In the Linux kernel before 5.4.2, the io_uring feature leads to requests
that inadvertently have UID 0 and full capabilities, aka CID-181e448d8709.
This is related to fs/io-wq.c, fs/io_uring.c, and net/socket.c. For
example, an attacker can bypass intended restrictions on adding an IPv4
address to the loopback interface. This occurs because IORING_OP_SENDMSG
operations, although requested in the context of an unprivileged user, are
sometimes performed by a kernel worker thread without considering that
context.

It was discovered that the IO uring implementation in the Linux kernel did
not properly perform credentials checks in certain situations. A local
attacker could possibly use this to gain administrative privileges.