CVE-2022-50728: 
Linux Kernel vulnerability analysis and mitigation

CVE-2022-50728 is a vulnerability in the Linux kernel's s390/lcs (LAN Channel Station) network driver, caused by an incorrect return type in the lcs_start_xmit() function. The function returns int instead of the required netdev_tx_t (enum netdev_tx), creating an incompatible function pointer type mismatch. This issue was published on December 24, 2025, and affects multiple stable Linux kernel versions. The estimated CVSS severity is Medium (Feedly, CVE.org).

The root cause is an incompatible function pointer type (related to CWE-704: Incorrect Type Conversion or Cast) in drivers/s390/net/lcs.c. The lcs_start_xmit() function is assigned to the .ndo_start_xmit callback in the network device operations structure, but its declared return type is int rather than the expected netdev_tx_t (an enum). With Clang's kernel Control Flow Integrity (kCFI, CONFIG_CFI_CLANG) enabled, indirect call targets are validated against the expected function pointer prototype at runtime; a mismatch causes a kernel panic or thread termination. The fix involves correcting the return type of lcs_start_xmit() to netdev_tx_t to match the ndo_start_xmit prototype (Feedly, CVE.org).

The primary impact is an availability risk: on kernels compiled with CONFIG_CFI_CLANG, the type mismatch can trigger a kernel panic or cause threads to be killed when the s390 LCS network driver's transmit function is invoked, resulting in denial of service on affected s390 systems. Confidentiality and integrity are not directly impacted by this vulnerability. The scope is limited to Linux systems running on IBM s390 hardware with the LCS network driver and Clang CFI enabled (Feedly).

The fix has been applied to multiple Linux kernel stable branches via patches to drivers/s390/net/lcs.c, correcting the return type of lcs_start_xmit() to netdev_tx_t. Users should update to a patched kernel version that includes the relevant commits (e.g., commits 5ad774fb823c, 7b4da3fcd513, 20022d551f20, 69669820844f, bb16db839365 in the stable kernel tree). SUSE has also issued advisories (SUSE-2026-0263-1, SUSE-2026-0317-1, SUSE-2026-0411-1) addressing this CVE in their kernel packages (Feedly, Linux Security). As a workaround, systems not requiring the LCS driver can blacklist the lcs kernel module, or avoid building kernels with CONFIG_CFI_CLANG until patched.

SUSE has issued multiple kernel security advisories addressing CVE-2022-50728 as part of broader kernel update batches. Tenable has added detection for this CVE in Nessus (plugin 279880) and its pipeline. No significant independent researcher commentary or social media discussion has been identified for this vulnerability (Feedly, Tenable).