Bug#946942: virglrenderer: CVE-2019-18389: heap buffer overflow in the vrend_renderer_transfer_write_iov function

[Salvatore Bonaccorso]

Control: retitle -1 virglrenderer: CVE-2019-18389 CVE-2019-18391

And from the same upstream merge request a second CVE assignment as
well for 

https://bugzilla.redhat.com/show_bug.cgi?id=1765589
https://gitlab.freedesktop.org/virgl/virglrenderer/merge_requests/314/diffs?commit_id=8c9cfb4e425542e96f0717189fe4658555baaf08
https://gitlab.freedesktop.org/virgl/virglrenderer/commit/2abeb1802e3c005b17a7123e382171b3fb665971

Regards,
Salvatore