tty: flush flip buffer on ldisc input queue flush
Flush the tty flip buffer when the line discipline input queue is flushed,
including the user call tcflush(TCIFLUSH/TCIOFLUSH). This prevents
unexpected stale data after a user application calls tcflush().
Signed-off-by: Alan Cox <alan@redhat.com>
Cc: Antonino Ingargiola <tritemio@gmail.com>
Signed-off-by: Paul Fulghum <paulkf@microgate.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index bc84995..75d2a46 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -369,6 +369,29 @@
}
/**
+ * tty_buffer_flush - flush full tty buffers
+ * @tty: tty to flush
+ *
+ * flush all the buffers containing receive data
+ *
+ * Locking: none
+ */
+
+static void tty_buffer_flush(struct tty_struct *tty)
+{
+ struct tty_buffer *thead;
+ unsigned long flags;
+
+ spin_lock_irqsave(&tty->buf.lock, flags);
+ while((thead = tty->buf.head) != NULL) {
+ tty->buf.head = thead->next;
+ tty_buffer_free(tty, thead);
+ }
+ tty->buf.tail = NULL;
+ spin_unlock_irqrestore(&tty->buf.lock, flags);
+}
+
+/**
* tty_buffer_find - find a free tty buffer
* @tty: tty owning the buffer
* @size: characters wanted
@@ -1248,6 +1271,7 @@
ld->flush_buffer(tty);
tty_ldisc_deref(ld);
}
+ tty_buffer_flush(tty);
}
EXPORT_SYMBOL_GPL(tty_ldisc_flush);
@@ -3350,6 +3374,15 @@
case TIOCMBIC:
case TIOCMBIS:
return tty_tiocmset(tty, file, cmd, p);
+ case TCFLSH:
+ switch (arg) {
+ case TCIFLUSH:
+ case TCIOFLUSH:
+ /* flush tty buffer and allow ldisc to process ioctl */
+ tty_buffer_flush(tty);
+ break;
+ }
+ break;
}
if (tty->driver->ioctl) {
retval = (tty->driver->ioctl)(tty, file, cmd, arg);