CVE-2026-64523

In the Linux kernel, the following vulnerability has been resolved:

net/handshake: Take a long-lived file reference at submit

handshake_nl_accept_doit() needs the file pointer backing

req->hr_sk->sk_socket to survive the window between

handshake_req_next() and the subsequent FD_PREPARE() and get_file().

The submit-side sock_hold() does not provide that. sk_refcnt keeps

struct sock alive, but struct socket is owned by sock->file: when

the consumer fputs the last file reference, sock_release() tears

the socket down regardless of any sock_hold.

Add an hr_file pointer to struct handshake_req and acquire an

explicit reference on sock->file during handshake_req_submit().

handshake_complete() and handshake_req_cancel() release the

reference on the completion-bit-winning path.

The submit error path must also release the file reference, but

after rhashtable insertion a concurrent handshake_req_cancel() can

discover the request and race the error path. Gate the error-path

cleanup -- sk_destruct restoration, fput, and request destruction

-- with test_and_set_bit(HANDSHAKE_F_REQ_COMPLETED), the same

serialization handshake_complete() and handshake_req_cancel()

already use. When cancel has already claimed ownership, the submit

error path returns without touching the request; socket teardown

handles final destruction.

The accept-side dereferences are not yet retargeted; that change

comes in the next patch.