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CVE Record

CVE-2022-50307: s390/cio: fix out-of-bounds access on cio_ignore free

In the Linux kernel, the following vulnerability has been resolved: s390/cio: fix out-of-bounds access on cio_ignore free The channel-subsystem-driver scans for newly available devices whenever device-IDs are removed from the cio_ignore list using a command such as: echo free >/proc/cio_ignore Since an I/O device scan might interfer with running I/Os, commit 172da89ed0ea ("s390/cio: avoid excessive path-verification requests") introduced an optimization to exclude online devices from the scan. The newly added check for online devices incorrectly assumes that an I/O-subchannel's drvdata points to a struct io_subchannel_private. For devices that are bound to a non-default I/O subchannel driver, such as the vfio_ccw driver, this results in an out-of-bounds read access during each scan. Fix this by changing the scan logic to rely on a driver-independent online indication. For this we can use struct subchannel->config.ena, which is the driver's requested subchannel-enabled state. Since I/Os can only be started on enabled subchannels, this matches the intent of the original optimization of not scanning devices where I/O might be running.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This is a Linux kernel flaw in IBM Z/s390 I/O device handling. When devices are removed from cio_ignore, the kernel can read outside the expected memory object if a subchannel uses a non-default driver such as vfio_ccw. The public record does not provide a CVSS score or confirmed business impact.

Executive priority

Treat this as targeted infrastructure hygiene for IBM Z/s390 Linux estates, not a broad enterprise emergency based on current evidence. Patch through normal kernel maintenance unless local s390 usage, virtualization, or device-management workflows increase exposure.

Technical view

The cio scan logic assumed an I/O subchannel drvdata pointer referenced struct io_subchannel_private. With non-default I/O subchannel drivers, that assumption can cause an out-of-bounds read during scans triggered by freeing cio_ignore entries. The fix changes the online-device check to use driver-independent subchannel config state.

Likely exposure

Exposure appears limited to Linux on s390 systems using the channel-subsystem driver and cio_ignore workflows, especially where non-default I/O subchannel drivers such as vfio_ccw are present. General non-s390 Linux deployments are not indicated by the provided sources.

Exploitation context

The bundle does not cite active exploitation, CISA KEV listing, public exploit code, or a demonstrated attack path. The described trigger is an administrative/kernel device-scan path, but required privileges and practical impact are not established in the provided evidence.

Researcher notes

Key uncertainty is impact: sources describe an out-of-bounds read, but provide no CVSS, CWE, exploitability analysis, or privilege boundary details. The relevant code path is s390 CIO scanning after cio_ignore entries are freed, with vfio_ccw named as an example affected driver context.

Mitigation direction

  • Check kernel vendor guidance for CVE-2022-50307 and applicable s390 updates.
  • Update affected Linux kernels to releases containing the referenced stable fixes.
  • Prioritize s390 hosts using cio_ignore or vfio_ccw-style non-default subchannel drivers.
  • If immediate patching is delayed, reduce unnecessary cio_ignore free operations where operationally feasible.

Validation and detection

  • Inventory Linux s390 systems and record running kernel versions.
  • Check whether cio_ignore workflows are used on those hosts.
  • Identify systems using vfio_ccw or other non-default I/O subchannel drivers.
  • Confirm installed kernels include one of the referenced stable fix commits.
Prepared
Confidence
medium
Sources
5

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
0ADP providers
4Source links

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux172da89ed0eaf9d9348f5decb86ad04c624b39d1, 172da89ed0eaf9d9348f5decb86ad04c624b39d1, 172da89ed0eaf9d9348f5decb86ad04c624b39d1unaffected
LinuxLinux5.15, 0, 5.15.78, 6.0.7, 6.1affected
Weakness

CWE details

No CWE listed

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