The Redox article is underselling it somewhat. Part of the problem is Linux's historical syscall restriction systems (seccomp) did not (does not?) apply to io_uring, so io_uring is (was?) all or nothing on async versions of syscalls it implements. Also, io_uring is rapidly adding API surface compared to other parts of the kernel. With these factors combined, it has had repeated security problems since 2019 and has lead to, e.g., Android disabling io_uring entirely for applications.
> in the past year, there has been a clear trend: 60% of the submissions exploited the io_uring component of the Linux kernel (we paid out around 1 million USD for io_uring alone). Furthermore, io_uring vulnerabilities were used in all the submissions which bypassed our mitigations.
https://security.googleblog.com/2023/06/learnings-from-kctf-...
> in the past year, there has been a clear trend: 60% of the submissions exploited the io_uring component of the Linux kernel (we paid out around 1 million USD for io_uring alone). Furthermore, io_uring vulnerabilities were used in all the submissions which bypassed our mitigations.