This will make the logic clearer when we plumb local_port through these
functions.
While doing this, rearrange the construct in Domains.create0 to separate the
remote port handling from the interface handling. (The interface logic is
dubious in several ways, but not altered by this cleanup.)
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Edwin Török <edvin.torok@citrix.com>
Acked-by: Christian Lindig <christian.lindig@citrix.com>
(cherry picked from commit 31fbee749a)
Xenstored always needs to bind the DOM_EXC VIRQ.
Instead of doing it shortly after the call to Event.init(), do it in the
constructor directly. This removes the need for the field to be a mutable
option.
It will also simplify a future change to support live update. Rename the
field from virq_port (which could be any VIRQ) to it's proper name.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Edwin Török <edvin.torok@citrix.com>
Acked-by: Christian Lindig <christian.lindig@citrix.com>
(cherry picked from commit 9804a5db43)
This file has some style problems so severe that they interfere with the
readability of the subsequent bugfix patches.
Fix these issues ahead of time, to make the subsequent changes more readable.
No functional change.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Edwin Török <edvin.torok@citrix.com>
Acked-by: Christian Lindig <christian.lindig@citrix.com>
(cherry picked from commit b45bfaf359)
For live update, oxenstored wants to clear CLOEXEC on the evtchn handle, so it
survives the execve() into the new oxenstored.
Have the new interface match how cloexec works in other Ocaml standard
libraries.
Signed-off-by: Edwin Török <edvin.torok@citrix.com>
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Christian Lindig <christian.lindig@citrix.com>
(cherry picked from commit 9bafe4a533)
There is no binding for xenevtchn_close(). In principle, this is a resource
leak, but the typical usage is as a singleton that lives for the lifetime of
the program.
Ocaml 5 no longer permits storing a naked C pointer in an Ocaml value.
Therefore, use a Custom block. This allows us to use the finaliser callback
to call xenevtchn_close(), if the Ocaml object goes out of scope.
Signed-off-by: Edwin Török <edvin.torok@citrix.com>
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Christian Lindig <christian.lindig@citrix.com>
(cherry picked from commit 22d5affdf0)
A debug statement got inserted into a single-expression if statement.
Insert brackets to give the intended meaning, rather than the actual meaning
where the "let con = Connections..." is outside and executed unconditionally.
This results in some unnecessary ring checks for domains which otherwise have
IO credit.
Fixes: 42f0581a91 ("tools/oxenstored: Implement live update for socket connections")
Reported-by: Edwin Török <edvin.torok@citrix.com>
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Christian Lindig <christian.lindig@citrix.com>
(cherry picked from commit ee36179371)
Building with Dune in release mode fails with:
```
File "ocaml/xenstored/store.ml", line 464, characters 13-32:
Warning 18: this type-based record disambiguation is not principal.
File "ocaml/xenstored/store.ml", line 1:
Error: Some fatal warnings were triggered (1 occurrences)
```
This is a warning to help keep the code futureproof, quoting from its
documentation:
> Check information path during type-checking, to make sure that all types are
> derived in a principal way. When using labelled arguments and/or polymorphic
> methods, this flag is required to ensure future versions of the compiler will
> be able to infer types correctly, even if internal algorithms change. All
> programs accepted in -principal mode are also accepted in the default mode with
> equivalent types, but different binary signatures, and this may slow down type
> checking; yet it is a good idea to use it once before publishing source code.
Fixes: db471408ed "tools/ocaml/xenstored: Fix quota bypass on domain shutdown"
Signed-off-by: Edwin Török <edvin.torok@citrix.com>
Acked-by: Christian Lindig <christian.lindig@citrix.com>
Release-acked-by: Henry Wang <Henry.Wang@arm.com>
(cherry picked from commit 124492eff8)
During live update we will load the /tool/xenstored path from the previous binary,
and then try to mkdir /tool again which will fail with EEXIST.
Check for existence of the path before creating it.
The write call to /tool/xenstored should not need any changes
(and we do want to overwrite any previous path, in case it changed).
Prior to 7110192b1d live update would work only if the binary path was
specified, and with 7110192b1d and this live update also works when
no binary path is specified in `xenstore-control live-update`.
Fixes: 7110192b1d ("tools/oxenstored: Fix Oxenstored Live Update")
Signed-off-by: Edwin Török <edvin.torok@citrix.com>
Acked-by: Christian Lindig <christian.lindig@citrix.com>
Release-acked-by: Henry Wang <Henry.Wang@arm.com>
(cherry picked from commit f838b95677)
Linux'es relatively new use of HVMOP_set_evtchn_upcall_vector has
exposed a problem with the marking of the respective vector as
pending: For quite some time Linux has been checking whether any stale
ISR or IRR bits would still be set while preparing the LAPIC for use.
This check is now triggering on the upcall vector, as the registration,
at least for APs, happens before the LAPIC is actually enabled.
In software-disabled state an LAPIC would not accept any interrupt
requests and hence no IRR bit would newly become set while in this
state. As a result it is also wrong for us to mark the upcall vector as
having a pending request when the vLAPIC is in this state.
To compensate for the "enabled" check added to the assertion logic, add
logic to (conditionally) mark the upcall vector as having a request
pending at the time the LAPIC is being software-enabled by the guest.
Note however that, like for the pt_may_unmask_irq() we already have
there, long term we may need to find a different solution. This will be
especially relevant in case yet better LAPIC acceleration would
eliminate notifications of guest writes to this and other registers.
Fixes: 7b5b8ca7df ("x86/upcall: inject a spurious event after setting upcall vector")
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
master commit: f5d0279839
master date: 2022-12-06 13:51:49 +0100
In software-disabled state an LAPIC does not accept any interrupt
requests and hence no IRR bit would newly become set while in this
state. As a result it is also wrong for us to mark Viridian IPI or timer
vectors as having a pending request when the vLAPIC is in this state.
Such interrupts are simply lost.
Introduce a local variable in send_ipi() to help readability.
Fixes: fda96b7382 ("viridian: add implementation of the HvSendSyntheticClusterIpi hypercall")
Fixes: 26fba3c855 ("viridian: add implementation of synthetic timers")
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Paul Durrant <paul@xen.org>
master commit: 831419f829
master date: 2022-12-02 10:35:32 +0100
In software-disabled state an LAPIC does not accept any interrupt
requests and hence no IRR bit would newly become set while in this
state. As a result it is also wrong for us to mark IO-APIC or MSI
originating vectors as having a pending request when the vLAPIC is in
this state. Such interrupts are simply lost.
Introduce (IO-APIC) or re-use (MSI) a local variable to help
readability.
Fixes: 4fe21ad371 ("This patch add virtual IOAPIC support for VMX guest")
Fixes: 85715f4bc7 ("MSI 5/6: add MSI support to passthrough HVM domain")
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
master commit: f1d7aac1e3
master date: 2022-12-02 10:35:01 +0100
Currently Xen will passthrough any Local APIC NMI Structure found in
the native ACPI MADT table to a PVH dom0. This is wrong because PVH
doesn't have access to the physical local APIC, and instead gets an
emulated local APIC by Xen, that doesn't have the LINT0 or LINT1
pins wired to anything. Furthermore the ACPI Processor UIDs used in
the APIC NMI Structures are likely to not match the ones generated by
Xen for the Local x2APIC Structures, creating confusion to dom0.
Fix this by removing the logic to passthrough the Local APIC NMI
Structure for PVH dom0.
Fixes: 1d74282c45 ('x86: setup PVHv2 Dom0 ACPI tables')
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
master commit: b39e638525
master date: 2022-12-02 10:33:40 +0100
Current code in _clear_irq_vector() will mark the irq as unused before
doing the cleanup required when move_in_progress is true.
This can lead to races in create_irq() if the function picks an irq
desc that's been marked as unused but has move_in_progress set, as the
call to assign_irq_vector() in that function can then fail with
-EAGAIN.
Prevent that by only marking irq descs as unused when all the cleanup
has been done. While there also use write_atomic() when setting
IRQ_UNUSED in _clear_irq_vector() and add a barrier in order to
prevent the setting of IRQ_UNUSED getting reordered by the compiler.
The check for move_in_progress cannot be removed from
_assign_irq_vector(), as other users (io_apic_set_pci_routing() and
ioapic_guest_write()) can still pass active irq descs to
assign_irq_vector().
Note the trace point is not moved and is now set before the irq is
marked as unused. This is done so that the CPU mask provided in the
trace point is the one belonging to the current vector, not the old
one.
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
master commit: e267d11969
master date: 2022-12-02 10:32:21 +0100
Allocating or freeing p2m pages doesn't alter the size of the mempool; only
the split between free and used pages.
Right now, the hypercalls operate on the free subset of the pool, meaning that
XEN_DOMCTL_get_paging_mempool_size varies with time as the guest shuffles its
physmap, and XEN_DOMCTL_set_paging_mempool_size ignores the used subset of the
pool and lets the guest grow unbounded.
This fixes test-pagign-mempool on ARM so that the behaviour matches x86.
This is part of XSA-409 / CVE-2022-33747.
Fixes: cbea5a1149 ("xen/arm: Allocate and free P2M pages from the P2M pool")
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Release-acked-by: Henry Wang <Henry.Wang@arm.com>
Commit 34990446ca started to overwrite the `rc` value from
libxl__arch_domain_create(), thus error aren't propagated anymore.
Check `rc` value before doing the next thing.
Fixes: 34990446ca ("libxl: don't ignore the return value from xc_cpuid_apply_policy")
Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Reviewed-by: Jason Andryuk <jandryuk@gmail.com>
master commit: 8cdfbf95b1
master date: 2022-11-21 12:23:01 +0100
On one of my boxes when the HDMI cable is not plugged in the
FrameBufferBase of the EFI_GRAPHICS_OUTPUT_PROTOCOL_MODE structure is
set to 0 by the firmware (while some of the other fields looking
plausible).
Such (bogus address) ends up mapped in vesa_init(), and since it
overlaps with a RAM region the whole system goes down pretty badly,
see:
(XEN) vesafb: framebuffer at 0x0000000000000000, mapped to 0xffff82c000201000, using 35209k, total 35209k
(XEN) vesafb: mode is 0x37557x32, linelength=960, font 8x16
(XEN) vesafb: Truecolor: size=8:8:8:8, shift=24:0:8:16
(XEN) (XEN) (XEN) (XEN) (XEN) (XEN) (XEN) (XEN) �ERROR: Class:0; Subclass:0; Operation: 0
ERROR: No ConOut
ERROR: No ConIn
Do like Linux and prevent using the EFI Frame Buffer if the base
address is 0. This is inline with the logic in Linuxes
fb_base_is_valid() function at drivers/video/fbdev/efifb.c v6.0.9.
See also Linux commit 133bb070e94ab41d750c6f2160c8843e46f11b78 for
further reference.
Also prevent using Frame Buffers that have a 0 height or width, as
those are also invalid.
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
master commit: 57f07cca82
master date: 2022-11-21 12:21:51 +0100
... now that we a link available.
Fixes: 9deaf2d932 ("x86/spec-ctrl: Enable Zen2 chickenbit")
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
master commit: 764146ed8a
master date: 2022-11-16 12:54:08 +0000
Today all timers are migrated to cpu 0 when the system is being
suspended. They are not migrated back after resuming the system again.
This results (at least) to visible problems with the credit scheduler,
as the timer isn't handled on the cpu it was expected to occur, which
will result in an ASSERT() triggering. Other more subtle problems, like
uninterrupted elongated time slices, are probable. The least effect
will be worse performance on cpu 0 resulting from most scheduling
related timer interrupts happening there after suspend/resume.
Add migrating the scheduling related timers of a specific cpu from cpu
0 back to its original cpu when that cpu has gone up when resuming the
system.
Fixes: 0763cd2687 ("xen/sched: don't disable scheduler on cpus during suspend")
Signed-off-by: Juergen Gross <jgross@suse.com>
Tested-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Acked-by: Dario Faggioli <dfaggioli@suse.com>
master commit: 37f82facd6
master date: 2022-11-04 09:03:23 +0100
When destroying a domain, any stale permissions of the domain must be
removed from the special nodes "@...", too. This was not done in the
fix for XSA-322.
Fixes: 496306324d ("tools/xenstore: revoke access rights for removed domains")
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
master commit: 0751a75e39
master date: 2022-11-02 12:08:22 +0100
Introduce spec_ctrl_new_guest_context() to encapsulate all logic pertaining to
using MSR_PRED_CMD for a new guest context, even if it only has one user
presently.
Introduce X86_BUG_IBPB_NO_RET, and use it extend spec_ctrl_new_guest_context()
with a manual fixup for hardware which mis-implements IBPB.
This is part of XSA-422 / CVE-2022-23824.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
(cherry picked from commit 2b27967fb8)
The IBPB_RET bit indicates that the CPU's implementation of MSR_PRED_CMD.IBPB
does flush the RSB/RAS too.
This is part of XSA-422 / CVE-2022-23824.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
(cherry picked from commit 24496558e6)
When finalizing a transaction, any error occurring after checking for
conflicts will result in the transaction being performed only
partially today. Additionally accounting data will not be updated at
the end of the transaction, which might result in further problems
later.
Avoid those problems by multiple modifications:
- free any transaction specific nodes which don't need to be committed
as they haven't been written during the transaction as soon as their
generation count has been verified, this will reduce the risk of
out-of-memory situations
- store the transaction specific node name in struct accessed_node in
order to avoid the need to allocate additional memory for it when
finalizing the transaction
- don't stop the transaction finalization when hitting an error
condition, but try to continue to handle all modified nodes
- in case of a detected error do the accounting update as needed and
call the data base checking only after that
- if writing a node in a transaction is failing (e.g. due to a failed
quota check), fail the transaction, as prior changes to struct
accessed_node can't easily be undone in that case
This is part of XSA-421 / CVE-2022-42326.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Tested-by: Julien Grall <jgrall@amazon.com>
(cherry picked from commit 2dd823ca72)
In case a node has been created in a transaction and it is later
deleted in the same transaction, the transaction will be terminated
with an error.
As this error is encountered only when handling the deleted node at
transaction finalization, the transaction will have been performed
partially and without updating the accounting information. This will
enable a malicious guest to create arbitrary number of nodes.
This is part of XSA-421 / CVE-2022-42325.
Signed-off-by: Juergen Gross <jgross@suse.com>
Tested-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
(cherry picked from commit 13ac37f141)
Integers in Ocaml have 63 or 31 bits of signed precision.
On 64-bit builds of Ocaml, this is fine because a C uint32_t always fits
within a 63-bit signed integer.
In 32-bit builds of Ocaml, this goes wrong. The C uint32_t is truncated
first (loses the top bit), then has a unsigned/signed mismatch.
A "negative" value (i.e. a packet on the ring of between 1G and 2G in size)
will trigger an exception later in Bytes.make in xb.ml, and because the packet
is not removed from the ring, the exception re-triggers on every subsequent
query, creating a livelock.
Fix both the source of the exception in Xb, and as defence in depth, mark the
domain as bad for any Invalid_argument exceptions to avoid the risk of
livelock.
This is XSA-420 / CVE-2022-42324.
Signed-off-by: Edwin Török <edvin.torok@citrix.com>
Acked-by: Christian Lindig <christian.lindig@citrix.com>
(cherry picked from commit ae34df4d82)
XSA-322 fixed a domid reuse vulnerability by assigning Dom0 as the owner of
any nodes left after a domain is shutdown (e.g. outside its /local/domain/N
tree).
However Dom0 has no quota on purpose, so this opened up another potential
attack vector. Avoid it by deleting these nodes instead of assigning them to
Dom0.
This is part of XSA-419 / CVE-2022-42323.
Fixes: c46eff9212 ("tools/ocaml/xenstored: clean up permissions for dead domains")
Signed-off-by: Edwin Török <edvin.torok@citrix.com>
Acked-by: Christian Lindig <christian.lindig@citrix.com>
(cherry picked from commit db471408ed)
The permission scheme of Xenstore nodes is not really covered by
docs/misc/xenstore.txt, other than referring to the Xen wiki.
Add a paragraph explaining the permissions of nodes, and especially
mentioning removal of nodes when a domain has been removed from
Xenstore.
This is part of XSA-419.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Edwin Török <edvin.torok@citrix.com>
Acked-by: Julien Grall <jgrall@amazon.com>
(cherry picked from commit d084d2c6df)
Having a file backed data base has the only advantage of being capable
to dump the contents of it while Xenstore is running, and potentially
using less swap space in case the data base can't be kept in memory.
It has the major disadvantage of a huge performance overhead: switching
to keep the data base in memory only speeds up live update of xenstored
with 120000 nodes from 20 minutes to 11 seconds. A complete tree walk
of this configuration will be reduced from 7 seconds to 280 msecs
(measured by "xenstore-control check").
So make the internal memory data base the default and enhance the
"--internal-db" command line parameter to take an optional parameter
allowing to switch the internal data base back to the file based one.
This is part of XSA-419.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
(cherry picked from commit d174fefa90)
In case a domain is removed from Xenstore, remove all nodes owned by
it per default.
This tackles the problem that nodes might be created by a domain
outside its home path in Xenstore, leading to Xenstore hogging more
and more memory. Domain quota don't work in this case if the guest is
rebooting in between.
Since XSA-322 ownership of such stale nodes is transferred to dom0,
which is helping against unintended access, but not against OOM of
Xenstore.
As a fallback for weird cases add a Xenstore start parameter for
keeping today's way to handle stale nodes, adding the risk of Xenstore
hitting an OOM situation.
This is part of XSA-419 / CVE-2022-42322.
Fixes: 496306324d ("tools/xenstore: revoke access rights for removed domains")
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
(cherry picked from commit 755d3f9deb)
Instead of doing an open tree walk using call recursion, use
walk_node_tree() when creating the node records during a live update.
This will reduce code size and avoid many nesting levels of function
calls which could potentially exhaust the stack.
This is part of XSA-418 / CVE-2022-42321.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
(cherry picked from commit 297ac246a5)
Instead of doing an open tree walk using call recursion, use
walk_node_tree() when deleting a sub-tree of nodes.
This will reduce code size and avoid many nesting levels of function
calls which could potentially exhaust the stack.
This is part of XSA-418 / CVE-2022-42321.
Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Julien Grall <jgrall@amazon.com>
(cherry picked from commit ea16962053)
Instead of doing an open tree walk using call recursion, use
walk_node_tree() when checking the store for inconsistencies.
This will reduce code size and avoid many nesting levels of function
calls which could potentially exhaust the stack.
This is part of XSA-418 / CVE-2022-42321.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
(cherry picked from commit a07cc0ec60)
check_store() is using a hash table for storing all node names it has
found via walking the tree. Additionally it using another hash table
for all children of a node to detect duplicate child names.
Simplify that by dropping the second hash table as the first one is
already holding all the needed information.
This is part of XSA-418 / CVE-2022-42321.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
(cherry picked from commit 70f719f52a)
Add a generic function to walk the complete node tree. It will start
at "/" and descend recursively into each child, calling a function
specified by the caller. Depending on the return value of the user
specified function the walk will be aborted, continued, or the current
child will be skipped by not descending into its children.
This is part of XSA-418 / CVE-2022-42321.
Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Julien Grall <jgrall@amazon.com>
(cherry picked from commit 0d7c5d19bc)
In case of write_node() returning an error, remove_child_entry() will
call corrupt() today. This could result in an endless recursion, as
remove_child_entry() is called by corrupt(), too:
corrupt()
check_store()
check_store_()
remove_child_entry()
Fix that by letting remove_child_entry() return an error instead and
let the caller decide what to do.
This is part of XSA-418 / CVE-2022-42321.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
(cherry picked from commit 0c00c51f3b)
In order to reduce stack usage due to recursion, switch
construct_node() to use a loop instead.
This is part of XSA-418 / CVE-2022-42321.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
(cherry picked from commit da8ee25d02)
Today chk_domain_generation() is being used to check whether a node
permission entry is still valid or whether it is referring to a domain
no longer existing. This is done by comparing the node's and the
domain's generation count.
In case no struct domain is existing for a checked domain, but the
domain itself is valid, chk_domain_generation() assumes it is being
called due to the first node created for a new domain and it will
return success.
This might be wrong in case the checked permission is related to an
old domain, which has just been replaced with a new domain using the
same domid.
Fix that by letting chk_domain_generation() fail in case a struct
domain isn't found. In order to cover the case of the first node for
a new domain try to allocate the needed struct domain explicitly when
processing the related SET_PERMS command. In case a referenced domain
isn't existing, flag the related permission to be ignored right away.
This is XSA-417 / CVE-2022-42320.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
(cherry picked from commit ab12821822)
Using the struct buffered data pointer of the current processed request
for temporary data allocations has a major drawback: the used area (and
with that the temporary data) is freed only after the response of the
request has been written to the ring page or has been read via the
socket. This can happen much later in case a guest isn't reading its
responses fast enough.
As the temporary data can be safely freed after creating the response,
add a temporary context for that purpose and use that for allocating
the temporary memory, as it was already the case before commit
cc06124648 ("xenstore: add small default data buffer to internal
struct").
Some sub-functions need to gain the "const" attribute for the talloc
context.
This is XSA-416 / CVE-2022-42319.
Fixes: cc06124648 ("xenstore: add small default data buffer to internal struct")
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
(cherry picked from commit 2a587de219)
Add a support statement for the scope of support regarding different
Xenstore variants. Especially oxenstored does not (yet) have security
support of untrusted driver domains, as those might drive oxenstored
out of memory by creating lots of watch events for the guests they are
servicing.
Add a statement regarding Live Update support of oxenstored.
This is part of XSA-326.
Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: George Dunlap <george.dunlap@citrix.com>
Acked-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Christian Lindig <christian.lindig@citrix.com>
(cherry picked from commit c7bc20d8d1)
Introduce a limit on the number of outstanding reply packets in the xenbus
queue. This limits the number of in-flight requests: when the output queue is
full we'll stop processing inputs until the output queue has room again.
To avoid a busy loop on the Unix socket we only add it to the watched input
file descriptor set if we'd be able to call `input` on it. Even though Dom0
is trusted and exempt from quotas a flood of events might cause a backlog
where events are produced faster than daemons in Dom0 can consume them, which
could lead to an unbounded queue size and OOM.
Therefore the xenbus queue limit must apply to all connections, Dom0 is not
exempt from it, although if everything works correctly it will eventually
catch up.
This prevents a malicious guest from sending more commands while it has
outstanding watch events or command replies in its input ring. However if it
can cause the generation of watch events by other means (e.g. by Dom0, or
another cooperative guest) and stop reading its own ring then watch events
would've queued up without limit.
The xenstore protocol doesn't have a back-pressure mechanism, and doesn't
allow dropping watch events. In fact, dropping watch events is known to break
some pieces of normal functionality. This leaves little choice to safely
implement the xenstore protocol without exposing the xenstore daemon to
out-of-memory attacks.
Implement the fix as pipes with bounded buffers:
* Use a bounded buffer for watch events
* The watch structure will have a bounded receiving pipe of watch events
* The source will have an "overflow" pipe of pending watch events it couldn't
deliver
Items are queued up on one end and are sent as far along the pipe as possible:
source domain -> watch -> xenbus of target -> xenstore ring/socket of target
If the pipe is "full" at any point then back-pressure is applied and we prevent
more items from being queued up. For the source domain this means that we'll
stop accepting new commands as long as its pipe buffer is not empty.
Before we try to enqueue an item we first check whether it is possible to send
it further down the pipe, by attempting to recursively flush the pipes. This
ensures that we retain the order of events as much as possible.
We might break causality of watch events if the target domain's queue is full
and we need to start using the watch's queue. This is a breaking change in
the xenstore protocol, but only for domains which are not processing their
incoming ring as expected.
When a watch is deleted its entire pending queue is dropped (no code is needed
for that, because it is part of the 'watch' type).
There is a cache of watches that have pending events that we attempt to flush
at every cycle if possible.
Introduce 3 limits here:
* quota-maxwatchevents on watch event destination: when this is hit the
source will not be allowed to queue up more watch events.
* quota-maxoustanding which is the number of responses not read from the ring:
once exceeded, no more inputs are processed until all outstanding replies
are consumed by the client.
* overflow queue on the watch event source: all watches that cannot be stored
on destination are queued up here, a single command can trigger multiple
watches (e.g. due to recursion).
The overflow queue currently doesn't have an upper bound, it is difficult to
accurately calculate one as it depends on whether you are Dom0 and how many
watches each path has registered and how many watch events you can trigger
with a single command (e.g. a commit). However these events were already
using memory, this just moves them elsewhere, and as long as we correctly
block a domain it shouldn't result in unbounded memory usage.
Note that Dom0 is not excluded from these checks, it is important that Dom0 is
especially not excluded when it is the source, since there are many ways in
which a guest could trigger Dom0 to send it watch events.
This should protect against malicious frontends as long as the backend follows
the PV xenstore protocol and only exposes paths needed by the frontend, and
changes those paths at most once as a reaction to guest events, or protocol
state.
The queue limits are per watch, and per domain-pair, so even if one
communication channel would be "blocked", others would keep working, and the
domain itself won't get blocked as long as it doesn't overflow the queue of
watch events.
Similarly a malicious backend could cause the frontend to get blocked, but
this watch queue protects the frontend as well as long as it follows the PV
protocol. (Although note that protection against malicious backends is only a
best effort at the moment)
This is part of XSA-326 / CVE-2022-42318.
Signed-off-by: Edwin Török <edvin.torok@citrix.com>
Acked-by: Christian Lindig <christian.lindig@citrix.com>
(cherry picked from commit 9284ae0c40)
Ensures we cannot store more than [capacity] elements in a [Queue]. Replacing
all Queue with this module will then ensure at compile time that all Queues
are correctly bound checked.
Each element in the queue has a class with its own limits. This, in a
subsequent change, will ensure that command responses can proceed during a
flood of watch events.
No functional change.
This is part of XSA-326.
Signed-off-by: Edwin Török <edvin.torok@citrix.com>
Acked-by: Christian Lindig <christian.lindig@citrix.com>
(cherry picked from commit 19171fb5d8)
The queue here would only ever hold at most one element. This will simplify
follow-up patches.
This is part of XSA-326.
Signed-off-by: Edwin Török <edvin.torok@citrix.com>
Acked-by: Christian Lindig <christian.lindig@citrix.com>
(cherry picked from commit c0a86a4627)
Hiding the type will make it easier to change the implementation
in the future without breaking code that relies on it.
No functional change.
Signed-off-by: Edwin Török <edvin.torok@citrix.com>
Acked-by: Christian Lindig <christian.lindig@citrix.com>
(cherry picked from commit 7ade30a145)
By default the OCaml garbage collector would return memory to the OS only
after unused memory is 5x live memory. Tweak this to 120% instead, which
would match the major GC speed.
This is part of XSA-326.
Signed-off-by: Edwin Török <edvin.torok@citrix.com>
Acked-by: Christian Lindig <christian.lindig@citrix.com>
(cherry picked from commit 4a8bacff20)
Previously we'd perform the operation, record the updated tree in the
transaction record, then try to insert a watchop path and the reply packet.
If we exceeded max requests we would've returned EQUOTA, but still:
* have performed the operation on the transaction's tree
* have recorded the watchop, making this queue effectively unbounded
It is better if we check whether we'd have room to store the operation before
performing the transaction, and raise EQUOTA there. Then the transaction
record won't grow.
This is part of XSA-326 / CVE-2022-42317.
Signed-off-by: Edwin Török <edvin.torok@citrix.com>
Acked-by: Christian Lindig <christian.lindig@citrix.com>
(cherry picked from commit 329f4d1a65)
We currently have 2 different set of defaults in upstream Xen git tree:
* defined in the source code, only used if there is no config file
* defined in the oxenstored.conf.in upstream Xen
An oxenstored.conf file is not mandatory, and if missing, maxrequests in
particular has an unsafe default.
Resync the defaults from oxenstored.conf.in into the source code.
This is part of XSA-326 / CVE-2022-42316.
Signed-off-by: Edwin Török <edvin.torok@citrix.com>
Acked-by: Christian Lindig <christian.lindig@citrix.com>
(cherry picked from commit 84734955d4)
Add a xenstore-control command "quota" to:
- show current quota settings
- change quota settings
- show current quota related values of a domain
Note that in the case the new quota is lower than existing one,
Xenstored may continue to handle requests from a domain exceeding the
new limit (depends on which one has been broken) and the amount of
resource used will not change. However the domain will not be able to
create more resource (associated to the quota) until it is back to below
the limit.
This is part of XSA-326.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
(cherry picked from commit 9c484bef83)
Some quota variables are not exported via header files.
This is part of XSA-326.
Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Julien Grall <jgrall@amazon.com>
(cherry picked from commit 1da16d5990)
Andrew Cooper
Edwin Török
Jan Beulich
Roger Pau Monné
Anthony PERARD
Henry Wang
Juergen Gross