1 files changed, 61 insertions, 12 deletions

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index efc72104c840..640c9e871044 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -1220,21 +1220,34 @@ n_tty_receive_signal_char(struct tty_struct *tty, int signal, unsigned char c)
 		process_echoes(tty);
 }
 
+static bool n_tty_is_char_flow_ctrl(struct tty_struct *tty, unsigned char c)
+{
+	return c == START_CHAR(tty) || c == STOP_CHAR(tty);
+}
+
+/* Returns true if c is consumed as flow-control character */
+static bool n_tty_receive_char_flow_ctrl(struct tty_struct *tty, unsigned char c)
+{
+	if (!n_tty_is_char_flow_ctrl(tty, c))
+		return false;
+
+	if (c == START_CHAR(tty)) {
+		start_tty(tty);
+		process_echoes(tty);
+		return true;
+	}
+
+	/* STOP_CHAR */
+	stop_tty(tty);
+	return true;
+}
+
 static void n_tty_receive_char_special(struct tty_struct *tty, unsigned char c)
 {
 	struct n_tty_data *ldata = tty->disc_data;
 
-	if (I_IXON(tty)) {
-		if (c == START_CHAR(tty)) {
-			start_tty(tty);
-			process_echoes(tty);
-			return;
-		}
-		if (c == STOP_CHAR(tty)) {
-			stop_tty(tty);
-			return;
-		}
-	}
+	if (I_IXON(tty) && n_tty_receive_char_flow_ctrl(tty, c))
+		return;
 
 	if (L_ISIG(tty)) {
 		if (c == INTR_CHAR(tty)) {
@@ -1975,6 +1988,35 @@ static bool canon_copy_from_read_buf(struct tty_struct *tty,
 	return ldata->read_tail != canon_head;
 }
 
+/*
+ * If we finished a read at the exact location of an
+ * EOF (special EOL character that's a __DISABLED_CHAR)
+ * in the stream, silently eat the EOF.
+ */
+static void canon_skip_eof(struct tty_struct *tty)
+{
+	struct n_tty_data *ldata = tty->disc_data;
+	size_t tail, canon_head;
+
+	canon_head = smp_load_acquire(&ldata->canon_head);
+	tail = ldata->read_tail;
+
+	// No data?
+	if (tail == canon_head)
+		return;
+
+	// See if the tail position is EOF in the circular buffer
+	tail &= (N_TTY_BUF_SIZE - 1);
+	if (!test_bit(tail, ldata->read_flags))
+		return;
+	if (read_buf(ldata, tail) != __DISABLED_CHAR)
+		return;
+
+	// Clear the EOL bit, skip the EOF char.
+	clear_bit(tail, ldata->read_flags);
+	smp_store_release(&ldata->read_tail, ldata->read_tail + 1);
+}
+
 /**
  * job_control		-	check job control
  * @tty: tty
@@ -2045,7 +2087,14 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
 	 */
 	if (*cookie) {
 		if (ldata->icanon && !L_EXTPROC(tty)) {
-			if (canon_copy_from_read_buf(tty, &kb, &nr))
+			/*
+			 * If we have filled the user buffer, see
+			 * if we should skip an EOF character before
+			 * releasing the lock and returning done.
+			 */
+			if (!nr)
+				canon_skip_eof(tty);
+			else if (canon_copy_from_read_buf(tty, &kb, &nr))
 				return kb - kbuf;
 		} else {
 			if (copy_from_read_buf(tty, &kb, &nr))