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CVE Record

CVE-2022-50728: s390/lcs: Fix return type of lcs_start_xmit()

In the Linux kernel, the following vulnerability has been resolved: s390/lcs: Fix return type of lcs_start_xmit() With clang's kernel control flow integrity (kCFI, CONFIG_CFI_CLANG), indirect call targets are validated against the expected function pointer prototype to make sure the call target is valid to help mitigate ROP attacks. If they are not identical, there is a failure at run time, which manifests as either a kernel panic or thread getting killed. A proposed warning in clang aims to catch these at compile time, which reveals: drivers/s390/net/lcs.c:2090:21: error: incompatible function pointer types initializing 'netdev_tx_t (*)(struct sk_buff *, struct net_device *)' (aka 'enum netdev_tx (*)(struct sk_buff *, struct net_device *)') with an expression of type 'int (struct sk_buff *, struct net_device *)' [-Werror,-Wincompatible-function-pointer-types-strict] .ndo_start_xmit = lcs_start_xmit, ^~~~~~~~~~~~~~ drivers/s390/net/lcs.c:2097:21: error: incompatible function pointer types initializing 'netdev_tx_t (*)(struct sk_buff *, struct net_device *)' (aka 'enum netdev_tx (*)(struct sk_buff *, struct net_device *)') with an expression of type 'int (struct sk_buff *, struct net_device *)' [-Werror,-Wincompatible-function-pointer-types-strict] .ndo_start_xmit = lcs_start_xmit, ^~~~~~~~~~~~~~ ->ndo_start_xmit() in 'struct net_device_ops' expects a return type of 'netdev_tx_t', not 'int'. Adjust the return type of lcs_start_xmit() to match the prototype's to resolve the warning and potential CFI failure, should s390 select ARCH_SUPPORTS_CFI_CLANG in the future.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysislow

Security readout for executives and security teams

Plain-English summary

This CVE is a Linux kernel correctness issue in the IBM s390 LCS network driver. The driver used a function return type that did not match the kernel networking interface. Under clang kernel CFI, that mismatch could trigger a runtime failure such as a kernel panic. Exposure appears narrow and no active exploitation is reported in the provided sources.

Executive priority

Treat as a targeted maintenance item, not an emergency. Prioritize only if the organization runs Linux on IBM Z or s390 environments with LCS networking. Otherwise, track through normal kernel patch cycles.

Technical view

The s390 lcs_start_xmit() implementation returned int while net_device_ops.ndo_start_xmit expects netdev_tx_t. With CONFIG_CFI_CLANG, indirect call prototype validation can fail at runtime. The upstream fix changes the function return type to match the expected prototype. The CVE lists multiple affected Linux kernel branches and stable commit references.

Likely exposure

Most relevant to Linux systems on s390/s390x using the LCS network driver, especially kernels built with clang kCFI. General Linux fleets without s390 LCS exposure are unlikely to be affected based on the provided description.

Exploitation context

The provided sources do not report exploitation, public exploit activity, or KEV listing. The described impact is a potential CFI runtime failure, not a documented remote compromise path. Evidence points to a configuration- and architecture-specific stability risk.

Researcher notes

The CVE data gives no CVSS, CWE, or exploitation evidence. The issue is a type mismatch affecting CFI validation behavior. The description suggests s390 CFI support was prospective, so real-world impact depends on kernel branch, architecture, driver use, and build configuration.

Mitigation direction

  • Check Linux distribution advisories for CVE-2022-50728 applicability and kernel updates.
  • Update affected kernels to a release containing the referenced stable fix.
  • Prioritize s390/s390x systems using the LCS network driver.
  • If no vendor package is available, follow vendor kernel backport guidance.

Validation and detection

  • Inventory Linux systems running on s390 or s390x architecture.
  • Identify kernels in the affected version ranges from the CVE record.
  • Confirm whether the LCS network driver is present or used.
  • Verify the vendor kernel includes one of the referenced stable commits.
  • Review kernel build configuration for clang kCFI relevance.
Prepared
Confidence
high
Sources
11

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

Conservative CVE-to-ATT&CK context

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CVE-2022-50728 mapping review

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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
0Timeline events
0ADP providers
10Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxdc1f8bf68b311b1537cb65893430b6796118498a, dc1f8bf68b311b1537cb65893430b6796118498a, dc1f8bf68b311b1537cb65893430b6796118498a, dc1f8bf68b311b1537cb65893430b6796118498a, dc1f8bf68b311b1537cb65893430b6796118498a, dc1f8bf68b311b1537cb65893430b6796118498a, dc1f8bf68b311b1537cb65893430b6796118498a, dc1f8bf68b311b1537cb65893430b6796118498a, dc1f8bf68b311b1537cb65893430b6796118498aunaffected
LinuxLinux2.6.32, 0, 4.9.337, 4.14.303, 4.19.270, 5.4.229, 5.10.163, 5.15.86, 6.0.16, 6.1.2, 6.2affected
Weakness

CWE details

No CWE listed

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