srcu: Don't queue workqueue handlers to never-online CPUs

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Summary

CVECVE-2026-64211
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-24 16:16:48 UTC
Updated2026-07-24 16:16:48 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: srcu: Don't queue workqueue handlers to never-online CPUs While an srcu_struct structure is in the midst of switching from CPU-0 to all-CPUs state, it can attempt to invoke callbacks for CPUs that have never been online. Worse yet, it can attempt in invoke callbacks for CPUs that never will be online, even including imaginary CPUs not in cpu_possible_mask. This can cause hangs on s390, which is not set up to deal with workqueue handlers being scheduled on such CPUs. This commit therefore causes Tree SRCU to refrain from queueing workqueue handlers on CPUs that have not yet (and might never) come online. Because callbacks are not invoked on CPUs that have not been online, it is an error to invoke call_srcu(), synchronize_srcu(), or synchronize_srcu_expedited() on a CPU that is not yet fully online. However, it turns out to be less code to redirect the callbacks from too-early invocations of call_srcu() than to warn about such invocations. This commit therefore also redirects callbacks queued on not-yet-fully-online CPUs to the boot CPU.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 61bbcfb50514a8a94e035a7349697a3790ab4783 a4153538fcd2361c4e0039eb103265492d26044e git Not specified
CNA Linux Linux affected 61bbcfb50514a8a94e035a7349697a3790ab4783 593889c401426004bd0ea0f6d4fcece728b03420 git Not specified
CNA Linux Linux affected 7.0 Not specified
CNA Linux Linux unaffected 7.0 semver Not specified
CNA Linux Linux unaffected 7.0.11 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/593889c401426004bd0ea0f6d4fcece728b03420 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/a4153538fcd2361c4e0039eb103265492d26044e 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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