Bug 2531052 (CVE-2026-80920)

Summary: CVE-2026-80920 kernel: io_uring: defer eventfd signaling when queued from a wakeup handler
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's io_uring subsystem. This vulnerability occurs when the system attempts to signal an event while holding a lock, which can lead to a recursive signaling loop. This improper handling of event notifications can cause the system to become unresponsive, resulting in a denial of service (DoS).
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-09-09 16:35:01 UTC 
In the Linux kernel, the following vulnerability has been resolved:

io_uring: defer eventfd signaling when queued from a wakeup handler

io_req_local_work_add() signals the CQ ring eventfd inline when it is the
one to push the first entry onto ->work_list. For DEFER_TASKRUN rings that
add is frequently done from a waitqueue wakeup handler, where an
arbitrary waitqueue lock is held.

eventfd_signal_mask() only refuses to recurse when current->in_eventfd
is set, but that bit is set by eventfd_signal_mask() itself. If the wake
chain starts somewhere else, signal goes out inline and can feed back
into epoll.

Add IOU_F_TWQ_IN_WAKE, set it on the task_work add done from the three
waitqueue callbacks, and use it to force io_eventfd_signal() down the
existing call_rcu_hurry() deferral instead of signaling inline.
Comment 1 gkamathe 2026-09-10 04:51:53 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-80920.mbox