afs: Fix netns teardown to cancel the preallocation charger

Fix the teardown of an afs network namespace to make sure it cancels the
work item that keeps the preallocated rxrpc call/conn/peer queue charged
before incoming calls are disabled (i.e. listen 0).

Also, if net->live is false because the afs netns is being deleted, make
afs_charge_preallocation() skip charging and make afs_rx_new_call() avoid
requeuing the charger.

(This was found by AI review).

Fixes: 00e907127e ("rxrpc: Preallocate peers, conns and calls for incoming service requests")
Reported-by: Simon Horman <[email protected]>
Signed-off-by: David Howells <[email protected]>
cc: Li Daming <[email protected]>
cc: Ren Wei <[email protected]>
cc: Marc Dionne <[email protected]>
cc: Jeffrey Altman <[email protected]>
cc: [email protected]
cc: [email protected]
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

fs/afs/rxrpc.c

@@ -127,6 +127,7 @@ void afs_close_socket(struct afs_net *net)
 {
 	_enter("");
 
+	cancel_work_sync(&net->charge_preallocation_work);
 	kernel_listen(net->socket, 0);
 	flush_workqueue(afs_async_calls);
 
@@ -742,7 +743,7 @@ void afs_charge_preallocation(struct work_struct *work)
 		container_of(work, struct afs_net, charge_preallocation_work);
 	struct afs_call *call = net->spare_incoming_call;
 
-	for (;;) {
+	while (READ_ONCE(net->live)) {
 		if (!call) {
 			call = afs_alloc_call(net, &afs_RXCMxxxx, GFP_KERNEL);
 			if (!call)
@@ -792,7 +793,8 @@ static void afs_rx_new_call(struct sock *sk, struct rxrpc_call *rxcall,
 	if (!call->server)
 		trace_afs_cm_no_server(call, rxrpc_kernel_remote_srx(call->peer));
 
-	queue_work(afs_wq, &net->charge_preallocation_work);
+	if (net->live)
+		queue_work(afs_wq, &net->charge_preallocation_work);
 }
 
 /*