linux-kernel - [PATCH] vt: Fix screen updates after CSI K sequences

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Message-Id: <20181103174831.1666-1-samuel@sholland.org>
Date:   Sat,  3 Nov 2018 12:48:31 -0500
From:   Samuel Holland <samuel@...lland.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        Nicolas Pitre <nicolas.pitre@...aro.org>
Cc:     Adam Borowski <kilobyte@...band.pl>,
        Samuel Holland <samuel@...lland.org>,
        Mike Frysinger <vapier@...omium.org>,
        Alexander Potapenko <glider@...gle.com>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: [PATCH] vt: Fix screen updates after CSI K sequences

In d8ae72427187, start was changed to point to the character under the
cursor, instead of the beginning of the cleared area. The offset was
correctly applied when clearing the backing buffer, but not when
updating the framebuffer region. Fix this by having start point once
again to the beginning of the cleared area.

Cc: stable@...r.kernel.org
Fixes: d8ae72427187 ("vt: preserve unicode values corresponding to screen characters")
Signed-off-by: Samuel Holland <samuel@...lland.org>
---
 drivers/tty/vt/vt.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 5f1183b0b89d..be7bc83d6c41 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -1528,7 +1528,7 @@ static void csi_J(struct vc_data *vc, int vpar)
 static void csi_K(struct vc_data *vc, int vpar)
 {
 	unsigned int count;
-	unsigned short *start = (unsigned short *)vc->vc_pos;
+	unsigned short *start;
 	int offset;
 
 	switch (vpar) {
@@ -1548,7 +1548,8 @@ static void csi_K(struct vc_data *vc, int vpar)
 			return;
 	}
 	vc_uniscr_clear_line(vc, vc->vc_x + offset, count);
-	scr_memsetw(start + offset, vc->vc_video_erase_char, 2 * count);
+	start = (unsigned short *)vc->vc_pos + offset;
+	scr_memsetw(start, vc->vc_video_erase_char, 2 * count);
 	vc->vc_need_wrap = 0;
 	if (con_should_update(vc))
 		do_update_region(vc, (unsigned long) start, count);
-- 
2.18.1