CVE-2026-63979

Status: UPDATED  |  Advisory ID: CVE-2026-63979

Key Details

Affected Products, Subsystems & Sectors

What to Know

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

net/handshake: hand off the pinned file reference to accept_doit

handshake_req_next() removes the request from the per-net

pending list and drops hn_lock before handshake_nl_accept_doit()

reads req->hr_sk->sk_socket and dereferences sock->file (once in

FD_PREPARE() and again in get_file()). In that window a

consumer running tls_handshake_cancel() followed by sockfd_put()

(svc_sock_free) or __fput_sync() (xs_reset_transport) releases

sock->file. sock_release() then runs sock_orphan(), zeroing

sk_socket, and frees the struct socket. The accept-side code

either reads NULL through sk_socket or chases freed memory.

The submit-side sock_hold() does not prevent this. sk_refcnt

protects struct sock, but struct socket and sock->file are

independently refcounted via the file descriptor the consumer

owns. Pinning sk leaves sock and sock->file unprotected.

Retarget the accept-side dereferences at req->hr_file, which was

pinned at submit time, instead of req->hr_sk->sk_socket->file.

Pinning on its own is not sufficient: a consumer that cancels

between handshake_req_next() returning and accept_doit reaching

FD_PREPARE() takes the !remove_pending() branch in

handshake_req_cancel() and drops hr_file before the accept side

takes its own reference. Hand off an additional file reference

inside handshake_req_next(), under hn_lock, so the accept side

operates on a reference that no concurrent handshake_req_cancel()

can revoke. FD_PREPARE() consumes that handed-off reference,

either by transferring it to the new fd in fd_publish() or by

dropping it in the cleanup destructor on error; the explicit

get_file() that previously balanced FD_PREPARE() is therefore

redundant and goes away.

Update handshake_req_cancel_test2 and _test3 to simulate the

FD_PREPARE() consumption with an fput() so the kunit file-count

assertions stay balanced. (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References