CVE-2025-21655 – Linux Kernel io_uring EventFD RCU Refcount Vulnerability

CVE ID : CVE-2025-21655

Published : Jan. 20, 2025, 2:15 p.m. | 10 hours, 49 minutes ago

Description : In the Linux kernel, the following vulnerability has been resolved:

io_uring/eventfd: ensure io_eventfd_signal() defers another RCU period

io_eventfd_do_signal() is invoked from an RCU callback, but when
dropping the reference to the io_ev_fd, it calls io_eventfd_free()
directly if the refcount drops to zero. This isn’t correct, as any
potential freeing of the io_ev_fd should be deferred another RCU grace
period.

Just call io_eventfd_put() rather than open-code the dec-and-test and
free, which will correctly defer it another RCU grace period.

Severity: 0.0 | NA

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CVE-2025-21655 – Linux Kernel io_uring EventFD RCU Refcount Vulnerability