Re: [Qemu-devel] [PATCH] vnc: clear vs->tlscreds after unparenting it

["Daniel P. Berrange" <berrange@redhat.com>]

On Tue, Jan 12, 2016 at 01:52:39PM +0100, Wolfgang Bumiller wrote:
> This pointer should be cleared in vnc_display_close()
> otherwise a use-after-free can happen when when using the
> old style 'x509' and 'tls' options rather than a persistent
> tls-creds -object, by issuing monitor commands to change
> the vnc server like so:
> 
> Start with: -vnc unix:test.socket,x509,tls
> Then use the following monitor command:
>   change vnc unix:test.socket
> 
> After this the pointer is still set but invalid and a crash
> can be triggered for instance by issuing the same command a
> second time which will try to object_unparent() the same
> pointer again.
> ---
>  ui/vnc.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/ui/vnc.c b/ui/vnc.c
> index 09756cd..35843b5 100644
> --- a/ui/vnc.c
> +++ b/ui/vnc.c
> @@ -3134,6 +3134,7 @@ static void vnc_display_close(VncDisplay *vs)
>      vs->subauth = VNC_AUTH_INVALID;
>      if (vs->tlscreds) {
>          object_unparent(OBJECT(vs->tlscreds));
> +        vs->tlscreds = NULL;
>      }
>      g_free(vs->tlsaclname);
>      vs->tlsaclname = NULL;

Reviewed-by: Daniel P. Berrange <berrange@redhat.com>


Regards,
Daniel
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