6.6-stable review patch. If anyone has any objections, please let me know.
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From: Scott Mayhew smayhew@redhat.com
[ Upstream commit 15564bd67e2975002f2a8e9defee33e321d3183f ]
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: 3b3009ea8abb ("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 Signed-off-by: Sasha Levin sashal@kernel.org --- net/handshake/request.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/net/handshake/request.c b/net/handshake/request.c index 94d5cef3e048b..0ac126b0add60 100644 --- a/net/handshake/request.c +++ b/net/handshake/request.c @@ -325,7 +325,11 @@ bool handshake_req_cancel(struct sock *sk)
hn = handshake_pernet(net); 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; } if (test_and_set_bit(HANDSHAKE_F_REQ_COMPLETED, &req->hr_flags)) {