net/tls: Fix sk_psock refcnt leak in bpf_exec_tx_verdict()

bpf_exec_tx_verdict() invokes sk_psock_get(), which returns a reference
of the specified sk_psock object to "psock" with increased refcnt.

When bpf_exec_tx_verdict() returns, local variable "psock" becomes
invalid, so the refcount should be decreased to keep refcount balanced.

The reference counting issue happens in one exception handling path of
bpf_exec_tx_verdict(). When "policy" equals to NULL but "psock" is not
NULL, the function forgets to decrease the refcnt increased by
sk_psock_get(), causing a refcnt leak.

Fix this issue by calling sk_psock_put() on this error path before
bpf_exec_tx_verdict() returns.
Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tls/tls_sw.c

@@ -800,6 +800,8 @@ static int bpf_exec_tx_verdict(struct sk_msg *msg, struct sock *sk,
 			*copied -= sk_msg_free(sk, msg);
 			tls_free_open_rec(sk);
 		}
+		if (psock)
+			sk_psock_put(sk, psock);
 		return err;
 	}
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