Bug 2536347 (CVE-2026-90240)

Summary: CVE-2026-90240 kernel: iommu/vt-d: Flush context cache with correct SID when tearing down aliases
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 IOMMU (Input/Output Memory Management Unit) / VT-d (Virtualization Technology for Directed I/O) component. When tearing down Direct Memory Access (DMA) aliases of a device, the system fails to flush the context cache with the correct Source ID (SID). This oversight can lead to the hardware using stale cached entries. In scalable mode, this could allow the IOMMU to access freed memory, potentially resulting in memory corruption or system instability.
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Description OSIDB Bzimport 2026-09-17 17:31:01 UTC 
In the Linux kernel, the following vulnerability has been resolved:

iommu/vt-d: Flush context cache with correct SID when tearing down aliases

domain_context_clear_one() and device_pasid_table_teardown() are both
invoked once per DMA alias of a device. Each function locates the context
entry using the bus/devfn pair provided by the pci_for_each_dma_alias()
callback, then calls intel_context_flush_no_pasid(), which constructs a
device-selective context-cache invalidation from info->bus and
info->devfn (that is, always the requester ID of the device itself).

As a result, for every alias other than the device’s own RID, the context
entry that was just cleared in memory is never invalidated in the context
cache. Hardware may continue using that stale cached entry. In the
scalable-mode teardown path, intel_pasid_free_table() can then free the
PASID directory still referenced by that stale entry, allowing the IOMMU
to walk freed memory.

Fix this by passing the source ID of the entry being torn down to
intel_context_flush_no_pasid(), instead of deriving it from @info.
Comment 1 gkamathe 2026-09-23 16:24:07 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-90240.mbox