CVE-2023-53501: iommu/amd/iommu_v2: Fix pasid_state refcount dec hit 0 warning on pasid unbind

Severity: medium (CVSS 4.7 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-10-01 · updated 2026-06-17

Description

In the Linux kernel, the following vulnerability has been resolved: iommu/amd/iommu_v2: Fix pasid_state refcount dec hit 0 warning on pasid unbind When unbinding pasid - a race condition exists vs outstanding page faults. To prevent this, the pasid_state object contains a refcount. * set to 1 on pasid bind * incremented on each ppr notification start * decremented on each ppr notification done * decremented on pasid unbind Since refcount_dec assumes that refcount will never reach 0: the current implementation causes the following to be invoked on pasid unbind: REFCOUNT_WARN("decrement hit 0; leaking memory") Fix this issue by changing refcount_dec to refcount_dec_and_test to explicitly handle refcount=1.

Affected products

Linux kernel: from 5.15 before 5.15.132; from 5.16 before 6.1.53; from 6.2 before 6.4.16; from 6.5 before 6.5.3 — fixed in 5.15.132, 6.1.53, 6.4.16, 6.5.3

How to fix

Upgrade to a fixed version: Linux kernel 5.15.132, 6.1.53, 6.4.16, 6.5.3. Check the vendor advisory for mitigations.

References

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