CVE-2026-64523net/handshake: Take a long-lived file reference at submit

Official description

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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/22e371a93563c30ebebc576db049785e0d7fc617
• https://git.kernel.org/stable/c/685b10dd0e32c7782cead16c8cf055c609678583
• https://git.kernel.org/stable/c/b913801ad9b9a51437d84d030ec6843e08976bd6
• https://git.kernel.org/stable/c/16eaba5aa89c04eea125905bb8f988c1897f4f29
• https://git.kernel.org/stable/c/09dba37eee70d0596e26645015f1aa95a9848e9d