CVE-2022-50728
Unknown Unknown - Not Provided

Function Pointer Type Mismatch in Linux s390 lcs Driver Causes Kernel Panic

Publication date: 2025-12-24

Last updated on: 2025-12-24

Assigner: kernel.org

Description
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.

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Meta Information

Published
2025-12-24
Last Modified
2025-12-24
Generated
2026-07-06
AI Q&A
2025-12-24
EPSS Evaluated
2026-07-05
NVD
CVE-2022-50728

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
linux kernel *
linux linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability involves a mismatch in the return type of the function lcs_start_xmit() in the Linux kernel's s390 network driver. The function was returning an int type, but it should return netdev_tx_t as expected by the ndo_start_xmit() function pointer in struct net_device_ops. This mismatch can cause kernel control flow integrity (kCFI) failures when using clang's kCFI feature, potentially leading to kernel panics or thread termination. The fix adjusts the return type of lcs_start_xmit() to match the expected prototype, preventing these runtime failures.

Impact Analysis

If the return type mismatch is not fixed, and the kernel is compiled with clang's kernel control flow integrity (kCFI) enabled, it can cause runtime failures such as kernel panics or threads being killed. This can lead to system instability or crashes on systems using the s390 network driver, impacting availability and reliability.

Mitigation Strategies

To mitigate this vulnerability, update the Linux kernel to a version where the return type of lcs_start_xmit() in the s390/lcs driver has been corrected to match the expected netdev_tx_t return type. This fix resolves the kernel control flow integrity (kCFI) failure and prevents potential kernel panics or thread kills related to this issue.

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