On Sat, 30 Mar 2019, Mikulas Patocka wrote:

Hi

The patch a6dbe442755999960ca54a9b8ecfd9606be0ea75 ("vt: perform safe console erase in the right order") introduces a bug.

---

drivers/tty/vt/vt.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-5.0.5/drivers/tty/vt/vt.c

--- linux-5.0.5.orig/drivers/tty/vt/vt.c 2019-03-30 19:29:26.000000000 +0100 +++ linux-5.0.5/drivers/tty/vt/vt.c 2019-03-30 19:30:50.000000000 +0100 @@ -1518,7 +1518,7 @@ static void csi_J(struct vc_data *vc, in return; } scr_memsetw(start, vc->vc_video_erase_char, 2 * count);

• update_region(vc, (unsigned long) start, count);

• do_update_region(vc, (unsigned long) start, count);

^^^^ this is wrong too - it will clear the screen if \e[2J is printed on inactive console. We need to use con_should_update(vc), just like it was before:

The patch a6dbe442755999960ca54a9b8ecfd9606be0ea75 ("vt: perform safe console erase in the right order") introduces a bug.

In order to reproduce the bug - use framebuffer console with the AMDGPU driver - type "links" to start the console www browser - press 'q' and space to exit links

--- now, the cursor line will be permanently visible in the center of the screen. It will stay there until something overwrites it.

Before the patch, there was a call to do_update_region, the patch changes it to update_region - and this seems to cause the bug with the cursor.

The bug goes away if we change update_region back to do_update_region.

Signed-off-by: Mikulas Patocka mpatocka@redhat.com Cc: stable@vger.kernel.org Fixes: a6dbe4427559 ("vt: perform safe console erase in the right order")

--- drivers/tty/vt/vt.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)

Index: linux-5.0.5/drivers/tty/vt/vt.c =================================================================== --- linux-5.0.5.orig/drivers/tty/vt/vt.c 2019-03-30 19:29:26.000000000 +0100 +++ linux-5.0.5/drivers/tty/vt/vt.c 2019-03-31 13:06:24.000000000 +0200 @@ -1518,7 +1518,8 @@ static void csi_J(struct vc_data *vc, in return; } scr_memsetw(start, vc->vc_video_erase_char, 2 * count); - update_region(vc, (unsigned long) start, count); + if (con_should_update(vc)) + do_update_region(vc, (unsigned long) start, count); vc->vc_need_wrap = 0; }

On Sun, Mar 31, 2019 at 04:18:01PM -0400, Mikulas Patocka wrote:

On Sat, 30 Mar 2019, Mikulas Patocka wrote:

...

Hi

The patch a6dbe442755999960ca54a9b8ecfd9606be0ea75 ("vt: perform safe console erase in the right order") introduces a bug.

---

drivers/tty/vt/vt.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-5.0.5/drivers/tty/vt/vt.c

--- linux-5.0.5.orig/drivers/tty/vt/vt.c 2019-03-30 19:29:26.000000000 +0100 +++ linux-5.0.5/drivers/tty/vt/vt.c 2019-03-30 19:30:50.000000000 +0100 @@ -1518,7 +1518,7 @@ static void csi_J(struct vc_data *vc, in return; } scr_memsetw(start, vc->vc_video_erase_char, 2 * count);

• update_region(vc, (unsigned long) start, count);

• do_update_region(vc, (unsigned long) start, count);

^^^^ this is wrong too - it will clear the screen if \e[2J is printed on inactive console. We need to use con_should_update(vc), just like it was before:

The patch a6dbe442755999960ca54a9b8ecfd9606be0ea75 ("vt: perform safe console erase in the right order") introduces a bug.

In order to reproduce the bug

• use framebuffer console with the AMDGPU driver
• type "links" to start the console www browser
• press 'q' and space to exit links

--- now, the cursor line will be permanently visible in the center of the screen. It will stay there until something overwrites it.

Before the patch, there was a call to do_update_region, the patch changes it to update_region - and this seems to cause the bug with the cursor.

The bug goes away if we change update_region back to do_update_region.

Signed-off-by: Mikulas Patocka mpatocka@redhat.com Cc: stable@vger.kernel.org Fixes: a6dbe4427559 ("vt: perform safe console erase in the right order")

---

drivers/tty/vt/vt.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)

Index: linux-5.0.5/drivers/tty/vt/vt.c

--- linux-5.0.5.orig/drivers/tty/vt/vt.c 2019-03-30 19:29:26.000000000 +0100 +++ linux-5.0.5/drivers/tty/vt/vt.c 2019-03-31 13:06:24.000000000 +0200 @@ -1518,7 +1518,8 @@ static void csi_J(struct vc_data *vc, in return; } scr_memsetw(start, vc->vc_video_erase_char, 2 * count);

• update_region(vc, (unsigned long) start, count);

• if (con_should_update(vc))

• do_update_region(vc, (unsigned long) start, count);
  

  vc->vc_need_wrap = 0;

}

Can you resend this, with the ack, in a format that I can apply it in?

thanks,

greg k-h

On Tue, Apr 16, 2019 at 10:53:54AM -0400, Nicolas Pitre wrote:

On Tue, 16 Apr 2019, Greg Kroah-Hartman wrote:

...

On Sun, Mar 31, 2019 at 04:18:01PM -0400, Mikulas Patocka wrote:

...

On Sat, 30 Mar 2019, Mikulas Patocka wrote:

...

Hi

The patch a6dbe442755999960ca54a9b8ecfd9606be0ea75 ("vt: perform safe console erase in the right order") introduces a bug.

---

drivers/tty/vt/vt.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-5.0.5/drivers/tty/vt/vt.c

--- linux-5.0.5.orig/drivers/tty/vt/vt.c 2019-03-30 19:29:26.000000000 +0100 +++ linux-5.0.5/drivers/tty/vt/vt.c 2019-03-30 19:30:50.000000000 +0100 @@ -1518,7 +1518,7 @@ static void csi_J(struct vc_data *vc, in return; } scr_memsetw(start, vc->vc_video_erase_char, 2 * count);

• update_region(vc, (unsigned long) start, count);

• do_update_region(vc, (unsigned long) start, count);

^^^^ this is wrong too - it will clear the screen if \e[2J is printed on inactive console. We need to use con_should_update(vc), just like it was before:

The patch a6dbe442755999960ca54a9b8ecfd9606be0ea75 ("vt: perform safe console erase in the right order") introduces a bug.

In order to reproduce the bug

• use framebuffer console with the AMDGPU driver
• type "links" to start the console www browser
• press 'q' and space to exit links

--- now, the cursor line will be permanently visible in the center of the screen. It will stay there until something overwrites it.

Before the patch, there was a call to do_update_region, the patch changes it to update_region - and this seems to cause the bug with the cursor.

The bug goes away if we change update_region back to do_update_region.

Signed-off-by: Mikulas Patocka mpatocka@redhat.com Cc: stable@vger.kernel.org Fixes: a6dbe4427559 ("vt: perform safe console erase in the right order")

---

drivers/tty/vt/vt.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)

Index: linux-5.0.5/drivers/tty/vt/vt.c

--- linux-5.0.5.orig/drivers/tty/vt/vt.c 2019-03-30 19:29:26.000000000 +0100 +++ linux-5.0.5/drivers/tty/vt/vt.c 2019-03-31 13:06:24.000000000 +0200 @@ -1518,7 +1518,8 @@ static void csi_J(struct vc_data *vc, in return; } scr_memsetw(start, vc->vc_video_erase_char, 2 * count);

• update_region(vc, (unsigned long) start, count);

• if (con_should_update(vc))

• do_update_region(vc, (unsigned long) start, count);
  

  vc->vc_need_wrap = 0;

}

Can you resend this, with the ack, in a format that I can apply it in?

I did resend that patch to you with a proper changelog on April 4th. Subject is "[PATCH] fix cursor when clearing the screen".

Ah, sorry, I see it now, it's burried in my "to-review" queue. Will go apply it now, thanks!

greg k-h