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

SUNRPC: wait for in-flight client TLS handshake callback

xs tls handshake sync() gives xs tls handshake done() a reference to the lower transport before submitting the handshake request. On timeout or signal, the synchronous waiter drops that reference after calling tls handshake cancel().

handshake req cancel() returns false when handshake complete() has already marked the request complete. In that case the completion callback can still be running, so dropping the callback-owned reference in the waiter can free the lower transport before xs tls handshake done() stores xprt err or drops its own reference.

If cancellation loses to completion, wait until xs tls handshake done() signals handshake done and let the callback release its reference. This mirrors the server-side handshake lifetime handling and keeps the timeout or signal return value unchanged.