CVE-2019-12155 QEMU: qxl: null pointer dereference while releasing spice resources

[P J P <ppandit () redhat com>]

  Hello,

A null pointer dereference issue was found the QXL VGA card emulator of QEMU. 
It could occur while releasing resources allocated for a SPICE server thread 
in interface_release_resources().

A guest user could use this flaw to crash the QEMU process resulting in DoS 
scenario.

Upstream patch:
---------------
  -> https://git.qemu.org/?p=qemu.git;a=commit;h=d52680fc932efb8a2f334cc6993e705ed1e31e99

This issue was reported by Sergej Schumilo, Cornelius Aschermann and Simon 
Wrner of Ruhr University Bochum.

Thank you.
--
Prasad J Pandit / Red Hat Product Security Team
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