CVE-2025-38566sunrpc: fix handling of server side tls alerts

Official description

In the Linux kernel, the following vulnerability has been resolved: sunrpc: fix handling of server side tls alerts Scott Mayhew discovered a security exploit in NFS over TLS in tls_alert_recv() due to its assumption it can read data from the msg iterator's kvec.. kTLS implementation splits TLS non-data record payload between the control message buffer (which includes the type such as TLS aler or TLS cipher change) and the rest of the payload (say TLS alert's level/description) which goes into the msg payload buffer. This patch proposes to rework how control messages are setup and used by sock_recvmsg(). If no control message structure is setup, kTLS layer will read and process TLS data record types. As soon as it encounters a TLS control message, it would return an error. At that point, NFS can setup a kvec backed msg buffer and read in the control message such as a TLS alert. Msg iterator can advance the kvec pointer as a part of the copy process thus we need to revert the iterator before calling into the tls_alert_recv.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/b1df394621710b312f0393e3f240fdac0764f968
• https://git.kernel.org/stable/c/25bb3647d30a20486b5fe7cff2b0e503c16c9692
• https://git.kernel.org/stable/c/3b549da875414989f480b66835d514be80a0bd9c
• https://git.kernel.org/stable/c/6b33c31cc788073bfbed9297e1f4486ed73d87da
• https://git.kernel.org/stable/c/bee47cb026e762841f3faece47b51f985e215edb