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

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

[Samuel Holland]

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@vger.kernel.org
Fixes: d8ae72427187 ("vt: preserve unicode values corresponding to screen characters")
Signed-off-by: Samuel Holland <samuel@sholland.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

Re: [PATCH] vt: Fix screen updates after CSI K sequences

[Nicolas Pitre]

On Sat, 3 Nov 2018, Samuel Holland wrote:

> 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.

There is already a slightly better fix submitted here:

https://lkml.org/lkml/2018/10/23/535


Nicolas