linux-kernel - [PATCH 3.2 144/153] tty: vt: fix up tabstops properly

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Message-ID: <lsq.1527677562.502313133@decadent.org.uk>
Date:   Wed, 30 May 2018 11:52:42 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Linus Torvalds" <torvalds@...ux-foundation.org>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "James Holderness" <j4_james@...mail.com>
Subject: [PATCH 3.2 144/153] tty: vt: fix up tabstops properly

3.2.102-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Linus Torvalds <torvalds@...ux-foundation.org>

commit f1869a890cdedb92a3fab969db5d0fd982850273 upstream.

Tabs on a console with long lines do not wrap properly, so correctly
account for the line length when computing the tab placement location.

Reported-by: James Holderness <j4_james@...mail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/tty/vt/vt.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -1676,7 +1676,7 @@ static void reset_terminal(struct vc_dat
 	default_attr(vc);
 	update_attr(vc);
 
-	vc->vc_tab_stop[0]	= 0x01010100;
+	vc->vc_tab_stop[0]	=
 	vc->vc_tab_stop[1]	=
 	vc->vc_tab_stop[2]	=
 	vc->vc_tab_stop[3]	=
@@ -1715,7 +1715,7 @@ static void do_con_trol(struct tty_struc
 		vc->vc_pos -= (vc->vc_x << 1);
 		while (vc->vc_x < vc->vc_cols - 1) {
 			vc->vc_x++;
-			if (vc->vc_tab_stop[vc->vc_x >> 5] & (1 << (vc->vc_x & 31)))
+			if (vc->vc_tab_stop[7 & (vc->vc_x >> 5)] & (1 << (vc->vc_x & 31)))
 				break;
 		}
 		vc->vc_pos += (vc->vc_x << 1);
@@ -1775,7 +1775,7 @@ static void do_con_trol(struct tty_struc
 			lf(vc);
 			return;
 		case 'H':
-			vc->vc_tab_stop[vc->vc_x >> 5] |= (1 << (vc->vc_x & 31));
+			vc->vc_tab_stop[7 & (vc->vc_x >> 5)] |= (1 << (vc->vc_x & 31));
 			return;
 		case 'Z':
 			respond_ID(tty);
@@ -1968,7 +1968,7 @@ static void do_con_trol(struct tty_struc
 			return;
 		case 'g':
 			if (!vc->vc_par[0])
-				vc->vc_tab_stop[vc->vc_x >> 5] &= ~(1 << (vc->vc_x & 31));
+				vc->vc_tab_stop[7 & (vc->vc_x >> 5)] &= ~(1 << (vc->vc_x & 31));
 			else if (vc->vc_par[0] == 3) {
 				vc->vc_tab_stop[0] =
 					vc->vc_tab_stop[1] =