If finalize chardev-msmouse or chardev-wctable is called immediately after
init it cases QEMU to crash with segfault. This happens because of
QTAILQ_REMOVE in qemu_input_handler_unregister tries to dereference
NULL pointer.
For instance, this error can be reproduced via `qom-list-properties`
command.

Signed-off-by: Maksim Davydov <davydov-max@yandex-team.ru>
---
 chardev/msmouse.c  | 4 +++-
 chardev/wctablet.c | 4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/chardev/msmouse.c b/chardev/msmouse.c
index eb9231dcdb..2cc1b16561 100644
--- a/chardev/msmouse.c
+++ b/chardev/msmouse.c
@@ -146,7 +146,9 @@ static void char_msmouse_finalize(Object *obj)
 {
     MouseChardev *mouse = MOUSE_CHARDEV(obj);
 
-    qemu_input_handler_unregister(mouse->hs);
+    if (mouse->hs) {
+        qemu_input_handler_unregister(mouse->hs);
+    }
 }
 
 static QemuInputHandler msmouse_handler = {
diff --git a/chardev/wctablet.c b/chardev/wctablet.c
index e8b292c43c..43bdf6b608 100644
--- a/chardev/wctablet.c
+++ b/chardev/wctablet.c
@@ -319,7 +319,9 @@ static void wctablet_chr_finalize(Object *obj)
 {
     TabletChardev *tablet = WCTABLET_CHARDEV(obj);
 
-    qemu_input_handler_unregister(tablet->hs);
+    if (tablet->hs) {
+        qemu_input_handler_unregister(tablet->hs);
+    }
 }
 
 static void wctablet_chr_open(Chardev *chr,
-- 
2.25.1

On 8/25/22 19:52, Maksim Davydov wrote:
> If finalize chardev-msmouse or chardev-wctable is called immediately after
> init it cases QEMU to crash with segfault. This happens because of
> QTAILQ_REMOVE in qemu_input_handler_unregister tries to dereference
> NULL pointer.
> For instance, this error can be reproduced via `qom-list-properties`
> command.
> 
> Signed-off-by: Maksim Davydov<davydov-max@yandex-team.ru>


Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>

-- 
Best regards,
Vladimir

Hi


On Thu, Aug 25, 2022 at 9:02 PM Maksim Davydov <davydov-max@yandex-team.ru>
wrote:

> If finalize chardev-msmouse or chardev-wctable is called immediately after
> init it cases QEMU to crash with segfault. This happens because of
> QTAILQ_REMOVE in qemu_input_handler_unregister tries to dereference
> NULL pointer.
> For instance, this error can be reproduced via `qom-list-properties`
> command.
>
> Signed-off-by: Maksim Davydov <davydov-max@yandex-team.ru>
>

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>


> ---
>  chardev/msmouse.c  | 4 +++-
>  chardev/wctablet.c | 4 +++-
>  2 files changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/chardev/msmouse.c b/chardev/msmouse.c
> index eb9231dcdb..2cc1b16561 100644
> --- a/chardev/msmouse.c
> +++ b/chardev/msmouse.c
> @@ -146,7 +146,9 @@ static void char_msmouse_finalize(Object *obj)
>  {
>      MouseChardev *mouse = MOUSE_CHARDEV(obj);
>
> -    qemu_input_handler_unregister(mouse->hs);
> +    if (mouse->hs) {
> +        qemu_input_handler_unregister(mouse->hs);
> +    }
>  }
>
>  static QemuInputHandler msmouse_handler = {
> diff --git a/chardev/wctablet.c b/chardev/wctablet.c
> index e8b292c43c..43bdf6b608 100644
> --- a/chardev/wctablet.c
> +++ b/chardev/wctablet.c
> @@ -319,7 +319,9 @@ static void wctablet_chr_finalize(Object *obj)
>  {
>      TabletChardev *tablet = WCTABLET_CHARDEV(obj);
>
> -    qemu_input_handler_unregister(tablet->hs);
> +    if (tablet->hs) {
> +        qemu_input_handler_unregister(tablet->hs);
> +    }
>  }
>
>  static void wctablet_chr_open(Chardev *chr,
> --
> 2.25.1
>
>
>

-- 
Marc-André Lureau