vt: incomplete initialization of vc_tab_stop

Problem 1 (see patch below):
  vc_tab_stop is declared as an array of 8 unsigned ints in struct
  vc_data in include/linux/console_struct.h .
  In drivers/char/vt.c only 5 of these 8 unsigned ints get initialized
  leading to unintended tabulator placement on displays with more than
  160 columns text.

Problem 2 (open):
  Upcoming displays will have more than 256 columns of text leading to
  invalid memory access in drivers/char/vt.c during tabulator
  calculations:
    if (vc->vc_tab_stop[vc->vc_x >> 5] & (1 << (vc->vc_x & 31)))
	break;

Signed-off-by: Wolfgang Kroworsch <wolfgang@kroworsch.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 2 deletions

diff --git a/drivers/char/vt.c b/drivers/char/vt.c
index d8f83e26e4a4..a5af6072e2b3 100644
--- a/drivers/char/vt.c
+++ b/drivers/char/vt.c
@@ -1644,7 +1644,10 @@ static void reset_terminal(struct vc_data *vc, int do_clear)
         vc->vc_tab_stop[1]      =
         vc->vc_tab_stop[2]      =
         vc->vc_tab_stop[3]      =
-        vc->vc_tab_stop[4]      = 0x01010101;
+        vc->vc_tab_stop[4]      =
+        vc->vc_tab_stop[5]      =
+        vc->vc_tab_stop[6]      =
+        vc->vc_tab_stop[7]      = 0x01010101;
 
         vc->vc_bell_pitch = DEFAULT_BELL_PITCH;
         vc->vc_bell_duration = DEFAULT_BELL_DURATION;
@@ -1935,7 +1938,10 @@ static void do_con_trol(struct tty_struct *tty, struct vc_data *vc, int c)
                                         vc->vc_tab_stop[1] =
                                         vc->vc_tab_stop[2] =
                                         vc->vc_tab_stop[3] =
-                                        vc->vc_tab_stop[4] = 0;
+                                        vc->vc_tab_stop[4] =
+                                        vc->vc_tab_stop[5] =
+                                        vc->vc_tab_stop[6] =
+                                        vc->vc_tab_stop[7] = 0;
                         }
                         return;
                 case 'm':