The parameters of hashfn/eqfn should never be modified. So constify
them and propagate the const to the users.
Take the opportunity to solve some coding style issues around the
code modified.
Signed-off-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Henry Wang <Henry.Wang@arm.com>
Tested-by: Henry Wang <Henry.Wang@arm.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
I'm observing guest kexec trigger xenstored to abort on a double free.
gdb output:
Program received signal SIGABRT, Aborted.
__pthread_kill_implementation (no_tid=0, signo=6, threadid=140645614258112) at ./nptl/pthread_kill.c:44
44 ./nptl/pthread_kill.c: No such file or directory.
(gdb) bt
at ./nptl/pthread_kill.c:44
at ./nptl/pthread_kill.c:78
at ./nptl/pthread_kill.c:89
at ../sysdeps/posix/raise.c:26
at talloc.c:119
ptr=ptr@entry=0x559fae724290) at talloc.c:232
at xenstored_core.c:2945
(gdb) frame 5
at talloc.c:119
119 TALLOC_ABORT("Bad talloc magic value - double free");
(gdb) frame 7
at xenstored_core.c:2945
2945 talloc_increase_ref_count(conn);
(gdb) p conn
$1 = (struct connection *) 0x559fae724290
Looking at a xenstore trace, we have:
IN 0x559fae71f250 20230120 17:40:53 READ (/local/domain/3/image/device-model-dom
id )
wrl: dom 0 1 msec 10000 credit 1000000 reserve 100 disc
ard
wrl: dom 3 1 msec 10000 credit 1000000 reserve 100 disc
ard
wrl: dom 0 0 msec 10000 credit 1000000 reserve 0 disc
ard
wrl: dom 3 0 msec 10000 credit 1000000 reserve 0 disc
ard
OUT 0x559fae71f250 20230120 17:40:53 ERROR (ENOENT )
wrl: dom 0 1 msec 10000 credit 1000000 reserve 100 disc
ard
wrl: dom 3 1 msec 10000 credit 1000000 reserve 100 disc
ard
IN 0x559fae71f250 20230120 17:40:53 RELEASE (3 )
DESTROY watch 0x559fae73f630
DESTROY watch 0x559fae75ddf0
DESTROY watch 0x559fae75ec30
DESTROY watch 0x559fae75ea60
DESTROY watch 0x559fae732c00
DESTROY watch 0x559fae72cea0
DESTROY watch 0x559fae728fc0
DESTROY watch 0x559fae729570
DESTROY connection 0x559fae724290
orphaned node /local/domain/3/device/suspend/event-channel deleted
orphaned node /local/domain/3/device/vbd/51712 deleted
orphaned node /local/domain/3/device/vkbd/0 deleted
orphaned node /local/domain/3/device/vif/0 deleted
orphaned node /local/domain/3/control/shutdown deleted
orphaned node /local/domain/3/control/feature-poweroff deleted
orphaned node /local/domain/3/control/feature-reboot deleted
orphaned node /local/domain/3/control/feature-suspend deleted
orphaned node /local/domain/3/control/feature-s3 deleted
orphaned node /local/domain/3/control/feature-s4 deleted
orphaned node /local/domain/3/control/sysrq deleted
orphaned node /local/domain/3/data deleted
orphaned node /local/domain/3/drivers deleted
orphaned node /local/domain/3/feature deleted
orphaned node /local/domain/3/attr deleted
orphaned node /local/domain/3/error deleted
orphaned node /local/domain/3/console/backend-id deleted
and no further output.
The trace shows that DESTROY was called for connection 0x559fae724290,
but that is the same pointer (conn) main() was looping through from
connections. So it wasn't actually removed from the connections list?
Reverting commit e8e6e42279 "tools/xenstore: simplify loop handling
connection I/O" fixes the abort/double free. I think the use of
list_for_each_entry_safe is incorrect. list_for_each_entry_safe makes
traversal safe for deleting the current iterator, but RELEASE/do_release
will delete some other entry in the connections list. I think the
observed abort is because list_for_each_entry has next pointing to the
deleted connection, and it is used in the subsequent iteration.
Add a comment explaining the unsuitability of list_for_each_entry_safe.
Also notice that the old code takes a reference on next which would
prevents a use-after-free.
This reverts commit e8e6e42279.
This is XSA-425/CVE-2022-42330.
Fixes: e8e6e42279 ("tools/xenstore: simplify loop handling connection I/O")
Signed-off-by: Jason Andryuk <jandryuk@gmail.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Using a tab for separating the command from the options in the output
of "xenstore-control help" results in a rather ugly list.
Use a fixed size for the command instead.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Today check_store() is only testing the correctness of the node tree.
Add verification of the accounting data (number of nodes) and correct
the data if it is wrong.
Do the initial check_store() call only after Xenstore entries of a
live update have been read. This is wanted to make sure the accounting
data is correct after a live update.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Make the xenstored internal trace configurable by adding classes
which can be switched on and off independently from each other.
Define the following classes:
- obj: Creation and deletion of interesting "objects" (watch,
transaction, connection)
- io: incoming requests and outgoing responses
- wrl: write limiting
Per default "obj" and "io" are switched on.
Entries written via trace() will always be printed (if tracing is on
at all).
Add the capability to control the trace settings via the "log"
command and via a new "--log-control" command line option.
Add a missing trace_create() call for creating a transaction.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Instead of using malloc() and friends, let the hashtable implementation
use the talloc framework.
This is more consistent with the rest of xenstored and it allows to
track memory usage via "xenstore-control memreport".
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Letting hashtable_remove() return the value of the removed element is
not used anywhere in Xenstore, and it conflicts with a hashtable
created specifying the HASHTABLE_FREE_VALUE flag.
So just drop returning the value.
This of course requires to free the value if the HASHTABLE_FREE_VALUE
was specified, as otherwise it would be a memory leak.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Instead of returning 0 or 1 let chk_domain_generation() return a
boolean value.
Simplify the only caller by removing the ret variable.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
clang 14 is complaining about a NULL dereference for constructs like:
domain_is_unprivileged(conn) ? conn->in : NULL
as it can't know that domain_is_unprivileged(conn) will return false
if conn is NULL.
Fix that by making domain_is_unprivileged() an inline function (and
related to that domid_is_unprivileged(), too).
In order not having to make struct domain public, use conn->id instead
of conn->domain->domid for the test.
Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Julien Grall <jgrall@amazon.com>
There are some places left where dom0 is associated with domid 0.
Use dom0_domid instead.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Rework the interface and the internals of the per-domain node
accounting:
- rename the functions to domain_nbentry_*() in order to better match
the related counter name
- switch from node pointer to domid as interface, as all nodes have the
owner filled in
- use a common internal function for adding a value to the counter
For the transaction case add a helper function to get the list head
of the per-transaction changed domains, enabling to eliminate the
transaction_entry_*() functions.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Move all code related to struct changed_domain from
xenstored_transaction.c to xenstored_domain.c.
This will be needed later in order to simplify the accounting data
updates in cases of errors during a request.
Split the code to have a more generic base framework.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Instead of storing a pointer to the path which is prepended to
relative paths in struct watch, just use the length of the prepended
path.
It should be noted that the now removed special case of the
relative path being "" in get_watch_path() can't happen at all.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Instead of special casing the permission handling and watch event
firing for the special watch paths "@introduceDomain" and
"@releaseDomain", use static dummy nodes added to the data base when
starting Xenstore.
The node accounting needs to reflect that change by adding the special
nodes in the domain_entry_fix() call in setup_structure().
Note that this requires to rework the calls of fire_watches() for the
special events in order to avoid leaking memory.
Move the check for a valid node name from get_node() to
get_node_canonicalized(), as it allows to use get_node() for the
special nodes, too.
In order to avoid read and write accesses to the special nodes use a
special variant for obtaining the current node data for the permission
handling.
This allows to simplify quite some code. In future sub-nodes of the
special nodes will be possible due to this change, allowing more fine
grained permission control of special events for specific domains.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Move the definition of the log() macro to xenstored_core.h in order
to make it usable from other source files, too.
While at it preserve errno from being modified.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Today finding a struct domain by its domain id requires to scan the
list of domains until finding the correct domid.
Add a hashlist for being able to speed this up. This allows to remove
the linking of struct domain in a list. Note that the list of changed
domains per transaction is kept as a list, as there are no known use
cases with more than 4 domains being touched in a single transaction
(this would be a device handled by a driver domain and being assigned
to a HVM domain with device model in a stubdom, plus the control
domain).
Some simple performance tests comparing the scanning and hashlist have
shown that the hashlist will win as soon as more than 6 entries need
to be scanned.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
When a domain has been released by Xen tools, remove all its
registered watches. This avoids sending watch events to the dead domain
when all the nodes related to it are being removed by the Xen tools.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Today talloc_free() is not guaranteed to preserve errno, especially in
case a custom destructor is being used.
So preserve errno in talloc_free().
This allows to remove some errno saving outside of talloc.c.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Today it is possible to set a flag when calling hashtable_destroy() in
order to specify whether the data associated with the hashtable entries
should be freed or not. The keys of the entries will always be freed.
Change that by replacing the flag of hashtable_destroy() by two flags
for create_hashtable() which will specify whether the data and/or the
key of each entry should be freed or not.
This will enable users to have the key e.g. as part of the data.
Add a new function hashtable_iterate() to call a user specified
function for each entry in the hashtable.
Add new primes to the primetable in order to support smaller sizes of
the hashtable. The primes are selected according to:
https://planetmath.org/goodhashtableprimes
Update the URL in the source as the old one wasn't correct any longer.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Let corrupt() preserve errno in order to be able to simplify error
handling in future.
This is rather easy as the errno value when entering corrupt() is
saved already.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
tdb_logger() is called by TDB for logging errors. As errno is checked
often after doing the logging, tdb_logger() should preserve errno.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.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>
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>
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 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>
Don't use conn->id for privilege checks, but domain_is_unprivileged().
This is part of XSA-326.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
A guest not reading its Xenstore response buffer fast enough might
pile up lots of Xenstore watch events buffered. Reduce the generated
load by dropping new events which already have an identical copy
pending.
The special events "@..." are excluded from that handling as there are
known use cases where the handler is relying on each event to be sent
individually.
This is part of XSA-326.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Add another quota for limiting the number of outstanding requests of a
guest. As the way to specify quotas on the command line is becoming
rather nasty, switch to a new scheme using [--quota|-Q] <what>=<val>
allowing to add more quotas in future easily.
Set the default value to 20 (basically a random value not seeming to
be too high or too low).
A request is said to be outstanding if any message generated by this
request (the direct response plus potential watch events) is not yet
completely stored into a ring buffer. The initial watch event sent as
a result of registering a watch is an exception.
Note that across a live update the relation to buffered watch events
for other domains is lost.
Use talloc_zero() for allocating the domain structure in order to have
all per-domain quota zeroed initially.
This is part of XSA-326 / CVE-2022-42312.
Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Julien Grall <jgrall@amazon.com>
A future modification will limit the number of outstanding requests
for a domain, where "outstanding" means that the response of the
request or any resulting watch event hasn't been consumed yet.
In order to avoid a malicious guest being capable to block other guests
by not reading watch events, add a timeout for watch events. In case a
watch event hasn't been consumed after this timeout, it is being
deleted. Set the default timeout to 20 seconds (a random value being
not too high).
In order to support to specify other timeout values in future, use a
generic command line option for that purpose:
--timeout|-w watch-event=<seconds>
This is part of XSA-326 / CVE-2022-42311.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
When removing a watched node outside of a transaction, two watch events
are being produced instead of just a single one.
When finalizing a transaction watch events can be generated for each
node which is being modified, even if outside a transaction such
modifications might not have resulted in a watch event.
This happens e.g.:
- for nodes which are only modified due to added/removed child entries
- for nodes being removed or created implicitly (e.g. creation of a/b/c
is implicitly creating a/b, resulting in watch events for a, a/b and
a/b/c instead of a/b/c only)
Avoid these additional watch events, in order to reduce the needed
memory inside Xenstore for queueing them.
This is being achieved by adding event flags to struct accessed_node
specifying whether an event should be triggered, and whether it should
be an exact match of the modified path. Both flags can be set from
fire_watches() instead of implying them only.
This is part of XSA-326.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Julien Grall
Jason Andryuk
Juergen Gross