powerpc/hv-gpci: fix preempt count leak in sysfs show paths

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Summary

CVECVE-2026-64070
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-19 16:17:47 UTC
Updated2026-07-19 16:17:47 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: powerpc/hv-gpci: fix preempt count leak in sysfs show paths Four sysfs show() callbacks in hv-gpci take get_cpu_var(hv_gpci_reqb) (which calls preempt_disable()) but only call the matching put_cpu_var() on the error path under the 'out:' label. Every successful read leaks one preempt_disable(): processor_bus_topology_show() processor_config_show() affinity_domain_via_virtual_processor_show() affinity_domain_via_domain_show() (affinity_domain_via_partition_show() was already correct.) On a CONFIG_PREEMPT=y kernel, repeated reads raise preempt_count and eventually return to userspace with preemption still disabled. The next user-mode page fault then hits faulthandler_disabled() == 1, gets forced to SIGSEGV, and the resulting coredump trips 'BUG: scheduling while atomic' in call_usermodehelper_exec -> wait_for_completion_state -> schedule: BUG: scheduling while atomic: <task>/<pid>/0x00000004 ... __schedule_bug+0x6c/0x90 __schedule+0x58c/0x13a0 schedule+0x48/0x1a0 schedule_timeout+0x104/0x170 wait_for_completion_state+0x16c/0x330 call_usermodehelper_exec+0x254/0x2d0 vfs_coredump+0x1050/0x2590 get_signal+0xb9c/0xc80 do_notify_resume+0xf8/0x470 Add an out_success label that calls put_cpu_var() before returning the byte count, mirroring affinity_domain_via_partition_show().

Risk And Classification

EPSS: 0.001550000 probability, percentile 0.051010000 (date 2026-07-20)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 71f1c39647d8c9d4d54a861ec81f1ff17544bcb6 903409000a07ac8e31ffedeb8516f4f8d67150c8 git Not specified
CNA Linux Linux affected 71f1c39647d8c9d4d54a861ec81f1ff17544bcb6 dbc30a57bd8e026995e9fa8e8c31cffd18542c01 git Not specified
CNA Linux Linux affected 6.6 Not specified
CNA Linux Linux unaffected 6.6 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/903409000a07ac8e31ffedeb8516f4f8d67150c8 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/dbc30a57bd8e026995e9fa8e8c31cffd18542c01 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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