Remove the extra copy of the GPL license and license copyright headers
from CONTRIBUTING and the top-level COPYING.
Mention of the LICENSES/ directory and also mention the SPDX tag.
SPDX support is still in progress and COPYING files in subdirectories
still need to be updated.
Signed-off-by: Stefano Stabellini <stefano.stabellini@amd.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Release-acked-by: Henry Wang <Henry.Wang@arm.com>
Add the individual licenses under a new top-level directory named
"LICENSES". Each license file includes its related SPDX tags.
Signed-off-by: Stefano Stabellini <stefano.stabellini@amd.com>
Acked-by: Julien Grall <jgrall@amazon.com>
Release-acked-by: Henry Wang <Henry.Wang@arm.com>
The commit 3c2a14ea81 is introducing some unsupported arm features
that by default are disabled and are used for the cpufeature.c code.
As they are disabled by default, a typo in the Kconfig symbol they
depend on has landed in the codebase unnoticed, instead of depending
on ARM64 which does not exist, fix the code to depend on ARM_64 that
is the intended symbol.
Fixes: 3c2a14ea81 ("arm: Define kconfig symbols used by arm64 cpufeatures")
Signed-off-by: Luca Fancellu <luca.fancellu@arm.com>
Release-acked-by: Henry Wang <Henry.Wang@arm.com>
Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>
This reverts a small part of 7e21b25059 ("xen: harmonize return types
of hypercall handlers"). The change from "unsigned long" to "unsigned
int" for the native handler function meant that previously invalid
values became valid. While perhaps not a significant issue, strictly
speaking that's still a change to the ABI. Don't go as far as restoring
the compat entry point's type though: That one can't have values passed
which don't fit in 32 bits.
Note that as a side effect this fixes the invocation of
hypercall_create_continuation(), which by mistake wasn't adjusted by the
earlier change.
Also take the opportunity and correct the respective comment in the
public header. (The way it was it really supports that it probably was
pointless to use "long", but that's the way the hypercall was
introduced.)
Requested-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
Release-acked-by: Henry Wang <Henry.Wang@arm.com>
This reverts commit adb715db69.
The dumping of stacks for HVM guests is problematic, since it requires
taking the p2m lock in order to walk the guest page tables and the p2m.
The suggested solution to the issue is to introduce and use a lockless p2m
walker, that relies on being executed with interrupts disabled in order to
prevent any p2m pages from being freed while doing the walk.
Note that modifications of p2m entries are already done atomically in order
to prevent the hardware walker from seeing partially updated values.
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
Release-acked-by: Henry Wang <Henry.Wang@arm.com>
Commit 1283af6465 ("tools/xenstore: remove XEN_LIB_STORED and
XENSTORED_ROOTDIR") removed the systemd file var-lib-xenstored.mount
without removing dependencies to this file.
Fixes: 1283af6465 ("tools/xenstore: remove XEN_LIB_STORED and XENSTORED_ROOTDIR")
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>
Release-acked-by: Henry Wang <Henry.Wang@arm.com>
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>
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>
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>
domain_build use ioremap_wc to map a new non-cacheable virtual
address for initrd. After Xen copy initrd from this address to
guest, this new allocated virtual address has not been unmapped.
So in this patch, we add an iounmap to the end of domain_build,
after Xen loaded initrd to guest memory.
Signed-off-by: Wei Chen <wei.chen@arm.com>
Release-acked-by: Henry Wang <Henry.Wang@arm.com>
Acked-by: Julien Grall <jgrall@amazon.com>
If a guest is running in 32 bit mode and it tries to access
"GICR_PENDBASER + 4" mmio reg, it will be trapped to Xen. vreg_reg64_extract()
will return the value stored "v->arch.vgic.rdist_pendbase + 4".
This will be stored in a 64bit cpu register.
So now we have the top 32 bits of GICR_PENDBASER (a 64 bit MMIO register) stored
in the lower 32 bits of the 64bit cpu register.
This 64bit cpu register is then modified bitwise with a mask (ie
GICR_PENDBASER_PTZ, it clears the 62nd bit). But the PTZ (which is bit 30 in the
64 bit cpu register) is not cleared as expected by the specification.
The correct thing to do here is to store the value of
"v->arch.vgic.rdist_pendbase" in a temporary 64 bit variable. This variable is
then modified bitwise with GICR_PENDBASER_PTZ mask. It is then passed to
vreg_reg64_extract() which will extract 32 bits from the given offset.
Also, we have removed spin_lock_irqsave()/spin_unlock_irqrestore() to protect
v->arch.vgic.rdist_pendbase in __vgic_v3_rdistr_rd_mmio_read(). The reason
being v->arch.vgic.rdist_pendbase is now being read in an atomic manner.
Similarly in __vgic_v3_rdistr_rd_mmio_write(), we have used read_atomic(),
write_atomic() to read/write v->arch.vgic.rdist_pendbase.
Fixes: fe7fa1332d ("ARM: vGICv3: handle virtual LPI pending and property tables")
Signed-off-by: Ayan Kumar Halder <ayankuma@amd.com>
Release-acked-by: Henry Wang <Henry.Wang@arm.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
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>
Release-acked-by: Henry Wang <Henry.Wang@arm.com>
The code generated for the call_handlers_*() macros needs to avoid
undefined behavior when multiple handlers share the same priority.
The issue is the hypercall number being unverified fed into the macros
and then used to set a mask via "mask = 1ULL << <hypercall-number>".
Avoid a shift amount of more than 63 by setting mask to zero in case
the hypercall number is too large.
Fixes: eca1f00d02 ("xen: generate hypercall interface related code")
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Release-acked-by: Henry Wang <Henry.Wang@arm.com>
Similar to the EHCI driver - save/restore relevant BAR and command
register, re-configure DbC on resume and stop/start timer.
On resume trigger sending anything that was queued in the meantime.
Save full BAR value, instead of just the address part, to ease restoring
on resume.
Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Release-acked-by: Henry Wang <Henry.Wang@arm.com>
Re-use rmrr= parameter handling code to handle common device reserved
memory.
Move MAX_USER_RMRR_PAGES limit enforcement to apply only to
user-configured ranges, but not those from internal callers.
Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Release-acked-by: Henry Wang <Henry.Wang@arm.com>
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>
Release-acked-by: Henry Wang <Henry.Wang@arm.com>
XEN_LIB_STORED is serving no real purpose, as it is a mount point for
a tmpfs, so it can be replaced easily by XEN_RUN_STORED.
XENSTORED_ROOTDIR is basically unused already, there is just a single
reference in xs_daemon_rootdir() with a fallback to XEN_LIB_STORED,
and a .gdbinit file setting it.
Remove the .gdbinit file, as it is not known having been used since
ages, and make xs_daemon_rootdir() an alias of xs_daemon_rundir().
Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
Release-acked-by: Henry Wang <Henry.Wang@arm.com>
Add MSR_VIRT_SPEC_CTRL to the list of MSRs handled by
hvm_load_cpu_msrs(), or else it would be lost.
Fixes: 8ffd5496f4 ('amd/msr: implement VIRT_SPEC_CTRL for HVM guests on top of SPEC_CTRL')
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Release-acked-by: Henry Wang <Henry.Wang@arm.com>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
Add the memory accounting for Xenstore nodes. In order to make this
not too complicated allow for some sloppiness when writing nodes. Any
hard quota violation will result in no further requests to be accepted.
This is part of XSA-326 / CVE-2022-42315.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Add the memory accounting for registered watches.
When a socket connection is destroyed, the associated watches are
removed, too. In order to keep memory accounting correct the watches
must be removed explicitly via a call of conn_delete_all_watches() from
destroy_conn().
This is part of XSA-326 / CVE-2022-42315.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Add the memory accounting for queued responses.
In case adding a watch event for a guest is causing the hard memory
quota of that guest to be violated, the event is dropped. This will
ensure that it is impossible to drive another guest past its memory
quota by generating insane amounts of events for that guest. This is
especially important for protecting driver domains from that attack
vector.
This is part of XSA-326 / CVE-2022-42315.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
The amount of memory a domain can consume in Xenstore is limited by
various quota today, but even with sane quota a domain can still
consume rather large memory quantities.
Add the infrastructure for keeping track of the amount of memory a
domain is consuming in Xenstore. Note that this is only the memory a
domain has direct control over, so any internal administration data
needed by Xenstore only is not being accounted for.
There are two quotas defined: a soft quota which will result in a
warning issued via syslog() when it is exceeded, and a hard quota
resulting in a stop of accepting further requests or watch events as
long as the hard quota would be violated by accepting those.
Setting any of those quotas to 0 will disable it.
As default values use 2MB per domain for the soft limit (this basically
covers the allowed case to create 1000 nodes needing 2kB each), and
2.5MB for the hard limit.
This is part of XSA-326.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Setting up the basic structure when introducing dom0 has the advantage
to be able to add proper node memory accounting for the added nodes
later.
This makes it possible to do proper node accounting, too.
An additional requirement to make that work fine is to correct the
owner of the created nodes to be dom0_domid instead of domid 0.
This is part of XSA-326.
Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Julien Grall <jgrall@amazon.com>
Today a guest is free to access as many nodes in a single transaction
as it wants. This can lead to unbounded memory consumption in Xenstore
as there is the need to keep track of all nodes having been accessed
during a transaction.
In oxenstored the number of requests in a transaction is being limited
via a quota maxrequests (default is 1024). As multiple accesses of a
node are not problematic in C Xenstore, limit the number of accessed
nodes.
In order to let read_node() detect a quota error in case too many nodes
are being accessed, check the return value of access_node() and return
NULL in case an error has been seen. Introduce __must_check and add it
to the access_node() prototype.
This is part of XSA-326 / CVE-2022-42314.
Suggested-by: Julien Grall <julien@xen.org>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
The accounting of nodes can be simplified now that each connection
holds the associated domid.
Fix the node accounting to cover nodes created for a domain before it
has been introduced. This requires to react properly to an allocation
failure inside domain_entry_inc() by returning an error code.
Especially in error paths the node accounting has to be fixed in some
cases.
This is part of XSA-326 / CVE-2022-42313.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Stefano Stabellini