xen: patch for XSAs: 197, 199, 207, 208, 209

XSA-197 Issue Description:

> The compiler can emit optimizations in qemu which can lead to double
> fetch vulnerabilities.  Specifically data on the rings shared
> between qemu and the hypervisor (which the guest under control can
> obtain mappings of) can be fetched twice (during which time the
> guest can alter the contents) possibly leading to arbitrary code
> execution in qemu.

More: https://xenbits.xen.org/xsa/advisory-197.html

XSA-199 Issue Description:

> The code in qemu which implements ioport read/write looks up the
> specified ioport address in a dispatch table.  The argument to the
> dispatch function is a uint32_t, and is used without a range check,
> even though the table has entries for only 2^16 ioports.
>
> When qemu is used as a standalone emulator, ioport accesses are
> generated only from cpu instructions emulated by qemu, and are
> therefore necessarily 16-bit, so there is no vulnerability.
>
> When qemu is used as a device model within Xen, io requests are
> generated by the hypervisor and read by qemu from a shared ring.  The
> entries in this ring use a common structure, including a 64-bit
> address field, for various accesses, including ioport addresses.
>
> Xen will write only 16-bit address ioport accesses.  However,
> depending on the Xen and qemu version, the ring may be writeable by
> the guest.  If so, the guest can generate out-of-range ioport
> accesses, resulting in wild pointer accesses within qemu.

More: https://xenbits.xen.org/xsa/advisory-199.html

XSA-207 Issue Description:

> Certain internal state is set up, during domain construction, in
> preparation for possible pass-through device assignment.  On ARM and
> AMD V-i hardware this setup includes memory allocation.  On guest
> teardown, cleanup was erroneously only performed when the guest
> actually had a pass-through device assigned.

More: https://xenbits.xen.org/xsa/advisory-207.html

XSA-209 Issue Description:

> When doing bitblt copy backwards, qemu should negate the blit width.
> This avoids an oob access before the start of video memory.

More: https://xenbits.xen.org/xsa/advisory-208.html

XSA-208 Issue Description:

> In CIRRUS_BLTMODE_MEMSYSSRC mode the bitblit copy routine
> cirrus_bitblt_cputovideo fails to check wethehr the specified memory
> region is safe.

More: https://xenbits.xen.org/xsa/advisory-209.html