CVE-2021-3782

An internal reference count is held on the buffer pool, incremented every
time a new buffer is created from the pool. The reference count is
maintained as an int; on LP64 systems this can cause the reference count to
overflow if the client creates a large number of wl_shm buffer objects, or
if it can coerce the server to create a large number of external references
to the buffer storage. With the reference count overflowing, a
use-after-free can be constructed on the wl_shm_pool tracking structure,
where values may be incremented or decremented; it may also be possible to
construct a limited oracle to leak 4 bytes of server-side memory to the
attacking client at a time.

Bugs

• <https://gitlab.freedesktop.org/wayland/wayland/-/issues/224&gt;