There are situations in which a call into wl_client_destroy() can
result in a reentrant call into wl_client_destroy() - which
results in UAF / double free crashes.
For example, this can occur in the following scenario.
1. Server receives a message notifying it that a client has
disconnected (WL_EVENT_HANGUP [1])
2. This beings client destruction with a call to wl_client_destroy()
3. wl_client_destroy() kicks off callbacks as client-associated
resources are cleaned up and their destructors and destruction
signals are invoked.
4. These callbacks eventually lead to an explicit call to
wl_display_flush_clients() as the server attempts to flush
events to other connected clients.
5. Since the client has already begun destruction, when it is
reached in the iteration the flush fails wl_client_destroy()
is called again [2].
This patch guards against this reentrant condition by removing
the client from the display's client list when wl_client_destroy()
is first called. This prevents access / iteration over the client
after wl_client_destroy() is called.
In the example above, wl_display_flush_clients() will pass over
the client currently undergoing destruction and the reentrant
call is avoided.
[1] 8f499bf404/src/wayland-server.c (L342)
[2] 8f499bf404/src/wayland-server.c (L1512)
Signed-off-by: Thomas Lukaszewicz [thomaslukaszewicz@gmail.com](mailto:thomaslukaszewicz@gmail.com)
The only way to attach some data to a wl_client seems to be setting up a
destroy listener and use wl_container_of. Let's make it straight forward
to attach some data.
Having an explicit destroy callback for the user data makes managing the
user data lifetime much more convenient. All other callbacks, be they
wl_resource request listeners, destroy listeners or destructors, or
wl_client destroy listeners, can assume that the wl_client user data
still exists if it was set. Otherwise making that guarantee would be
complicated.
Co-authored-by: Pekka Paalanen <pekka.paalanen@collabora.com>
Signed-off-by: Sebastian Wick <sebastian@sebastianwick.net>
Make sure that the client destroy handler runs strictly before the
resource destroy handler, which runs strictly before the client
late-destroy handler.
Signed-off-by: Daniel Stone <daniels@collabora.com>
A late-destroy listener for a client is called after all the client's
resources have been destroyed and the destroy callbacks emitted. This
lives in parallel to the existing client destroy listener, called
immediately before the client's objects get destroyed.
Signed-off-by: Daniel Stone <daniels@collabora.com>
Fixes: wayland/wayland#207
Rather than have two versions of the macro with slightly different
interfaces, just use wl_container_of internally.
This also removes use of statement expressions, a GNU C extension.
Signed-off-by: Michael Forney <mforney@mforney.org>
With the work to add wl_resource accessors and port weston to use them,
we're ready to make wl_resource and wl_object opaque structs. We keep
wl_buffer in the header for EGL stacks to use, but don't expose it by
default. In time we'll remove it completely, but for now it provides a
transition paths for code that still uses wl_buffer.
Reviewed-by: Jason Ekstrand<jason@jlekstrand.net>
It was failing with missing include files.
While here, destroy the ugly "../src/..." include
paths used in the tests that was just hacking around
this problem in the Makefile:
sed -i s/..\\/src\\/// tests/*.c
