KVM: arm64: vgic: Fix race between LPI release and re-registration

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Summary

CVECVE-2026-74568
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-15 13:18:02 UTC
Updated2026-08-15 13:18:02 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: KVM: arm64: vgic: Fix race between LPI release and re-registration Fix a potential race between decrementing an LPI's reference count and evicting that structure from the LPI xarray. LPI structures are maintained in the VGIC LPI xarray (dist->lpi_xa). When the reference count of an LPI structure drops to zero, vgic_release_lpi_locked() removes the structure from the xarray and frees it under the xarray lock. However, the release of an LPI can race with a concurrent LPI re-registration with the same INTID via vgic_add_lpi() on another CPU, since the reference count drop and the xarray eviction are not performed in a single atomic step. This can happen e.g. if the guest issues a DISCARD while the LPI is still referenced from a vCPU's active-pending list (ap_list), and the same INTID is re-mapped via MAPTI. Particularly, vgic_release_lpi_locked() is called from two distinct paths: direct release via vgic_put_irq(), and deferred release via vgic_release_deleted_lpis(). During direct release, the issue can result in deleting a newly registered LPI from the xarray: CPU0 (Releasing LPI) CPU1 (Adding new LPI) ==================== ===================== vgic_put_irq() __vgic_put_irq() refcount_dec_and_test() vgic_add_lpi() xa_lock_irqsave() old_irq = xa_load(.., intid) vgic_try_get_irq_ref(old_irq) == false new IRQ inserted --> __xa_store(.., intid, ..) xa_unlock_irqrestore() xa_lock_irqsave(); vgic_release_lpi_locked() __xa_erase(.., irq->intid) <-- BUG: new IRQ is erased kfree_rcu(old_irq) During the deferred release path, the old IRQ can be leaked: CPU0 (Releasing LPI) CPU1 (Adding new LPI) ==================== ===================== vgic_put_irq_norelease() __vgic_put_irq() refcount_dec_and_test() irq->pending_release = true vgic_add_lpi() xa_lock_irqsave() old_irq = xa_load(.., intid) vgic_try_get_irq_ref(oldirq) == false BUG: old IRQ overwritten --> __xa_store(.., intid, ..) xa_unlock_irqrestore() vgic_release_deleted_lpis() xa_lock_irqsave() xa_for_each() { .. } <-- old IRQ with pending_release = true is gone, so it cannot be released To fix the direct release path, move the reference count drop inside the xarray lock, making sure that vgic_add_lpi() never encounters the to-be-released LPI. In the deferred release path, the refcount drop must happen under a raw spinlock, so the xarray lock cannot be grabbed, and the same solution does not work. Instead, update vgic_add_lpi(), so that if it evicts an LPI from the xarray, it takes on the responsibility of freeing it. Consequently, an LPI may now be freed concurrently after a deferred release drops the refcount, so accessing the pending_release field is no longer safe from use-after-free. Delete all uses of the flag, and update vgic_release_deleted_lpis() to identify orphaned LPIs purely based on their refcount.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 3a08a6ca7c373198c84e2a8c025c395ee966ff8a 292e80a159aa88635bf668a7212cfdf526b8bd52 git Not specified
CNA Linux Linux affected 3a08a6ca7c373198c84e2a8c025c395ee966ff8a cbfe2b24a1ea9de35032dbdd100fdc700f5be92d git Not specified
CNA Linux Linux affected 6.17 Not specified
CNA Linux Linux unaffected 6.17 semver Not specified
CNA Linux Linux unaffected 7.1.8 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2-rc6 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/292e80a159aa88635bf668a7212cfdf526b8bd52 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/cbfe2b24a1ea9de35032dbdd100fdc700f5be92d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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