Security update for xen

Open Source Vulnerabilities SUSE-SU-2017:2339-1

This update for xen fixes the following issues: - CVE-2017-12855: Premature clearing of GTF_writing / GTF_reading lead to potentially leaking sensitive information (XSA-230, bsc#1052686). - CVE-2017-12135: Unbounded recursion in grant table code allowed a malicious guest to crash the host or potentially escalate privileges/leak information (XSA-226, bsc#1051787). - CVE-2017-12137: Incorrectly-aligned updates to pagetables allowed for privilege escalation (XSA-227, bsc#1051788). - CVE-2017-11334: The address_space_write_continue function in exec.c allowed local guest OS privileged users to cause a denial of service (out-of-bounds access and guest instance crash) by leveraging use of qemu_map_ram_ptr to access guest ram block area (bsc#1048920). - CVE-2017-11434: The dhcp_decode function in slirp/bootp.c allowed local guest OS users to cause a denial of service (out-of-bounds read) via a crafted DHCP options string (bsc#1049578). - CVE-2017-10664: qemu-nbd did not ignore SIGPIPE, which allowed remote attackers to cause a denial of service (daemon crash) by disconnecting during a server-to-client reply attempt (bsc#1046637).