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net/handshake: duplicate handshake cancellations leak socket

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When a handshake request is cancelled it is removed from the
handshake_net->hn_requests list, but it is still present in the
handshake_rhashtbl until it is destroyed.

If a second cancellation request arrives for the same handshake request,
then remove_pending() will return false... and assuming
HANDSHAKE_F_REQ_COMPLETED isn't set in req->hr_flags, we'll continue
processing through the out_true label, where we put another reference on
the sock and a refcount underflow occurs.

This can happen for example if a handshake times out - particularly if
the SUNRPC client sends the AUTH_TLS probe to the server but doesn't
follow it up with the ClientHello due to a problem with tlshd.  When the
timeout is hit on the server, the server will send a FIN, which triggers
a cancellation request via xs_reset_transport().  When the timeout is
hit on the client, another cancellation request happens via
xs_tls_handshake_sync().

Add a test_and_set_bit(HANDSHAKE_F_REQ_COMPLETED) in the pending cancel
path so duplicate cancels can be detected.

Fixes: 3b3009ea8a ("net/handshake: Create a NETLINK service for handling handshake requests")
Suggested-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Scott Mayhew <smayhew@redhat.com>
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Link: https://patch.msgid.link/20251209193015.3032058-1-smayhew@redhat.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Scott Mayhew
2025-12-09 14:30:15 -05:00
committed by Paolo Abeni
parent 3e82accd3e
commit 15564bd67e
1 changed files with 5 additions and 1 deletions
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6
net/handshake/request.c
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@@ -326,7 +326,11 @@ bool handshake_req_cancel(struct sock *sk)
hn = handshake_pernet(net); hn = handshake_pernet(net);
if (hn && remove_pending(hn, req)) { if (hn && remove_pending(hn, req)) {
/* Request hadn't been accepted */ /* Request hadn't been accepted - mark cancelled */
if (test_and_set_bit(HANDSHAKE_F_REQ_COMPLETED, &req->hr_flags)) {
trace_handshake_cancel_busy(net, req, sk);
return false;
}
goto out_true; goto out_true;
} }
if (test_and_set_bit(HANDSHAKE_F_REQ_COMPLETED, &req->hr_flags)) { if (test_and_set_bit(HANDSHAKE_F_REQ_COMPLETED, &req->hr_flags)) {