab9..a717fdb 100644 --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -1959,18 +1959,6 @@ static inline int input_available_p(struct tty_struct *tty, int poll) return ldata->commit_head - ldata->read_tail >= amt; } -static inline int check_other_done(struct tty_struct *tty) -{ - int done = test_bit(TTY_OTHER_DONE, &tty->flags); - if (done) { - /* paired with cmpxchg() in check_other_closed(); ensures - * read buffer head index is not stale - */ - smp_mb__after_atomic(); - } - return done; -} - /** * copy_from_read_buf - copy read data directly * @tty: terminal device @@ -2188,7 +2176,7 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, struct n_tty_data *ldata = tty->disc_data; unsigned char __user *b = buf; DEFINE_WAIT_FUNC(wait, woken_wake_function); - int c, done; + int c; int minimum, time; ssize_t retval = 0; long timeout; @@ -2256,32 +2244,35 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, ((minimum - (b - buf)) >= 1)) ldata->minimum_to_wake = (minimum - (b - buf)); - done = check_other_done(tty); - if (!input_available_p(tty, 0)) { - if (done) { - retval = -EIO; - break; - } - if (tty_hung_up_p(file)) - break; - if (!timeout) - break; - if (file->f_flags & O_NONBLOCK) { - retval = -EAGAIN; - break; - } - if (signal_pending(current)) { - retval = -ERESTARTSYS; - break; - } up_read(&tty->termios_rwsem); + tty_buffer_flush_work(tty->port); + down_read(&tty->termios_rwsem); + if (!input_available_p(tty, 0)) { + if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) { + retval = -EIO; + break; + } + if (tty_hung_up_p(file)) + break; + if (!timeout) + break; + if (file->f_flags & O_NONBLOCK) { + retval = -EAGAIN; + break; + } + if (signal_pending(current)) { + retval = -ERESTARTSYS; + break; + } + up_read(&tty->termios_rwsem); - timeout = wait_woken(&wait, TASK_INTERRUPTIBLE, - timeout); + timeout = wait_woken(&wait, TASK_INTERRUPTIBLE, + timeout); - down_read(&tty->termios_rwsem); - continue; + down_read(&tty->termios_rwsem); + continue; + } } if (ldata->icanon && !L_EXTPROC(tty)) { @@ -2463,12 +2454,17 @@ static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file, poll_wait(file, &tty->read_wait, wait); poll_wait(file, &tty->write_wait, wait); - if (check_other_done(tty)) - mask |= POLLHUP; if (input_available_p(tty, 1)) mask |= POLLIN | POLLRDNORM; + else { + tty_buffer_flush_work(tty->port); + if (input_available_p(tty, 1)) + mask |= POLLIN | POLLRDNORM; + } if (tty->packet && tty->link->ctrl_status) mask |= POLLPRI | POLLIN | POLLRDNORM; + if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) + mask |= POLLHUP; if (tty_hung_up_p(file)) mask |= POLLHUP; if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) { diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c index 254c183..b1f78aa 100644 --- a/drivers/tty/pty.c +++ b/drivers/tty/pty.c @@ -54,7 +54,7 @@ static void pty_close(struct tty_struct *tty, struct file *filp) if (!tty->link) return; set_bit(TTY_OTHER_CLOSED, &tty->link->flags); - tty_flip_buffer_push(tty->link->port); + wake_up_interruptible(&tty->link->read_wait); wake_up_interruptible(&tty->link->write_wait); if (tty->driver->subtype == PTY_TYPE_MASTER) { set_bit(TTY_OTHER_CLOSED, &tty->flags); @@ -242,9 +242,7 @@ static int pty_open(struct tty_struct *tty, struct file *filp) goto out; clear_bit(TTY_IO_ERROR, &tty->flags); - /* TTY_OTHER_CLOSED must be cleared before TTY_OTHER_DONE */ clear_bit(TTY_OTHER_CLOSED, &tty->link->flags); - clear_bit(TTY_OTHER_DONE, &tty->link->flags); set_bit(TTY_THROTTLED, &tty->flags); return 0; diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c index a0ee0bf..d7b9a52 100644 --- a/drivers/tty/tty_buffer.c +++ b/drivers/tty/tty_buffer.c @@ -37,29 +37,6 @@ #define TTY_BUFFER_PAGE (((PAGE_SIZE - sizeof(struct tty_buffer)) / 2) & ~0xFF) -/* - * If all tty flip buffers have been processed by flush_to_ldisc() or - * dropped by tty_buffer_flush(), check if the linked pty has been closed. - * If so, wake the reader/poll to process - */ -static inline void check_other_closed(struct tty_struct *tty) -{ - unsigned long flags, old; - - /* transition from TTY_OTHER_CLOSED => TTY_OTHER_DONE must be atomic */ - for (flags = ACCESS_ONCE(tty->flags); - test_bit(TTY_OTHER_CLOSED, &flags); - ) { - old = flags; - __set_bit(TTY_OTHER_DONE, &flags); - flags = cmpxchg(&tty->flags, old, flags); - if (old == flags) { - wake_up_interruptible(&tty->read_wait); - break; - } - } -} - /** * tty_buffer_lock_exclusive - gain exclusive access to buffer * tty_buffer_unlock_exclusive - release exclusive access @@ -251,8 +228,6 @@ void tty_buffer_flush(struct tty_struct *tty, struct tty_ldisc *ld) if (ld && ld->ops->flush_buffer) ld->ops->flush_buffer(tty); - check_other_closed(tty); - atomic_dec(&buf->priority); mutex_unlock(&buf->lock); } @@ -496,10 +471,8 @@ static void flush_to_ldisc(struct work_struct *work) smp_rmb(); count = head->commit - head->read; if (!count) { - if (next == NULL) { - check_other_closed(tty); + if (next == NULL) break; - } buf->head = next; tty_buffer_free(port, head); continue; @@ -587,3 +560,8 @@ bool tty_buffer_cancel_work(struct tty_port *port) { return cancel_work_sync(&port->buf.work); } + +void tty_buffer_flush_work(struct tty_port *port) +{ + flush_work(&port->buf.work); +} diff --git a/include/linux/tty.h b/include/linux/tty.h index 223d905..d28c904 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -339,7 +339,6 @@ struct tty_file_private { #define TTY_EXCLUSIVE 3 /* Exclusive open mode */ #define TTY_DEBUG 4 /* Debugging */ #define TTY_DO_WRITE_WAKEUP 5 /* Call write_wakeup after queuing new */ -#define TTY_OTHER_DONE 6 /* Closed pty has completed input processing */ #define TTY_LDISC_OPEN 11 /* Line discipline is open */ #define TTY_PTY_LOCK 16 /* pty private */ #define TTY_NO_WRITE_SPLIT 17 /* Preserve write boundaries to driver */ @@ -469,6 +468,7 @@ extern void tty_buffer_init(struct tty_port *port); extern void tty_buffer_set_lock_subclass(struct tty_port *port); extern bool tty_buffer_restart_work(struct tty_port *port); extern bool tty_buffer_cancel_work(struct tty_port *port); +extern void tty_buffer_flush_work(struct tty_port *port); extern speed_t tty_termios_baud_rate(struct ktermios *termios); extern speed_t tty_termios_input_baud_rate(struct ktermios *termios); extern void tty_termios_encode_baud_rate(struct ktermios *termios, -- 2.7.4 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html