Re: [Qemu-devel] [PATCH] vnc: fix segfault in closed connection handling

[Marc-André Lureau]

Hi

On Wed, Jan 31, 2018 at 2:06 PM, Klim Kireev <address@hidden> wrote:
> On one of our client's node, due to trying to read from closed ioc,
> a segmentation fault occured. Corresponding backtrace:
>

Oops, you probably forgot an extra space before the # interpreted as comment.

Do you have a reproducer?

> Having analyzed the coredump, I understood that the reason is that
> ioc_tag is reset on vnc_disconnect_start and ioc is cleaned
> in vnc_disconnect_finish. Between these two events due to some
> reasons the ioc_tag was set again and after vnc_disconnect_finish
> the handler is running with freed ioc,
> which led to the segmentation fault.
>
> I suggest to check ioc_tag in vnc_disconnect_finish to prevent such
> an occurrence.


>
> Signed-off-by: Klim Kireev <address@hidden>
> ---
>  ui/vnc.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/ui/vnc.c b/ui/vnc.c
> index 33b087221f..b8bf0180cb 100644
> --- a/ui/vnc.c
> +++ b/ui/vnc.c
> @@ -1270,6 +1270,10 @@ void vnc_disconnect_finish(VncState *vs)
>      }
>      g_free(vs->lossy_rect);
>
> +    if (vs->ioc_tag) {
> +        g_source_remove(vs->ioc_tag);
> +        vs->ioc_tag = 0;
> +    }
>      object_unref(OBJECT(vs->ioc));
>      vs->ioc = NULL;
>      object_unref(OBJECT(vs->sioc));
> --
> 2.14.3
>
>



-- 
Marc-André Lureau