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

A flaw was found in the Linux kernel's iouring subsystem. In certain race conditions during event notification handling, memory structures are released prematurely before other kernel tasks finish accessing them. A local attacker could exploit this flaw to corrupt kernel memory, potentially leadi...

DEBIAN-CVE-2025-21655

In the Linux kernel, the following vulnerability has been resolved: iouring/eventfd: ensure ioeventfdsignal defers another RCU period ioeventfddosignal is invoked from an RCU callback, but when dropping the reference to the ioevfd, it calls ioeventfdfree directly if the refcount drops to zero. Th...

CVE-2025-21655

CVE-2025-21655 in the Linux kernel’s io_uring/eventfd was fixed by deferring the freeing of the io_eventfd object to an additional RCU grace period. The issue arose because io_eventfd_do_signal() is called from an RCU callback and, when the reference to the io_ev_fd drops to zero, the code attemp...