UBUNTU-CVE-2025-21655
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.
02 / AFFECTED SOFTWARE
Affected packages
11 explicit affected versions
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16 explicit affected versions
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26 explicit affected versions
45 explicit affected versions
37 explicit affected versions
27 explicit affected versions
14 explicit affected versions
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11 explicit affected versions
17 explicit affected versions
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7 explicit affected versions
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13 explicit affected versions
43 explicit affected versions
10 explicit affected versions
8 explicit affected versions
21 explicit affected versions
14 explicit affected versions
4 explicit affected versions
78 explicit affected versions
11 explicit affected versions
1 explicit affected versions
16 explicit affected versions
03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
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.
05 / REFERENCES
Further evidence
- https://git.kernel.org/linus/c9a40292a44e78f71258b8522655bffaf5753bdb
- https://git.kernel.org/stable/c/6b63308c28987c6010b1180c72a6db4df6c68033
- https://git.kernel.org/stable/c/8efff2aa2d95dc437ab67c5b4a9f1d3f367baa10
- https://git.kernel.org/stable/c/a7085c3ae43b86d4b3d1b8275e6a67f14257e3b7
- https://git.kernel.org/stable/c/c9a40292a44e78f71258b8522655bffaf5753bdb
- https://ubuntu.com/security/CVE-2025-21655
- https://ubuntu.com/security/notices/USN-7379-1
- https://ubuntu.com/security/notices/USN-7379-2
- https://ubuntu.com/security/notices/USN-7380-1
- https://ubuntu.com/security/notices/USN-7381-1
- https://ubuntu.com/security/notices/USN-7382-1
- https://ubuntu.com/security/notices/USN-7513-1
- https://ubuntu.com/security/notices/USN-7513-2
- https://ubuntu.com/security/notices/USN-7513-3
- https://ubuntu.com/security/notices/USN-7513-4
- https://ubuntu.com/security/notices/USN-7513-5
- https://ubuntu.com/security/notices/USN-7514-1
- https://ubuntu.com/security/notices/USN-7515-1
- https://ubuntu.com/security/notices/USN-7515-2
- https://ubuntu.com/security/notices/USN-7522-1
- https://ubuntu.com/security/notices/USN-7523-1
- https://ubuntu.com/security/notices/USN-7524-1
- https://www.cve.org/CVERecord?id=CVE-2025-21655