domctl: perform initial post-XSA-77 auditing

domctl: perform initial post-XSA-77 auditing

In a number of cases, loops over each vCPU in a domain are involved
here. For large numbers of vCPU-s these may still take some time to
complete, but we're limiting them at a couple of thousand at most, so I
would think this should not by itself be an issue. I wonder though
whether it shouldn't be possible to have XSM restrict the vCPU count
that can be set through XEN_DOMCTL_max_vcpus.

XEN_DOMCTL_pausedomain:

 A loop over vcpu_sleep_sync() for each of vCPU in the domain. That
 function itself has a loop waiting for the subject vCPU to become non-
 runnable, which ought to complete quickly (involving an IPI to be sent
 and acted on). No other unbounded resource usage.

XEN_DOMCTL_unpausedomain:

 Simply a loop calling vcpu_wake() (not having any loops or other
 resource usage itself) for each of vCPU in the domain.

XEN_DOMCTL_getdomaininfo:

 Two loops (one over all domains, i.e. bounded by the limit of 32k
 domains, and another over all vCPU-s in the domain); no other
 unbounded resource usage.

XEN_DOMCTL_getpageframeinfo:

 Inquiring just a single MFN, i.e. no loops and no other unbounded
 resource usage.

XEN_DOMCTL_getpageframeinfo{2,3}:

 Number of inquired MFNs is limited to 1024. Beyond that just like
 XEN_DOMCTL_getpageframeinfo.

XEN_DOMCTL_getvcpuinfo:

 Only obtaining information on the vCPU, no loops or other resource
 usage.

XEN_DOMCTL_setdomainhandle:

 Simply a memcpy() of a very limited amount of data.

XEN_DOMCTL_setdebugging:

 A domain_{,un}pause() pair (see XEN_DOMCTL_{,un}pausedomain) framing
 the setting of a flag.

XEN_DOMCTL_hypercall_init:

 Initializing a guest provided page with hypercall stubs. No other
 resource consumption.

XEN_DOMCTL_arch_setup:

 IA64 leftover, interface structure being removed from the public
 header.

XEN_DOMCTL_settimeoffset:

 Setting a couple of guest state fields. No other resource consumption.

XEN_DOMCTL_getvcpuaffinity:
XEN_DOMCTL_getnodeaffinity:

 Involve temporary memory allocations (approximately) bounded by the
 number of CPUs in the system / number of nodes built for, which is
 okay. Beyond that trivial operation.

XEN_DOMCTL_real_mode_area:

 PPC leftover, interface structure being removed from the public
 header.

XEN_DOMCTL_resumedomain:

 A domain_{,un}pause() pair framing operation very similar to
 XEN_DOMCTL_unpausedomain (see above).

XEN_DOMCTL_sendtrigger:

 Injects an interrupt (SCI or NMI) without any other resource
 consumption.

XEN_DOMCTL_subscribe:

 Updates the suspend event channel, i.e. affecting only the controlled
 domain.

XEN_DOMCTL_disable_migrate:
XEN_DOMCTL_suppress_spurious_page_faults:

 Just setting respective flags on the domain.

XEN_DOMCTL_get_address_size:

 Simply reading the guest property.

XEN_DOMCTL_set_opt_feature:

 Was already tagged IA64-only.

XEN_DOMCTL_set_cpuid:

 MAX_CPUID_INPUT bounded loop, which is okay. No other resource
 consumption.

XEN_DOMCTL_get_machine_address_size:

 Simply obtaining the value set by XEN_DOMCTL_set_machine_address_size
 (or the default set at domain creation time).

XEN_DOMCTL_gettscinfo:
XEN_DOMCTL_settscinfo:

 Reading/writing of a couple of guest state fields wrapped in a
 domain_{,un}pause() pair.

XEN_DOMCTL_audit_p2m:

 Enabled only in debug builds.

XEN_DOMCTL_set_max_evtchn:

 While the limit set here implies other (subsequent) resource usage,
 this is the purpose of the operation.

I also verified that all removed domctls' handlers don't leak
hypervisor memory contents .

Inspected but questionable (and hence left in place for now):

XEN_DOMCTL_max_mem:

 While only setting the field capping a domain's allocation (this
 implies potential successive resource usage, but that's the purpose of
 the operation). However, XSM doesn't see the value that's being set
 here, so the net effect would be potential unbounded memory use.

XEN_DOMCTL_set_virq_handler:

 This modifies a global array. While that is the purpose of the
 operation, if multiple domains are granted permission they can badly
 interfere with one another. Hence I'd appreciate a second opinion
 here. [Andrew confirms that this being the nature of the operation,
 it's fine to be removed from the list - will be done in a 2nd round.]

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Tim Deegan <tim@xen.org>