linux-kernel - [PATCH] vt: incomplete initialization of vc_tab

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Message-ID: <20081018114929.GA25554@kroworsch.de>
Date:	Sat, 18 Oct 2008 13:49:31 +0200
From:	Wolfgang Kroworsch <wolfgang@...worsch.de>
To:	linux-kernel@...r.kernel.org
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: [PATCH] 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;

---

 drivers/char/vt.c |   10 ++++++++--
 1 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/char/vt.c b/drivers/char/vt.c
index d8f83e2..a5af607 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':
--
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