n_tty: move echoctl check and clean up logic

Check L_ECHOCTL before insertting a character in the echo buffer
(rather than as the buffer is processed), to be more consistent with
when all other L_ flags are checked.  Also cleaned up the related logic.

Note that this and the previous patch ("n_tty: honor opost flag for echoes")
were verified together by the reporters of the bug that patch addresses
(http://bugs.linuxbase.org/show_bug.cgi?id=2692), and the test now passes.

Signed-off-by: Joe Peterson <joe@skyrush.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 18 insertions, 28 deletions

diff --git a/drivers/char/n_tty.c b/drivers/char/n_tty.c
index e6eeeb234e5d..2e50f4dfc79c 100644
--- a/drivers/char/n_tty.c
+++ b/drivers/char/n_tty.c
@@ -576,33 +576,23 @@ static void process_echoes(struct tty_struct *tty)
                                 break;
 
                         default:
-                                if (iscntrl(op)) {
-                                        if (L_ECHOCTL(tty)) {
-                                                /*
-                                                 * Ensure there is enough space
-                                                 * for the whole ctrl pair.
-                                                 */
-                                                if (space < 2) {
-                                                        no_space_left = 1;
-                                                        break;
-                                                }
-                                                tty_put_char(tty, '^');
-                                                tty_put_char(tty, op ^ 0100);
-                                                tty->column += 2;
-                                                space -= 2;
-                                        } else {
-                                                if (!space) {
-                                                        no_space_left = 1;
-                                                        break;
-                                                }
-                                                tty_put_char(tty, op);
-                                                space--;
-                                        }
-                                }
                                 /*
-                                 * If above falls through, this was an
-                                 * undefined op.
+                                 * If the op is not a special byte code,
+                                 * it is a ctrl char tagged to be echoed
+                                 * as "^X" (where X is the letter
+                                 * representing the control char).
+                                 * Note that we must ensure there is
+                                 * enough space for the whole ctrl pair.
+                                 *
                                  */
+                                if (space < 2) {
+                                        no_space_left = 1;
+                                        break;
+                                }
+                                tty_put_char(tty, '^');
+                                tty_put_char(tty, op ^ 0100);
+                                tty->column += 2;
+                                space -= 2;
                                 cp += 2;
                                 nr -= 2;
                         }
@@ -809,8 +799,8 @@ static void echo_char_raw(unsigned char c, struct tty_struct *tty)
  *      Echo user input back onto the screen. This must be called only when
  *      L_ECHO(tty) is true. Called from the driver receive_buf path.
  *
- *      This variant tags control characters to be possibly echoed as
- *      as "^X" (where X is the letter representing the control char).
+ *      This variant tags control characters to be echoed as "^X"
+ *      (where X is the letter representing the control char).
  *
  *      Locking: echo_lock to protect the echo buffer
  */
@@ -823,7 +813,7 @@ static void echo_char(unsigned char c, struct tty_struct *tty)
                 add_echo_byte(ECHO_OP_START, tty);
                 add_echo_byte(ECHO_OP_START, tty);
         } else {
-                if (iscntrl(c) && c != '\t')
+                if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
                         add_echo_byte(ECHO_OP_START, tty);
                 add_echo_byte(c, tty);
         }