CVE-2025-21655

Summary

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.

Impact & exploitability

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products we track (1)

Recommendation

Apply the vendor fix promptly. Open any affected product above for its exact safe version.

Official patch: https://git.kernel.org/stable/c/6b63308c28987c6010b1180c72a6db4df6c68033 ↗

Additional information

• NVD record
• https://git.kernel.org/stable/c/6b63308c28987c6010b1180c72a6db4df6c68033Patch
• https://git.kernel.org/stable/c/8efff2aa2d95dc437ab67c5b4a9f1d3f367baa10Patch
• https://git.kernel.org/stable/c/a7085c3ae43b86d4b3d1b8275e6a67f14257e3b7Patch
• https://git.kernel.org/stable/c/c9a40292a44e78f71258b8522655bffaf5753bdbPatch
• https://project-zero.issues.chromium.org/issues/388499293Advisory
• https://lists.debian.org/debian-lts-announce/2025/03/msg00001.html
• https://cert-portal.siemens.com/productcert/html/ssa-019113.html