Fix OpenSSH pty regression on close
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@tuyoix.net>
Reported-by: Volth <openssh@volth.com>
Reported-by: Marc Aurele La France <tsi@tuyoix.net>
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@gmail.com>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c
index a946e49..aa80dc9 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
@@ -254,8 +231,6 @@
if (ld && ld->ops->flush_buffer)
ld->ops->flush_buffer(tty);
- check_other_closed(tty);
-
atomic_dec(&buf->priority);
mutex_unlock(&buf->lock);
}
@@ -522,10 +497,8 @@
*/
count = smp_load_acquire(&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;
@@ -614,3 +587,8 @@
{
return cancel_work_sync(&port->buf.work);
}
+
+void tty_buffer_flush_work(struct tty_port *port)
+{
+ flush_work(&port->buf.work);
+}