tipc: fix a potential deadlock on &tx->lock

It seems that tipc_crypto_key_revoke() could be be invoked by
wokequeue tipc_crypto_work_rx() under process context and
timer/rx callback under softirq context, thus the lock acquisition
on &tx->lock seems better use spin_lock_bh() to prevent possible
deadlock.

This flaw was found by an experimental static analysis tool I am
developing for irq-related deadlock.

tipc_crypto_work_rx() <workqueue>
--> tipc_crypto_key_distr()
--> tipc_bcast_xmit()
--> tipc_bcbase_xmit()
--> tipc_bearer_bc_xmit()
--> tipc_crypto_xmit()
--> tipc_ehdr_build()
--> tipc_crypto_key_revoke()
--> spin_lock(&tx->lock)
<timer interrupt>
   --> tipc_disc_timeout()
   --> tipc_bearer_xmit_skb()
   --> tipc_crypto_xmit()
   --> tipc_ehdr_build()
   --> tipc_crypto_key_revoke()
   --> spin_lock(&tx->lock) <deadlock here>

Signed-off-by: Chengfeng Ye <dg573847474@gmail.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Acked-by: Jon Maloy <jmaloy@redhat.com>
Fixes: fc1b6d6 ("tipc: introduce TIPC encryption & authentication")
Link: https://lore.kernel.org/r/20230927181414.59928-1-dg573847474@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/tipc/crypto.c

@@ -1441,14 +1441,14 @@ static int tipc_crypto_key_revoke(struct net *net, u8 tx_key)
 	struct tipc_crypto *tx = tipc_net(net)->crypto_tx;
 	struct tipc_key key;
 
-	spin_lock(&tx->lock);
+	spin_lock_bh(&tx->lock);
 	key = tx->key;
 	WARN_ON(!key.active || tx_key != key.active);
 
 	/* Free the active key */
 	tipc_crypto_key_set_state(tx, key.passive, 0, key.pending);
 	tipc_crypto_key_detach(tx->aead[key.active], &tx->lock);
-	spin_unlock(&tx->lock);
+	spin_unlock_bh(&tx->lock);
 
 	pr_warn("%s: key is revoked\n", tx->name);
 	return -EKEYREVOKED;