CVE-2026-46330

A flaw was found in the Linux kernel's TCP User-Level Protocol (ULP) support for SMC. This vulnerability arises when an active TCP socket is converted into an SMC socket, as the implementation attempts to modify core Virtual File System (VFS) structures in-place. This action violates fundamental VFS invariants, leading to a risk of use-after-free errors and general system instability.

The SMC TCP ULP implementation attempted to convert an already open TCP socket into an SMC socket by modifying the underlying struct file, private_data, inode, and dentry state in place. This violates VFS lifetime and identity assumptions for open files and can create use-after-free conditions or general kernel instability when later close, fput, dput, or socket paths operate on stale or mismatched objects. For the CVSS the PR:L is used because a local unprivileged process may be able to create a TCP socket and request the smc TCP ULP on its own file descriptor when the feature is available. The issue is not directly network reachable because the dangerous operation is a local socket control operation rather than remote packet processing. Impact is at least local denial of service via kernel crash, and potentially it may allow confidentiality or integrity impact due to UAF style memory corruption and should be reviewed manually.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this issue, prevent module smc from being loaded. Please see https://access.redhat.com/solutions/41278 for how to blacklist a kernel module to prevent it from loading automatically.