1 files changed, 10 insertions, 6 deletions

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 7cdd1eb9406c..0f74945af624 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -768,7 +768,7 @@ static size_t __process_echoes(struct tty_struct *tty)
          * data at the tail to prevent a subsequent overrun */
         while (ldata->echo_commit - tail >= ECHO_DISCARD_WATERMARK) {
                 if (echo_buf(ldata, tail) == ECHO_OP_START) {
-                        if (echo_buf(ldata, tail) == ECHO_OP_ERASE_TAB)
+                        if (echo_buf(ldata, tail + 1) == ECHO_OP_ERASE_TAB)
                                 tail += 3;
                         else
                                 tail += 2;
@@ -1998,7 +1998,10 @@ static int canon_copy_from_read_buf(struct tty_struct *tty,
                 found = 1;
 
         size = N_TTY_BUF_SIZE - tail;
-        n = (found + eol + size) & (N_TTY_BUF_SIZE - 1);
+        n = eol - tail;
+        if (n > 4096)
+                n += 4096;
+        n += found;
         c = n;
 
         if (found && read_buf(ldata, eol) == __DISABLED_CHAR) {
@@ -2243,18 +2246,19 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
                 if (time)
                         timeout = time;
         }
-        mutex_unlock(&ldata->atomic_read_lock);
-        remove_wait_queue(&tty->read_wait, &wait);
+        n_tty_set_room(tty);
+        up_read(&tty->termios_rwsem);
 
+        remove_wait_queue(&tty->read_wait, &wait);
         if (!waitqueue_active(&tty->read_wait))
                 ldata->minimum_to_wake = minimum;
 
+        mutex_unlock(&ldata->atomic_read_lock);
+
         __set_current_state(TASK_RUNNING);
         if (b - buf)
                 retval = b - buf;
 
-        n_tty_set_room(tty);
-        up_read(&tty->termios_rwsem);
         return retval;
 }