Otherwise a malicious connection on a shared bus, especially the system
bus, could trick GDBus clients into processing signals sent by the
malicious connection as though they had come from the real owner of a
well-known service name.
Resolves: https://gitlab.gnome.org/GNOME/glib/-/issues/3268
Signed-off-by: Simon McVittie <smcv@collabora.com>
We will use this in a subsequent commit to prevent signals from an
impostor from being delivered to a subscriber.
To avoid message reordering leading to misleading situations, this does
not use the existing mechanism for watching bus name ownership, which
delivers the ownership changes to other main-contexts. Instead, it all
happens on the single thread used by the GDBusWorker, so the order in
which messages are received is the order in which they are processed.
[Backport to 2.66.x: fix minor conflicts]
Signed-off-by: Simon McVittie <smcv@collabora.com>
This will become confusing when we start tracking the owner of a
well-known-name sender, and it's redundant anyway. Instead, track the
1 bit of data that we actually need: whether it's a well-known name.
Strictly speaking this too is redundant, because it's syntactically
derivable from the sender, but only via extra string operations.
A subsequent commit will add a data structure to keep track of the
owner of a well-known-name sender, at which point this boolean will
be replaced by the presence or absence of that data structure.
Signed-off-by: Simon McVittie <smcv@collabora.com>
No functional change, just removing some nesting. The check for whether
signal_data->subscribers is empty changes from a conditional that tests
whether it is into an early-return if it isn't.
A subsequent commit will add additional conditions that make us consider
a SignalData to be still in use and therefore not eligible to be removed.
Signed-off-by: Simon McVittie <smcv@collabora.com>
No functional changes, except that the implicit ownership-transfer
for the rule field becomes explicit (the local variable is set to NULL
afterwards).
Signed-off-by: Simon McVittie <smcv@collabora.com>
Subsequent changes will need to access these data structures from
on_worker_message_received(). No functional change here, only moving
code around.
[Backport to 2.66.x: fix minor conflicts]
Signed-off-by: Simon McVittie <smcv@collabora.com>
A subsequent commit will need this. Copying all of g_set_str() into a
private header seems cleaner than replacing the call to it.
Helps: GNOME/glib#3268
Signed-off-by: Simon McVittie <smcv@collabora.com>
Add a note to the documentation of
`g_dbus_connection_signal_unsubscribe()`, `g_bus_unwatch_name()` and
`g_bus_unown_name()` warning about the need to continue iterating the
caller’s thread-default `GMainContext` until the
unsubscribe/unwatch/unown operation is complete.
See the previous few commits and #1515 for an idea of the insidious bugs
that can be caused by not iterating the `GMainContext` until
everything’s synchronised.
Signed-off-by: Philip Withnall <withnall@endlessm.com>
`CallDestroyNotifyData` never uses that `GMainContext`, and holding a
ref to it could cause reference count cycles if the `GMainContext` is no
longer being iterated.
Signed-off-by: Philip Withnall <withnall@endlessm.com>
Helps: #1515
This just removes a now-redundant intermediate array. This means that
the `SignalSubscriber` instances are now potentially freed a little
sooner, inside the locked segment, but they are already careful to only
call their `user_data_free_func` in the right thread. So that should not
deadlock.
Signed-off-by: Philip Withnall <withnall@endlessm.com>
Helps: #978
Instead of storing a copy of the `callback` and `user_data` from a
`SignalSubscriber` in a `SignalInstance` struct (which is the closure
for signal callback data as it’s sent from the D-Bus worker thread to
the thread which originally subscribed to a signal), store a strong
reference to the `SignalSubscriber` struct itself.
This keeps the `SignalSubscriber` alive until the emission is
complete, which ensures that the `user_data` is not freed prematurely.
It also slightly reduces the allocation size of `SignalInstance` (not
that it matters).
This is threadsafe because the fields in `SignalSubscriber` are all
immutable after construction.
Signed-off-by: Philip Withnall <withnall@endlessm.com>
Helps: #978
Tie the destruction of the `user_data` to the destruction of the
`SignalSubscriber` struct. This is tidier, and ensures that the fields
in `SignalSubscriber` are all immutable after being set, so the
structure can safely be used across threads without locking.
It doesn’t matter which thread we call `call_destroy_notify()` in, since
it always defers calling `user_data_free_func` to the user-provided
`GMainContext`.
Signed-off-by: Philip Withnall <withnall@endlessm.com>
Helps: #978
The `SignalSubscriber` structs contain the callback and `user_data` of each
subscriber to a signal, along with the `guint id` token held by that
subscriber to identify their subscription. There are one or more
`SignalSubscriber` structs for a given signal match rule, which is
represented as a `SignalData` struct.
Previously, the `SignalSubscriber` structs were stored in a `GArray` in
the `SignalData` struct, to reduce the number of allocations needed
when subscribing to a signal.
However, this means that a `SignalSubscriber` struct cannot have a
lifetime which exceeds the `SignalData` which contains it. In order to
fix the race in #978, one thread needs to be able to unsubscribe from a
signal (destroying the `SignalData` struct) while zero or more other
threads are in the process of calling the callbacks from a previous
emission of that signal (using the callback and `user_data` from zero or
more `SignalSubscriber` structs). Multiple threads could be calling
callbacks because callbacks are invoked in the `GMainContext` which
originally made a subscription, and GDBus supports subscribing to a
signal from multiple threads. In that case, the callbacks are dispatched
to multiple threads.
In order to allow the `SignalSubscriber` structs to outlive the
`SignalData` which contained their old match rule, store them in a
`GPtrArray` in the `SignalData` struct, and refcount them individually.
This commit in itself should make no functional changes to how GDBus
works, but will allow following commits to do so.
Signed-off-by: Philip Withnall <withnall@endlessm.com>
Helps: #978
With debug enabled, g_dbus_connection_call_done() will throw a
g_warning() if the call failed (on purpose or not) while trying to the
serial of a non-existant reply.
(/builds/GNOME/glib/_build/gio/tests/gdbus-connection:26921): GLib-GIO-CRITICAL **: 10:10:16.311: g_dbus_message_get_reply_serial: assertion 'G_IS_DBUS_MESSAGE (message)' failed
When compiling GLib with `-Wsign-conversion`, we get various warnings
about the atomic calls. A lot of these were fixed by
3ad375a629c91a27d0165a31f0ed298fd553de0a, but some remain. Fix them by
adding appropriate casts at the call sites.
Note that `g_atomic_int_{and,or,xor}()` actually all operate on `guint`s
rather than `gint`s (which is what the rest of the `g_atomic_int_*()`
functions operate on). I can’t find any written reasoning for this, but
assume that it’s because signedness is irrelevant when you’re using an
integer as a bit field. It’s unfortunate that they’re named a
`g_atomic_int_*()` rather than `g_atomic_uint_*()` functions.
Tested by compiling GLib as:
```
CFLAGS=-Wsign-conversion jhbuild make -ac |& grep atomic
```
I’m not going to add `-Wsign-conversion` to the set of default warnings
for building GLib, because it mostly produces false positives throughout
the rest of GLib.
Signed-off-by: Philip Withnall <withnall@endlessm.com>
Fixes: #1565
This commit changes a comment in _g_dbus_worker_do_read_cb() to be
slightly more useful. At least in my experience debugging an
intermittent unit test failure in another project, this failure
condition occurred because although g_test_dbus_down() ensures that the
session GDBusConnection has exit-on-close set to FALSE before killing
its dbus-daemon, there was still a GDBusConnection on the system bus
which hit this failed read code path, because we had
DBUS_SYSTEM_BUS_ADDRESS set to the address of the #GTestDBus daemon, to
appease libudisks.
Also, make a few other minor improvements to the docs.
Using the generic marshaller has drawbacks beyond performance. One such
drawback is that it breaks the stack unwinding from the Linux kernel due
to having unsufficient data to walk past ffi_call_unixt64. That means that
performance profiling by application developers looks grouped among
seemingly unrelated code paths.
While we can't fix the kernel unwinding here, we can provide proper
c_marshallers and va_marshallers for objects within Gio so that
performance profiling of applications is more reliable.
Related to GNOME/Initiatives#10
Right now this can only be set at construction but not read back.
That seems unnecessarily restrictive, and we'll need to read these
flags from outside of gdbusconnection.c in the next commit, so let's
just make it public.
https://gitlab.gnome.org/GNOME/glib/issues/1620
There's a race condition somewhere in GTestDBus that can result in
the next test being started at a time when g_bus_get() would still
return the connection that is in the process of closing. This can
be reproduced reasonably reliably by running the gapplication test
10K times in a loop.
Instead of relying on waiting for the weak reference to be released,
we can force the issue by clearing it.
Bug: https://bugzilla.gnome.org/show_bug.cgi?id=768996
Bug-Debian: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=894677
It incorrectly said that an error could only be returned if the GVariant
was incorrect for the D-Bus API, but that’s not true: an error will also
be returned if you call it on a closed GDBusConnection.
Clarify that, and mention the actual error codes which are returned.
Signed-off-by: Philip Withnall <withnall@endlessm.com>
Reviewed-by: nobody
The g_dbus_connection_call() documentation doesn’t make it clear that
the reply type is always a tuple.
Signed-off-by: Philip Withnall <withnall@endlessm.com>
Reviewed-by: nobody
Where we were already treating GHashTables as sets, modify them to use
the set-specific APIs g_hash_table_add() and g_hash_table_contains(), to
make that usage more obvious and less prone to being broken.
Heavily based on patches by Garrett Regier <garrettregier@gmail.com>.
Signed-off-by: Philip Withnall <withnall@endlessm.com>
https://bugzilla.gnome.org/show_bug.cgi?id=749371
g_dbus_connection_call_internal() accesses the user data it passes to
g_dbus_connection_send_message_with_reply() after the call. That data
might be freed already in the case that the callback is called
immediately.
Fix this by removing the 'serial' field from the user data altogether
and fetch the serial from the message in the callback.
https://bugzilla.gnome.org/show_bug.cgi?id=748263
Some annotations I made while trying to debug bug #781847. They
introduce no behavioural changes.
Signed-off-by: Philip Withnall <withnall@endlessm.com>
Actually, Unicode changes to this file got reverted in
2d56c49b1085ae3ad769e6b59329cf493eb0f8a1. Also, there is
"No such interface '%s'" string already, so we avoid
breaking the string freeze.
This highlighted a bug in GDBusConnection, where an interface name was
not included in a message referring to it.
Signed-off-by: Philip Withnall <withnall@endlessm.com>
https://bugzilla.gnome.org/show_bug.cgi?id=780032
If we have an input parameter (or return value) we need to use (nullable).
However, if it is an (inout) or (out) parameter, (optional) is sufficient.
It looks like (nullable) could be used for everything according to the
Annotation documentation, but (optional) is more specific.
This commit broke some tests, and I don't have the time
to fix up all the expected output, so I'll revert the changes
to the affected files for now.
This needs to be redone with the necessary test fixes.
